LIMSWiki - User contributions [en]

Vendor:Calorimeter vendor

2011-07-11T20:45:03Z

Abouilly: /* Calorimeter vendors */

A '''calorimeter vendor''' is an entity (business, company, corporation, etc.) which manufactures and/or distributes [[Calorimeter|calorimeters]].

== Calorimeter vendors ==

{| class="sortable" id="Calorimeter_vendor" border="1" cellpadding="5" cellspacing="0"
! Vendor
! Product Name
! Headquarters (Country)
! Active? (Yes/No/Unknown)
! Additional Notes

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| ARELCO
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| C-3 Analysentechnick GmbH
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| CAL 2K
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| ELVETEC SERVICES
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| ENTEC ENVIRONMENTAL TECHNOLOGY Ges
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| EQUILABO
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| EQUIPEMENTS SCIENTIFIQUES
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| FISHER SCIENTIFIC
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| GE Healthcare
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| GENTEC-E
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| HEL
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| IKA
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| LASER 2000
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| LAUDA France
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| LECO Corporation
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| LINSEIS
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| MAC TECHNOLOGIE
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| METTLER TOLEDO
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| MicroCal
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| NETZSCH
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| PARR Instrument
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| PerkinElmer,Inc
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| PETROTEST France
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| REAKTON
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| SETARAM Instrumentation
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| TA Instruments
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| Thermo Scientific
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| VWR INTERNATIONAL
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|}

== References ==
<references />


[[Category:Vendor classes]]

Calorimeter

2011-07-07T17:24:20Z

Abouilly: Edited article.

== Headline text ==
''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation].

Then Cp = \frac {W\Delta H}{M\Delta T}

where

:Cp = Specific heat at constant pressure
:\Delta H = Enthalpy of solution
:\Delta T = Change in temperature
:W = mass of solute
:M = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

Delta T = K {dq\over dt} = K C_p\, \beta

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

{dq\over dt} = C_p \beta + f(t,T)

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in
[http://en.wikipedia.org/wiki/Polymer?title=Polymer polymer] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often
[http://en.wikipedia.org/wiki/Gold?title=Gold Gold], or Gold plated steel), and which will be able to withstand
[http://en.wikipedia.org/wiki/Pressure?title=Pressure pressure] (typically up to 100
[http://en.wikipedia.org/wiki/Bar_(unit)?title=Bar bar]). The presence of an
[http://en.wikipedia.org/wiki/Exothermic?title=Exothermic exothermic] event can then be used to assess the
[http://en.wikipedia.org/wiki/Chemical_stability?title=Stability stability] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn
[http://en.wikipedia.org/wiki/Activation_energy?title=ActivationEnergy activation energy], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from
[http://en.wikipedia.org/wiki/Ambient_temperature?title=Ambient ambient] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Isothermal_Titration_Calorimetry?title=ISC Isothermal Titration Calorimetry]
In an '''isothermal.

[http://en.wikipedia.org/wiki/Titration?title=Titration titration] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point (
[http://en.wikipedia.org/wiki/Stoichiometry?title=Stoichiometry stoichiometry]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of
[http://en.wikipedia.org/wiki/Biochemistry?title=Biochemistry biochemistry], because it facilitates determination of substrate binding to
[http://en.wikipedia.org/wiki/Enzyme?title=Enzyme enzyme]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==Calorimeter vendors==
See the [[Calorimeter vendor]] page for a list of LIMS vendors past and present.

==See also==
*[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy Enthalpy]
*[http://en.wikipedia.org/wiki/Heat?title=Heat Heat]
*[http://en.wikipedia.org/wiki/Calorie?title=Calorie Calorie]
*[http://en.wikipedia.org/wiki/Heat_of_combustion?title=HeatOfCombustion Heat of combustion]
*[http://en.wikipedia.org/wiki/Calorimeter_constant?title=CalorimeterConstant Calorimeter constant]

==References==
[http://en.wikipedia.org/wiki/Calorimeter Wikipedia]

[[Category:Analytical]]

Calorimeter

2011-07-06T12:52:18Z

Abouilly: Edited article.

== Headline text ==
''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation].

Then Cp = \frac {W\Delta H}{M\Delta T}

where

:Cp = Specific heat at constant pressure
:\Delta H = Enthalpy of solution
:\Delta T = Change in temperature
:W = mass of solute
:M = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

Delta T = K {dq\over dt} = K C_p\, \beta

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

{dq\over dt} = C_p \beta + f(t,T)

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in
[http://en.wikipedia.org/wiki/Polymer?title=Polymer polymer] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often
[http://en.wikipedia.org/wiki/Gold?title=Gold Gold], or Gold plated steel), and which will be able to withstand
[http://en.wikipedia.org/wiki/Pressure?title=Pressure pressure] (typically up to 100
[http://en.wikipedia.org/wiki/Bar_(unit)?title=Bar bar]). The presence of an
[http://en.wikipedia.org/wiki/Exothermic?title=Exothermic exothermic] event can then be used to assess the
[http://en.wikipedia.org/wiki/Chemical_stability?title=Stability stability] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn
[http://en.wikipedia.org/wiki/Activation_energy?title=ActivationEnergy activation energy], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from
[http://en.wikipedia.org/wiki/Ambient_temperature?title=Ambient ambient] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Isothermal_Titration_Calorimetry?title=ISC Isothermal Titration Calorimetry]
In an '''isothermal.

[http://en.wikipedia.org/wiki/Titration?title=Titration titration] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point (
[http://en.wikipedia.org/wiki/Stoichiometry?title=Stoichiometry stoichiometry]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of
[http://en.wikipedia.org/wiki/Biochemistry?title=Biochemistry biochemistry], because it facilitates determination of substrate binding to
[http://en.wikipedia.org/wiki/Enzyme?title=Enzyme enzyme]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
*[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy Enthalpy]
*[http://en.wikipedia.org/wiki/Heat?title=Heat Heat]
*[http://en.wikipedia.org/wiki/Calorie?title=Calorie Calorie]
*[http://en.wikipedia.org/wiki/Heat_of_combustion?title=HeatOfCombustion Heat of combustion]
*[http://en.wikipedia.org/wiki/Calorimeter_constant?title=CalorimeterConstant Calorimeter constant]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

[[Category:Analytical]]

Calorimeter

2011-07-05T21:33:00Z

Abouilly: Edited article.

== Headline text ==
''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation].

Then Cp = \frac {W\Delta H}{M\Delta T}

where

:Cp = Specific heat at constant pressure
:\Delta H = Enthalpy of solution
:\Delta T = Change in temperature
:W = mass of solute
:M = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

Delta T = K {dq\over dt} = K C_p\, \beta

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T)</math>

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in
[http://en.wikipedia.org/wiki/Polymer?title=Polymer polymer] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often
[http://en.wikipedia.org/wiki/Gold?title=Gold Gold], or Gold plated steel), and which will be able to withstand
[http://en.wikipedia.org/wiki/Pressure?title=Pressure pressure] (typically up to 100
[http://en.wikipedia.org/wiki/Bar_(unit)?title=Bar bar]). The presence of an
[http://en.wikipedia.org/wiki/Exothermic?title=Exothermic exothermic] event can then be used to assess the
[http://en.wikipedia.org/wiki/Chemical_stability?title=Stability stability] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn
[http://en.wikipedia.org/wiki/Activation_energy?title=ActivationEnergy activation energy], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from
[http://en.wikipedia.org/wiki/Ambient_temperature?title=Ambient ambient] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Isothermal_Titration_Calorimetry?title=ISC Isothermal Titration Calorimetry]
In an '''isothermal.

[http://en.wikipedia.org/wiki/Titration?title=Titration titration] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point (
[http://en.wikipedia.org/wiki/Stoichiometry?title=Stoichiometry stoichiometry]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of
[http://en.wikipedia.org/wiki/Biochemistry?title=Biochemistry biochemistry], because it facilitates determination of substrate binding to
[http://en.wikipedia.org/wiki/Enzyme?title=Enzyme enzyme]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
*[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy Enthalpy]
*[http://en.wikipedia.org/wiki/Heat?title=Heat Heat]
*[http://en.wikipedia.org/wiki/Calorie?title=Calorie Calorie]
*[http://en.wikipedia.org/wiki/Heat_of_combustion?title=HeatOfCombustion Heat of combustion]
*[http://en.wikipedia.org/wiki/Calorimeter_constant?title=CalorimeterConstant Calorimeter constant]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

[[Category:Analytical]]

Calorimeter

2011-07-05T20:38:07Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in
[http://en.wikipedia.org/wiki/Polymer?title=Polymer polymer] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often
[http://en.wikipedia.org/wiki/Gold?title=Gold Gold], or Gold plated steel), and which will be able to withstand
[http://en.wikipedia.org/wiki/Pressure?title=Pressure pressure] (typically up to 100
[http://en.wikipedia.org/wiki/Bar_(unit)?title=Bar bar]). The presence of an
[http://en.wikipedia.org/wiki/Exothermic?title=Exothermic exothermic] event can then be used to assess the
[http://en.wikipedia.org/wiki/Chemical_stability?title=Stability stability] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn
[http://en.wikipedia.org/wiki/Activation_energy?title=ActivationEnergy activation energy], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from
[http://en.wikipedia.org/wiki/Ambient_temperature?title=Ambient ambient] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Isothermal_Titration_Calorimetry?title=ISC Isothermal Titration Calorimetry]
In an '''isothermal.

[http://en.wikipedia.org/wiki/Titration?title=Titration titration] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point (
[http://en.wikipedia.org/wiki/Stoichiometry?title=Stoichiometry stoichiometry]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of
[http://en.wikipedia.org/wiki/Biochemistry?title=Biochemistry biochemistry], because it facilitates determination of substrate binding to
[http://en.wikipedia.org/wiki/Enzyme?title=Enzyme enzyme]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
*[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy Enthalpy]
*[http://en.wikipedia.org/wiki/Heat?title=Heat Heat]
*[http://en.wikipedia.org/wiki/Calorie?title=Calorie Calorie]
*[http://en.wikipedia.org/wiki/Heat_of_combustion?title=HeatOfCombustion Heat of combustion]
*[http://en.wikipedia.org/wiki/Calorimeter_constant?title=CalorimeterConstant Calorimeter constant]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

[[Category:Analytical]]

Calorimeter

2011-07-05T20:29:28Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in
[http://en.wikipedia.org/wiki/Polymer?title=Polymer polymer] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often
[http://en.wikipedia.org/wiki/Gold?title=Gold Gold], or Gold plated steel), and which will be able to withstand
[http://en.wikipedia.org/wiki/Pressure?title=Pressure pressure] (typically up to 100
[http://en.wikipedia.org/wiki/Bar_(unit)?title=Bar bar]). The presence of an
[http://en.wikipedia.org/wiki/Exothermic?title=Exothermic exothermic] event can then be used to assess the
[http://en.wikipedia.org/wiki/Chemical_stability?title=Stability stability] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn
[http://en.wikipedia.org/wiki/Activation_energy?title=ActivationEnergy activation energy], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from
[http://en.wikipedia.org/wiki/Ambient_temperature?title=Ambient ambient] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Isothermal_Titration_Calorimetry?title=ISC Isothermal Titration Calorimetry]
In an '''isothermal
[http://en.wikipedia.org/wiki/Titration?title=Titration titration] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point (
[http://en.wikipedia.org/wiki/Stoichiometry?title=Stoichiometry stoichiometry]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of
[http://en.wikipedia.org/wiki/Biochemistry?title=Biochemistry biochemistry], because it facilitates determination of substrate binding to
[http://en.wikipedia.org/wiki/Enzyme?title=Enzyme enzyme]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy Enthalpy]
*[http://en.wikipedia.org/wiki/Heat?title=Heat Heat]
*[http://en.wikipedia.org/wiki/Calorie?title=Calorie Calorie]
*[http://en.wikipedia.org/wiki/Heat_of_combustion?title=HeatOfCombustion Heat of combustion]
*[http://en.wikipedia.org/wiki/Calorimeter_constant?title=CalorimeterConstant Calorimeter constant]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
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[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
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[[th:แคลอรีมิเตอร์]]
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[[Category:Analytical]]

Calorimeter

2011-07-05T19:57:45Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in
[http://en.wikipedia.org/wiki/Polymer?title=Polymer polymer] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often
[http://en.wikipedia.org/wiki/Gold?title=Gold Gold], or Gold plated steel), and which will be able to withstand
[http://en.wikipedia.org/wiki/Pressure?title=Pressure pressure] (typically up to 100
[http://en.wikipedia.org/wiki/Bar_(unit)?title=Bar bar]). The presence of an
[http://en.wikipedia.org/wiki/Exothermic?title=Exothermic exothermic] event can then be used to assess the
[http://en.wikipedia.org/wiki/Chemical_stability?title=Stability stability] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn
[http://en.wikipedia.org/wiki/Activation_energy?title=ActivationEnergy activation energy], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from
[http://en.wikipedia.org/wiki/Ambient_temperature?title=Ambient ambient] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T17:55:56Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
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[[Category:Analytical]]

Calorimeter

2011-07-05T17:54:35Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
''Main article:''[http://en.wikipedia.org/wiki/Differential_scanning_calorimetry?title=DifferentialScanningCalorimetry Differential scanning calorimetry].

In a '''differential scanning calorimeter''' (DSC),
[http://en.wikipedia.org/wiki/Heat_flow?title=HeatFlow heat flow] into a sample—usually contained in a small
[http://en.wikipedia.org/wiki/Aluminium?title=Aluminium aluminium] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[http://en.wikipedia.org/wiki/Heat_flux?title=HeatFlux heat flux] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its
[http://en.wikipedia.org/wiki/Heat_capacity?title=HeatCapacity heat capacity] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a
[http://en.wikipedia.org/wiki/Thermocouple?title=Thermocouple thermocouple]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to
[http://en.wikipedia.org/wiki/Law_of_heat_conduction?title=NewtonLaw Newton's law of heat flow (20/11/2002)]) is analogous to, and much older than,
[http://en.wikipedia.org/wiki/Ohm%27s_law?title=Ohm Ohm's law] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the
[http://en.wikipedia.org/wiki/Integral?title=Integral integral] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T15:25:55Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called
[http://en.wikipedia.org/wiki/Joule_effect?title=JouleEffect Joule effect] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] of a reaction occurring in
[http://en.wikipedia.org/wiki/Solution?title=Solution solution] during which the
[http://en.wikipedia.org/wiki/Atmospheric_pressure?title=AtmosphericPressure atmospheric pressure] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested
[http://en.wikipedia.org/wiki/Styrofoam?title=Styrofoam Styrofoam] cups having holes through which a
[http://en.wikipedia.org/wiki/Thermometer?title=Thermometer thermometer] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides
[http://en.wikipedia.org/wiki/Thermal_insulation?title=Insulation insulation]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T15:10:35Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-0]</ref>
* HEL Phi-Tec<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-1]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://en.wikipedia.org/wiki/Calorimeter#cite_note-2 Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T15:07:02Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An
[http://en.wikipedia.org/wiki/Adiabatic_process?title=Adiabatic adiabatic] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://www.thermalhazardtechnology.com/products/ev-accelerating+rate+calorimeter THT EV-ARC]</ref>
* HEL Phi-Tec<ref>[http://www.helgroup.com/home/reactor-systems/safety.html?subpage=5 HEL Phi-Tec]</ref>
* A simple [http://en.wikipedia.org/wiki/Dewar_flask?title=DewarFlask Dewar flask]
* Systag FlexyTSC<ref>[http://www.systag.ch/E_400_TA.html Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

''Main article:''[http://en.wikipedia.org/wiki/Reaction_calorimeters?title=ReactionCalorimeters Reaction calorimeters].

A reaction calorimeter is a calorimeter in which a
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T14:45:58Z

Abouilly: Edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the
[http://en.wikipedia.org/wiki/Enthalpy?title=Enthalpy enthalpy] change per
[http://en.wikipedia.org/wiki/Mole_(unit)?title=Mole mole] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final
[http://en.wikipedia.org/wiki/Temperature?title=Temperature temperature]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and
[http://en.wikipedia.org/wiki/Specific_heat_capacity?title=SpeHeatCapacity specific heat capacities]
of the substances gives a value for the
[http://en.wikipedia.org/wiki/Energy?title=Energy energy] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An [[adiabatic process|adiabatic]] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://www.thermalhazardtechnology.com/products/ev-accelerating+rate+calorimeter THT EV-ARC]</ref>
* HEL Phi-Tec<ref>[http://www.helgroup.com/home/reactor-systems/safety.html?subpage=5 HEL Phi-Tec]</ref>
* A simple [[Dewar flask]]
* Systag FlexyTSC<ref>[http://www.systag.ch/E_400_TA.html Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

{{Main|Reaction calorimeters}}
A reaction calorimeter is a calorimeter in which a [[chemical reaction]] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T14:30:04Z

Abouilly: edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for
[http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the
[http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of
[http://en.wikipedia.org/wiki/Chemical_reaction?title=ChemicalReaction chemical reaction]s or
[http://en.wikipedia.org/wiki/Physical_change?title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the [[enthalpy]] change per [[Mole (unit)|mole]] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final [[temperature]]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and [[specific heat capacity|specific heat capacities]] of the substances gives a value for the [[energy]] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An [[adiabatic process|adiabatic]] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://www.thermalhazardtechnology.com/products/ev-accelerating+rate+calorimeter THT EV-ARC]</ref>
* HEL Phi-Tec<ref>[http://www.helgroup.com/home/reactor-systems/safety.html?subpage=5 HEL Phi-Tec]</ref>
* A simple [[Dewar flask]]
* Systag FlexyTSC<ref>[http://www.systag.ch/E_400_TA.html Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

{{Main|Reaction calorimeters}}
A reaction calorimeter is a calorimeter in which a [[chemical reaction]] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T14:19:50Z

Abouilly: edited article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry] thermochemistry.]]
A '''calorimeter''' (from [http://en.wikipedia.org/wiki/Latin?title=Latin Latin] ''calor'', meaning [http://en.wikipedia.org/wiki/Heat?title=heat heat]) is a device used for [http://en.wikipedia.org/wiki/Calorimetry?title=Calorimetry calorimetry], the [http://en.wikipedia.org/wiki/Science?title=Science science] of measuring the heat of [http://en.wikipedia.org/wiki/Chemical_reaction?
title=ChemicalReaction Chemical Reaction]s or [
http://en.wikipedia.org/wiki/Physical_change?
title=PhysicalChange physical change]s as well as [http://fr.wikipedia.org/w/index.php?
title=HeatCapacity heat capacity]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the [[enthalpy]] change per [[Mole (unit)|mole]] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final [[temperature]]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and [[specific heat capacity|specific heat capacities]] of the substances gives a value for the [[energy]] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An [[adiabatic process|adiabatic]] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://www.thermalhazardtechnology.com/products/ev-accelerating+rate+calorimeter THT EV-ARC]</ref>
* HEL Phi-Tec<ref>[http://www.helgroup.com/home/reactor-systems/safety.html?subpage=5 HEL Phi-Tec]</ref>
* A simple [[Dewar flask]]
* Systag FlexyTSC<ref>[http://www.systag.ch/E_400_TA.html Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

{{Main|Reaction calorimeters}}
A reaction calorimeter is a calorimeter in which a [[chemical reaction]] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
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[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T14:03:30Z

Abouilly: edit article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)?title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisier?title=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplace?title=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Heat?title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_change?title=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Black?title=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heat?title=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistry?title=Thermochemistry thermochemistry]thermochemistry.]]
A '''calorimeter''' (from [[Latin]] ''calor'', meaning [[heat]]) is a device used for [[calorimetry]], the [[science]] of measuring the heat of [[chemical reaction]]s or [[physical change]]s as well as [[heat capacity]]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the [[enthalpy]] change per [[Mole (unit)|mole]] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final [[temperature]]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and [[specific heat capacity|specific heat capacities]] of the substances gives a value for the [[energy]] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An [[adiabatic process|adiabatic]] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://www.thermalhazardtechnology.com/products/ev-accelerating+rate+calorimeter THT EV-ARC]</ref>
* HEL Phi-Tec<ref>[http://www.helgroup.com/home/reactor-systems/safety.html?subpage=5 HEL Phi-Tec]</ref>
* A simple [[Dewar flask]]
* Systag FlexyTSC<ref>[http://www.systag.ch/E_400_TA.html Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

{{Main|Reaction calorimeters}}
A reaction calorimeter is a calorimeter in which a [[chemical reaction]] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimeter?title=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-07-05T13:57:50Z

Abouilly: Added article.

''This article is about heat measuring devices. For particle detectors, see'' [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)title=Calorimeter Calorimeter (particle physics)]

[[Image:Ice-calorimeter.jpg|150px|right|thumb|The world’s first '''ice-calorimeter''', used in the winter of 1782-83, by [http://en.wikipedia.org/wiki/Antoine_Lavoisiertitle=AntoineLavoisier Antoine Lavoisier]
and [http://en.wikipedia.org/wiki/Pierre-Simon_Laplacetitle=PierreSimonLaplace Pierre-Simon Laplace]
, to determine the [http://en.wikipedia.org/wiki/Calorimeter_(particle_physics)title=heat heat] evolved in various [http://en.wikipedia.org/wiki/Chemical_changetitle=ChemicalChange chemical change(s)]
; calculations which were based on [http://en.wikipedia.org/wiki/Joseph_Blacktitle=JosephBlack Joseph Black] ’s prior discovery of [http://en.wikipedia.org/wiki/Latent_heattitle=LatentHeat latent heat]. These experiments mark the foundation of [http://en.wikipedia.org/wiki/Thermochemistrytitle=Thermochemistry thermochemistry]thermochemistry.]]
A '''calorimeter''' (from [[Latin]] ''calor'', meaning [[heat]]) is a device used for [[calorimetry]], the [[science]] of measuring the heat of [[chemical reaction]]s or [[physical change]]s as well as [[heat capacity]]. Differential scanning calorimeters, isothermal microcalorimeters, titration calorimeters and accelerated rate calorimeters are among the most common types. A simple calorimeter just consists of a thermometer attached to a metal container full of water suspended above a combustion chamber.

To find the [[enthalpy]] change per [[Mole (unit)|mole]] of a substance A in a reaction between two substances A and B, the substances are added to a calorimeter and the initial and final [[temperature]]s (before the reaction started and after it has finished) are noted. Multiplying the temperature change by the mass and [[specific heat capacity|specific heat capacities]] of the substances gives a value for the [[energy]] given off or absorbed during the reaction. Dividing the energy change by how many moles of A were present gives its enthalpy change of reaction. This method is used primarily in academic teaching as it describes the theory of calorimetry. It does not account for the heat loss through the container or the heat capacity of the thermometer and container itself. In addition, the object placed inside the calorimeter show that the objects transferred their heat to the calorimeter and into the liquid, and the heat absorbed by the calorimeter and the liquid is equal to the heat given off by the metals.

==Adiabatic calorimeters==
An [[adiabatic process|adiabatic]] calorimeter is a calorimeter used to examine a runaway reaction. Since the calorimeter runs in an adiabatic environment, any heat generated by the material sample under test causes the sample to increase in temperature, thus fuelling the reaction. 
No adiabatic calorimeter is truly adiabatic - some heat will be lost by the sample to the sample holder. Examples of adiabatic calorimeters are:-
* THT EV-Accelerating Rate Calorimeter<ref>[http://www.thermalhazardtechnology.com/products/ev-accelerating+rate+calorimeter THT EV-ARC]</ref>
* HEL Phi-Tec<ref>[http://www.helgroup.com/home/reactor-systems/safety.html?subpage=5 HEL Phi-Tec]</ref>
* A simple [[Dewar flask]]
* Systag FlexyTSC<ref>[http://www.systag.ch/E_400_TA.html Systag FlexyTSC]</ref> a successor of their SIKAREX unit - the electronics of which could be used to apply a feedback system to heat the sample holder to give a result closer to true adiabaticy, however as the sample holder is an open ended glass tube, one soon loses the sample as a great deal of smoke.

==Reaction calorimeters==

{{Main|Reaction calorimeters}}
A reaction calorimeter is a calorimeter in which a [[chemical reaction]] is initiated within a closed insulated container. Reaction heats are measured and the total heat is obtained by integrating heatflow versus time. This is the standard used in industry to measure heats since industrial processes are engineered to run at constant temperatures. Reaction calorimetry can also be used to determine maximum heat release rate for chemical process engineering and for tracking the global kinetics of reactions. There are four main methods for measuring the heat in reaction calorimeter:

===Heat flow calorimetry===

The cooling/heating jacket controls either the temperature of the process or the temperature of the jacket. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid. In addition fill volumes (i.e. wetted area), specific heat, heat transfer coefficient have to be determined to arrive at a correct value. It is possible with this type of calorimeter to do reactions at reflux, although the accuracy is not as good.

===Heat balance calorimetry===

The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the heat gained or lost by the heat transfer fluid.

===Power compensation===
Power compensation uses a heater placed within the vessel to maintain a constant temperature. The energy supplied to this heater can be varied as reactions require and the calorimetry signal is purely derived from this electrical power.

===Constant flux===
Constant flux calorimetry (or COFLUX as it is often termed) is derived from heat balance calorimetry and uses specialized control mechanisms to maintain a constant heat flow (or flux) across the vessel wall.

==Bomb calorimeters==

[[File:Bombenkalorimeter mit bombe.jpg|thumb|Bomb calorimeter]]

A bomb calorimeter is a type of constant-volume calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure within the calorimeter as the reaction is being measured. Electrical energy is used to ignite the fuel; as the fuel is burning, it will heat up the surrounding air, which expands and escapes through a tube that leads the air out of the calorimeter. When the air is escaping through the copper tube it will also heat up the water outside the tube. The temperature of the water allows for calculating calorie content of the fuel.

In more recent calorimeter designs, the whole bomb, pressurized with excess pure oxygen (typically at 30atm) and containing a known mass of sample (typically 1-1.5 g) and a small fixed amount of water (to absorb produced acid gases), is submerged under a known volume of water (ca. 2000 ml) before the charge is (again electrically) ignited. The bomb, with sample and oxygen, form a closed system - no air escapes during the reaction. The energy released by the combustion raises the temperature of the steel bomb, its contents, and the surrounding water jacket. The temperature change in the water is then accurately measured. This temperature rise, along with a bomb factor (which is dependent on the heat capacity of the metal bomb parts) is used to calculate the energy given out by the sample burn. A small correction is made to account for the electrical energy input, the burning fuse, and acid production (by titration of the residual liquid). After the temperature rise has been measured, the excess pressure in the bomb is released.

Basically, a bomb calorimeter consists of a small cup to contain the sample, oxygen, a stainless steel bomb, water, a stirrer, a thermometer, the dewar (to prevent heat flow from the calorimeter to the surroundings) and ignition circuit connected to the bomb.

Since there is no heat exchange between the calorimeter and surroundings → Q = 0 (adiabatic) ; no work performed → W = 0
Thus, the total internal energy change ΔU(total) = Q + W = 0

Also, total internal energy change ΔU(total) = ΔU(system) + ΔU(surroundings) = 0
→ ΔU(system) = - ΔU(surroundings) = -Cv ΔT (constant volume → dV = 0)

where Cv = heat capacity of the bomb

Before the bomb can be used to determine heat of combustion of any compound, it must be calibrated.
The value of Cv can be estimated by
Cv (calorimeter) = m (water). Cv (water) + m (steel). Cv (steel)

m (water) and m (steel) can be measured;

Cv(water)= 1 cal/g.K

Cv(steel)= 0.1 cal/g.K

In laboratory, Cv is determined by running a compound with known heat of combustion value: Cv = Hc/ΔT

Common compounds are benzoic acid (Hc = 6318 cal/g) or p-methyl benzoic acid (Hc = 6957 cal/g).

Temperature (T) is recorded every minute and ΔT = T(final) - T(initial)

A small factor contributes to the correction of the total heat of combustion is the fuse wire. Nickel fuse wire is often used and has heat of combustion = 981.3 cal/g

In order to calibrate the bomb, a small amount (~ 1 g) of benzoic acid, or p-methyl benzoic acid is weighed.
A length of Nickel fuse wire (~10 cm) is weighed both before and after the combustion process. Mass of fuse wire burned Δm = m(before) - m(after)

The combustion of sample (benzoic acid) inside the bomb ΔHc = ΔHc (benzoic acid) x m (benzoic aicd) + ΔHc (Ni fuse wire) x Δm (Ni fuse wire)

ΔHc = Cv. ΔT → Cv = ΔHc/ΔT

Once Cv value of the bomb is determined, the bomb is ready to use to calculate heat of combustion of any compounds by ΔHc = Cv. ΔT

<ref>Polik, W. (1997). Bomb Calorimetery. Retrieved from http://www.chem. hope. edu/ ~polik/Chem345-1997/calorimetry/bombcalorimetry1.html</ref>
<ref>Bozzelli, J. (2010). Heat of Combustion via Calorimetry: Detailed Procedures. Chem 339-Physical Chemistry Lab for Chemical Engineers –Lab Manual.</ref>

==Calvet-type calorimeters==
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94 % +/- 1 % of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.

The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called [[Joule effect]] or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials.
The main advantages of this type of calibration are as follows:
*It is an absolute calibration.
*The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
*It can be applied to any experimental vessel volume.
*It is a very accurate calibration.

An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).<ref name="Calvet-type calorimeter">[http://www.setaram.com/C80.htm C80 Calorimeter from Setaram Instrumentation]</ref>

==Constant-pressure calorimeter==

A '''constant-pressure calorimeter''' measures the change in [[enthalpy]] of a reaction occurring in [[solution]] during which the [[atmospheric pressure]] remains constant.

An example is a coffee-cup calorimeter, which is constructed from two nested [[Styrofoam]] cups having holes through which a [[thermometer]] and a stirring rod can be inserted. The inner cup holds the solution in which of the reaction occurs, and the outer cup provides [[Thermal insulation|insulation]]. Then

<math>Cp = \frac {W\Delta H}{M\Delta T}</math>

where

:<math>Cp</math> = Specific heat at constant pressure
:<math>\Delta H</math> = Enthalpy of solution
:<math>\Delta T</math> = Change in temperature
:<math>W</math> = mass of solute
:<math>M</math> = molecular mass of solute

==Differential scanning calorimeter==
{{main|Differential scanning calorimetry}}
In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminium]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.

In a '''[[heat flux]] DSC''', both pans sit on a small slab of material with a known (calibrated) heat resistance K. The temperature of the calorimeter is raised linearly with time (scanned), i.e., the heating rate
dT/dt = β
is kept constant. This time linearity requires good design and good (computerized) temperature control. Of course, controlled cooling and isothermal experiments are also possible.

Heat flows into the two pans by conduction. The flow of heat into the sample is larger because of its [[heat capacity]] ''Cp''. The difference in flow ''dq''/''dt'' induces a small temperature difference Δ''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:

<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>

Note that this formula (equivalent to [[Law of heat conduction|Newton's law of heat flow]]) is analogous to, and much older than, [[Ohm's law]] of electric flow:
ΔV = R dQ/dt = R I.

When suddenly heat is absorbed by the sample (e.g., when the sample melts), the signal will respond and exhibit a peak.

<math>{dq\over dt} = C_p \beta + f(t,T) </math>

From the [[integral]] of this peak the enthalpy of melting can be determined, and from its onset the melting temperature.

Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.

A '''modulated temperature differential scanning calorimeter''' (MTDSC) is a type of DSC in which a small oscillation is imposed upon the otherwise linear heating rate.

This has a number of advantages. It facilitates the direct measurement of the heat capacity in one measurement, even in (quasi-)isothermal conditions. It permits the simultaneous measurement of heat effects that are reversible and not reversible at the timescale of the oscillation (reversing and non-reversing heat flow, respectively). It increases the sensitivity of the heat capacity measurement, allowing for scans at a slow underlying heating rate.

'''Safety Screening''':- DSC may also be used as an initial safety screening tool. In this mode the sample will be housed in a non-reactive crucible (often [[Gold]], or Gold plated steel), and which will be able to withstand [[pressure]] (typically up to 100 [[bar (unit)|bar]]). The presence of an [[exothermic]] event can then be used to assess the [[chemical stability|stability]] of a substance to heat. However, due to a combination of relatively poor sensitivity, slower than normal scan rates (typically 2-3°/min - due to much heavier crucible) and unknonwn [[activation energy]], it is necessary to deduct about 75-100°C from the initial start of the observed exotherm to '''suggest''' a maximum temperature for the material. A much more accurate data set can be obtained from an adiabatic calorimeter, but such a test may take 2–3 days from [[ambient temperature|ambient]] at a rate of 3°C increment per half hour.

==Isothermal titration calorimeter==
{{main|Isothermal Titration Calorimetry}}
In an '''isothermal [[titration]] calorimeter''', the heat of reaction is used to follow a titration experiment. This permits determination of the mid point ([[stoichiometry]]) (N) of a reaction as well as its enthalpy (delta H), entropy (delta S) and of primary concern the binding affinity (Ka)

The technique is gaining in importance particularly in the field of [[biochemistry]], because it facilitates determination of substrate binding to [[enzyme]]s. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

==See also==
{{commons category|Calorimeters}}
*[[Enthalpy]]
*[[Heat]]
*[[Calorie]]
*[[Heat of combustion]]
*[[Calorimeter constant]]

==References==
[http://en.wikipedia.org/wiki/Calorimetertitle=WikipediaCalorimeter Wikipedia]

{{Laboratory equipment}}

[[Category:Measuring instruments]]
[[Category:Laboratory equipment]]

[[ar:مسعر]]
[[be-x-old:Калярымэтры]]
[[bg:Калориметър]]
[[ca:Calorímetre]]
[[cs:Kalorimetr]]
[[da:Kalorimeter]]
[[de:Kalorimeter]]
[[es:Calorímetro]]
[[fr:Calorimètre]]
[[hi:कैलोरीमीटर]]
[[io:Kalorimetro]]
[[id:Kalorimeter]]
[[it:Calorimetro]]
[[he:קלורימטר]]
[[ht:Kalorimèt]]
[[nl:Calorimeter]]
[[ja:熱#熱量計]]
[[pl:Kalorymetr]]
[[pt:Calorímetro]]
[[ru:Калориметр]]
[[simple:Calorimeter]]
[[sk:Kalorimeter]]
[[sl:Kalorimeter]]
[[sr:Kalorimetar]]
[[fi:Kalorimetri]]
[[sv:Kalorimeter]]
[[th:แคลอรีมิเตอร์]]
[[tr:Kalorimetre]]
[[uk:Калориметр]]

[[Category:Analytical]]

Calorimeter

2011-06-30T20:49:09Z

Abouilly: Deleted informations.

A calorimeter measures heat, primarily of chemical reactions.
[[Category:Analytical]]

Calorimeter

2011-06-29T21:22:19Z

Abouilly:

A calorimeter measures heat, primarily of chemical reactions.
[[Category:Analytical]]

== GE Healthcare ==

MicroCalorimetry VP Differential Scanning Calorimeter
[http://www.labwrench.com/?equipment.view/equipmentNo/10296/MicroCalorimetry--GE-Healthcare-/VP-Differential-Scanning-Calorimeter/]

MicroCalorimetry VP-Isothermal Titration Calorimeter
[http://www.labwrench.com/?equipment.view/equipmentNo/10300/MicroCalorimetry--GE-Healthcare-/VP-Isothermal-Titration-Calorimeter/]

== HEL ==

BTC
[http://www.labwrench.com/?equipment.view/equipmentNo/1839/HEL/BTC/]

Phi-TEC I
[http://www.labwrench.com/?equipment.view/equipmentNo/1836/HEL/Phi-TEC-I/]

Phi-TEC II
[http://www.labwrench.com/?equipment.view/equipmentNo/1837/HEL/Phi-TEC-II/]

Simular
[http://www.labwrench.com/?equipment.view/equipmentNo/1835/HEL/Simular/]

TSu
[http://www.labwrench.com/?equipment.view/equipmentNo/1838/HEL/TSu/]

== IKA ==

C 200
[http://www.labwrench.com/?equipment.view/equipmentNo/5053/IKA/C-200/]

C 2000 Basic
[http://www.labwrench.com/?equipment.view/equipmentNo/5054/IKA/C-2000-Basic/]

C 2000 Control
[http://www.labwrench.com/?equipment.view/equipmentNo/5068/IKA/C-2000-Control-/]

C 5000 control package 2/12
[http://www.labwrench.com/?equipment.view/equipmentNo/5077/IKA/C-5000-control-package-2-12/]

C 5000 control package 2/10
[http://www.labwrench.com/?equipment.view/equipmentNo/5076/IKA/C-5000-control-package-2-10/]

C 5000 control package 1/12
[http://www.labwrench.com/?equipment.view/equipmentNo/5075/IKA/C-5000-control-package-1-12/]

C 5000 control package 1/10
[http://www.labwrench.com/?equipment.view/equipmentNo/5074/IKA/C-5000-control-package-1-10/]

C 7000 basic equipment set 1 and 2
[http://www.labwrench.com/?equipment.view/equipmentNo/5079/IKA/C-7000-basic-equipment-set-1-and-2/]

== LECO Corporation ==

AC500
[http://www.labwrench.com/?equipment.view/equipmentNo/7478/LECO-Corporation/AC500/]

AC600
[http://www.labwrench.com/?equipment.view/equipmentNo/1525/LECO-Corporation/AC600/]

== Mettler Toledo ==

HP DSC 1
[http://www.labwrench.com/?equipment.view/equipmentNo/7470/Mettler-Toledo/HP-DSC-1/]

RC1 Workstations
[http://www.labwrench.com/?equipment.view/equipmentNo/6792/Mettler-Toledo/RC1-Workstations/]

Toledo DSC 1
[http://www.labwrench.com/?equipment.view/equipmentNo/7469/Mettler-Toledo/DSC-1/]

== Netzch ==

Accelerating Rate Calorimeter 244 (ARC®)
[http://www.labwrench.com/?equipment.view/equipmentNo/7462/Netzsch/Accelerating-Rate-Calorimeter-244--ARC--/]

Accelerating Rate Calorimeter 254 (ARC®)
[http://www.labwrench.com/?equipment.view/equipmentNo/7463/Netzsch/Accelerating-Rate-Calorimeter-254--ARC--/]

MMC 274 Nexus®
[http://www.labwrench.com/?equipment.view/equipmentNo/7464/Netzsch/MMC-274-Nexus-/]

== Parr Instrument ==

Model 1341
[http://www.labwrench.com/?equipment.view/equipmentNo/5027/Parr-Instruments/Model-1341/]

Model 6100
[http://www.labwrench.com/?equipment.view/equipmentNo/5026/Parr-Instruments/Model-6100/]

Model 6200
[http://www.labwrench.com/?equipment.view/equipmentNo/5021/Parr-Instruments/Model-6200/]

Model 6300
[http://www.labwrench.com/?equipment.view/equipmentNo/5018/Parr-Instruments/Model-6300/]

Model 6400
[http://www.labwrench.com/?equipment.view/equipmentNo/5017/Parr-Instruments/Model-6400/]

Model 6725
[http://www.labwrench.com/?equipment.view/equipmentNo/5028/Parr-Instruments/Model-6725/]

Model 6750
[http://www.labwrench.com/?equipment.view/equipmentNo/5043/Parr-Instruments/Model-6750/]

Model 6755
[http://www.labwrench.com/?equipment.view/equipmentNo/5035/Parr-Instruments/Model-6755/]

Parr Detonation Calorimeter
[http://www.labwrench.com/?equipment.view/equipmentNo/5048/Parr-Instruments/Parr-Detonation-Calorimeter/]

== TA Instrument ==

Discovery DSC
[http://www.labwrench.com/?equipment.view/equipmentNo/8126/TA-Instruments/Discovery-DSC/]

Q2000
[http://www.labwrench.com/?equipment.view/equipmentNo/8127/TA-Instruments/Q2000/]

== Thermo Scientific ==

Flo-Cal*
[http://www.labwrench.com/?equipment.view/equipmentNo/8122/Thermo-Scientific/Flo-Cal-/]

Tissue Grinder

2011-06-29T20:05:53Z

Abouilly: Added definition.

The tissue grinder is used for homogenizing delicate tissues (such as intestines, liver, and heart) and cells. (www.biocompare.com)
[[Category:Basic Laboratory]]

Overhead Stirrer

2011-06-29T19:36:28Z

Abouilly: Added definition.

Overhead Stirrers, not to be confused with magnetic stirrers, are used for standard mixing of the higher viscosity substances. (Wikipedia)
[[Category:Stirrer]]

Mixer

2011-06-29T19:05:17Z

Abouilly: Added definition.

A vortex mixer is a simple device used commonly in laboratories to mix small vials of liquid. (Wikipedia)
[[Category:Basic Laboratory]]

CO2 Incubator

2011-06-29T18:59:54Z

Abouilly: Changed definition.

Although cultures can be incubated in sealed flasks in a regular dry incubator or a hot room, some vessels, e.g., Petri dishes or multiwell plates, require a controlled atmosphere with high humidity and elevated CO2 tension. The cheapest way of controlling the gas phase is to place the cultures in a plastic box, or chamber (Bellco, MP Biomedicals): Gas the container with the correct CO2 mixture and then seal it. (Wikipedia)
[[Category:Lab Incubator]]

General Purpose Incubator

2011-06-29T18:58:18Z

Abouilly: Added definition.

In biology, an incubator is a device used to grow and maintain microbiological cultures or cell cultures. The incubator maintains optimal temperature, humidity and other conditions such as the carbon dioxide (CO2) and oxygen content of the atmosphere inside. (Wikipedia)
[[Category:Lab Incubator]]

Basic Laboratory

2011-06-29T18:33:52Z

Abouilly: Added definitions.

A laboratory (pronounced /ləˈbɒrətəri, ˈlæbərətri/; informally, lab) is a facility that provides controlled conditions in which scientific research, experiments, and measurement may be performed. (Wikipedia)
[[Category:Basic Laboratory]]

Data System

2011-06-29T18:31:47Z

Abouilly: Added definitions.

The means, either manual or automatic, of converting data into action or decision information, including the forms, procedures, and processes which together provide an organized and interrelated means of recording, communicating, processing, and presenting information relative to a definable function or activity. (www.answers.com)
[[Category:Analytical]]
[[Category:System]]

ELN-Electronic Laboratory Notebook

2011-06-29T18:20:58Z

Abouilly: Added article.

An electronic laboratory notebook is a software program designed to replace paper laboratory notebooks. Lab notebooks in general are used by scientists and technicians to document research, experiments and procedures performed in a laboratory. (Wikipedia)
[[Category:Analytical]]

Ion Chromatography

2011-06-29T18:10:10Z

Abouilly: Changed a link to category.

Ion-exchange chromatography (or ion chromatography) is a process that allows the separation of ions and polar molecules based on their charge. (Wikipedia)
[[Category:Chromatography]]
[[Category:HPLC - High Performance Liquid Chromatography]]

GPC Gel Permeation Chromatography

2011-06-29T18:08:55Z

Abouilly: Changed a link to category.

Gel permeation chromatography (GPC) is a type of size exclusion chromatography (SEC), that separates analytes on the basis of size. (Wikipedia)
[[Category:Chromatography]]
[[Category:HPLC - High Performance Liquid Chromatography]]

FPLC – Fast Protein Liquid Chromatography

2011-06-29T18:07:22Z

Abouilly: Changed a link to category.

Fast protein liquid chromatography (FPLC), is a form of liquid chromatography similar to high-performance liquid chromatography that is used to separate or purify proteins and other polymers from complex mixtures. FPLC system is a complete system for laboratory scale chromatographic separations of proteins and other biomolecules. (Wikipedia)
[[Category:Chromatography]]
[[Category:HPLC - High Performance Liquid Chromatography]]

HPLC - High Performance Liquid Chromatography

2011-06-29T18:06:33Z

Abouilly: Changed a link to category.

High-performance liquid chromatography (sometimes referred to as high-pressure liquid chromatography), HPLC, is a chromatographic technique that can separate a mixture of compounds and is used in biochemistry and analytical chemistry to identify, quantify and purify the individual components of the mixture. (Wikipedia)
[[Category:Chromatography]]
[[Category:HPLC - High Performance Liquid Chromatography]]

GC - Gas Chromatography

2011-06-29T18:05:44Z

Abouilly: Changed a link to category.

Gas chromatography (GC), is a common type of chromatography used in analytic chemistry for separating and analysing compounds that can be vaporized without decomposition. (Wikipedia)
[[Category:Chromatography]]
[[Category:GC - Gas Chromatography]]

Category:Chromatography

2011-06-29T18:04:39Z

Abouilly: Added category.

{{cat main|Chromatography}}
This category is designated for articles about [[chromatography]] generally, and specific chromatography products vendors offer.

TOF-MS System

2011-06-29T18:03:18Z

Abouilly: Changed a link to category.

[[Category:Mass Spectrometer]]
[[Category:System]]

Tandem MS System

2011-06-29T18:02:35Z

Abouilly: Changed a link to category.

[[Category:Mass Spectrometer]]
[[Category:System]]

GC-MS System

2011-06-29T18:01:56Z

Abouilly: Added article.

[[Category:Mass Spectrometer]]
[[Category:System]]

CE-MS System

2011-06-29T18:00:13Z

Abouilly: Corrected name of category.

[[Category:Mass Spectrometer]]
[[Category:System]]

CE-MS System

2011-06-29T17:59:59Z

Abouilly: Changed a link to category.

[[Category:Mass Spectrometer]]
[[Category:CE - MS System]]

ICP System

2011-06-29T17:58:58Z

Abouilly: Changed a link to category.

[[Category:Spectroscopy]]
[[Category:System]]

UHPLC System

2011-06-29T17:57:26Z

Abouilly: Changed a link to category.

[[Category:HPLC - High Performance Liquid Chromatography]]
[[Category:System]]

Chromatography Data Systems (HPLC)

2011-06-29T17:56:52Z

Abouilly: Changed a link to category.

[[Category:Chromatography Data Systems (HPLC)]]
[[Category:HPLC - High Performance Liquid Chromatography]]
[[Category:System]]

GC System

2011-06-29T17:53:41Z

Abouilly: Changed a link to category.

[[Category:GC - Gas Chromatography]]
[[Category:System]]

Chromatography Data Systems (GC)

2011-06-29T17:53:02Z

Abouilly: Changed a link to category.

A chromatography software, also known as a Chromatography data system (CDS), collects and analyzes chromatographic results delivered by chromatography detectors. (Wikipedia)
[[Category:Chromatography Data Systems (GC)]]
[[Category:GC - Gas Chromatography]]
[[Category:System]]

Immunoassay System

2011-06-29T17:52:24Z

Abouilly: Changed a link to category.

An immunoassay is a biochemical test that measures the presence or concentration of a substance in solutions that frequently contain a complex mixture of substances. (Wikipedia)
[[Category:Biotechnology]]
[[Category:System]]

Imaging System

2011-06-29T17:51:50Z

Abouilly: Changed a link to category.

Imaging is the representation or reproduction of an object's outward form; especially a visual representation (i.e., the formation of an image). (Wikipedia)
[[Category:Biotechnology]]
[[Category:System]]

Data System

2011-06-29T17:50:27Z

Abouilly: Changed a link to category.

[[Category:Analytical]]
[[Category:System]]

Category:System

2011-06-29T17:49:30Z

Abouilly: Added category.

{{cat main|System}}
This category is designated for articles about [[System|systems]] generally, and specific systems products vendors offer.

Refrigerated Incubator

2011-06-29T15:30:20Z

Abouilly: Added definitions.

A refrigerated incubator is designed to maintain a constant temperature based on cooling requirements for research. Typical temperature settings range from -50°C to 65°C based upon varying convection types, though forced air circulation is most commonly used. (www.labcompare.com)
[[Category:Lab Incubator]]

Hybridization Oven

2011-06-29T15:07:52Z

Abouilly: Added definitions.

Hybridization incubators, also known as hybridization ovens, provide defined temperature control, agitation, and consistency throughout the incubator chamber. (www.labcompare.com)
[[Category:Lab Incubator]]

Peptide Synthesizer

2011-06-29T14:51:48Z

Abouilly: Changed a link to category.

[[Category:Biotechnology]]
[[Category:Synthesizer]]