Difference between revisions of "Calorimeter" - New World Encyclopedia

Latest revision as of 14:44, 27 March 2013

The world’s first ice-calorimeter. Antoine Lavoisier and Pierre-Simon Laplace used it in the winter of 1782-83, to determine the heat produced during various chemical changes. These experiments marked the founding of the field of thermochemistry.

A calorimeter is an instrument used for measuring the quantity of heat absorbed or released by matter when it undergoes a chemical reaction or physical change. Historically, such precision measurements have helped open a window onto the molecular and atomic structure of matter because the movement of molecules and atoms in matter collectively carries a quantity of heat energy that is distinctive for each type of matter and its chemical reactions. Based on such calorimetric measurements, scientists have developed tables giving the heat capacities of substances. Data produced by calorimeters has been foundational to the development of such technologies as steam boilers, turbines, rocket engines, internal combustion engines, oil refineries, and plastic product factories.

A widely accepted standard reference material used in many calorimeters is water because it has a high and precisely measured heat capacity, is easy to work with, and is readily available. A simple type of calorimeter would consist of an insulated container of water with a thermometer fixed in the water. To measure the heat capacity of molten lead, for example, an investigator could place a bowl of molten lead inside the calorimeter and record the temperature drop of the cooling lead and the corresponding temperature rise of the water. Knowing the mass of both the water and the lead, the investigator would have enough information to calculate lead's heat capacity.

Calorimeters come in many different types, some targeted to measuring the heat capacity of new materials (differential scanning calorimeters), while others measure such diverse aspects as the heat generated by new or untested reactions (isothermal microcalorimeters), heat of combustion and burn rates (accelerated rate calorimeters), and the energy of elementary particles (electromagnetic and hadronic calorimeters).

The word "calorimeter" is derived from the Latin word calor, meaning heat. The method or process of carrying out such measurements is called calorimetry.

Representative calculations

Calculating the heat capacity of molten lead based on data collected in the example above requires using the formula

Q = smΔT

where Q is the quantity of heat, s is the specific heat(the material's heat capacity divided by the heat capacity of water), m is the mass of the material, and ΔT is the temperature change. Inside the calorimeter, the heat lost by the lead(Q_l) is, to the first approximation, equal to the heat gained by the water(Q_w]). In this case, (smΔT)_l must be equal to (smΔT)_w. Since the only unknown quantity here is s_l, it can be calculated according to the formula

s_l = (smΔT)_w/(mΔT)_l

To gain more insight about the complex energy dynamics operative in even the most inert and quiet looking piece of matter, scientists apply calorimetric measurements to the subtle concept of enthalpy, a measure of the internal energy of a system at constant pressure. For each substance, its internal energy content (U) as embodied in the movements of its molecular and atomic level components is distinctively dependent not only on the temperature (T) but on the pressure (P) and volume (V).

Enthalpy (H) is defined as H = U + PV. In words, enthalpy change (ΔH) is the amount of heat released or absorbed when a chemical reaction occurs at constant pressure. (Standardized enthalpy measurements are often expressed in terms of 1 mole of a substance X, which is a quantity of X equal to the molecular weight of X expressed in grams.) To find the enthalpy change per mole of a liquid substance X, for example, in reaction with liquid Y, the two liquids are mixed inside the calorimeter and the initial and final (after the reaction has finished) temperatures are noted. Working with the basic formula, Q = smΔT and multiplying the temperature change times the masses and the specific heat capacities of the two liquids permits a further calculation that yields a value for the energy given off during the reaction (assuming the reaction was exothermic). Dividing the energy change by the number of moles of X present gives its enthalpy change of reaction. This method is used primarily in academic teaching, as it describes the theory of calorimetry. It doesn’t, however, account for heat loss through the container or the heat capacity of the thermometer and container itself.

Types

Reaction calorimeters

An example of a Reaction calorimeter

A Reaction calorimeter measures the heat energy released or absorbed during a reaction that occurs inside the calorimeter. This is the standard instrument used for measuring heats of industrial processes. Reaction calorimetry can also be used for determining the maximum rate of heat release in chemical process engineering.

Bomb calorimeters

A bomb calorimeter is a type of reaction calorimeter used for measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand strong pressure and force as the reaction is being measured. Electrical energy is used to ignite the fuel. As the fuel burns, it heats up the surrounding air, which expands and escapes through a copper tube passing through water on the way out of the calorimeter. The temperature change of the water heated by the air escaping through the copper tube provides the measurement needed to calculate the energy content of the fuel.

In more recent calorimeter designs the whole bomb, pressurized with excess pure oxygen (typically around 30 atm) and containing a known mass of fuel, is submerged under a known volume of water before the charge is (again, electrically) ignited. 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 burning fuel. A small correction is made to account for the electrical energy input and the burning fuse.

Differential scanning calorimeter

In a differential scanning calorimeter (DSC), heat flow into a sample—usually contained in a small aluminum capsule or "pan"—is measured differentially; that is, 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 heat resistance. The temperature of the calorimeter is raised at a constant heating rate, an objective that requires good design and good (computerized) temperature control. A heat flux DSC can also be used for experiments requiring controlled cooling or constant temperature.

During the experiments, heat flows into the two pans by conduction, with the flow of heat into the sample being larger because of the sample's larger heat capacity. The difference in the heat flow into the two pans induces a small temperature difference across the slab. This temperature difference is measured using a thermocouple. The heat capacity can in principle be determined from this signal. Differential scanning calorimetry is a workhorse technique in many fields, particularly in polymer characterization.

Isothermal titration calorimeter

In an isothermal titration calorimeter, the heat of reaction is used to follow a titration experiment, one in which the concentration of an unknown reagent is determined by using a standard concentration of another reagent that chemically reacts with the unknown. This permits determination of the mid point of a reaction as well as other key parameters. The technique is gaining importance, particularly in the field of biochemistry, because it facilitates determination of substrate binding to enzymes. The technique is commonly used in the pharmaceutical industry to characterize potential drug candidates.

X-ray microcalorimeter

X ray microcalorimeter diagram

In 1982, a new approach to non-dispersive X-ray spectroscopy, based on the measurement of heat rather than charge, was proposed by Moseley et al. (1984). The detector, which is the basis of the X-ray microcalorimeter, works by sensing the heat pulses generated by X-ray photons when they are absorbed into a material as heat energy. The temperature increase is directly proportional to photon energy. This invention combines high detector efficiency with high energy resolution, mainly achievable because it is operated at a low temperature.

These cryogenic microcalorimeters have a thermometer to measure the change in temperature of a low-heat-capacity mass that can in principle absorb incident photons not only in the X-ray range, but also in the ultraviolet, visible, or near infrared ranges. This mass is connected by a weak link to a low-temperature heat sink, which provides the thermal isolation needed for a temperature rise to occur. Building on the original innovative approach, a large development effort is still expanding the field of cryogenic microcalorimetry. The first astronomical spacecraft carrying cryogenic microcalorimeters was the orbiting x-ray observatory Suzaku/Astro-E2launched in July 2005. NASA as well as ESA have plans for future missions (Constellation-X and XEUS, respectively) that will use some sort of micro-calorimeters.

High-energy particle calorimeter

In particle physics, a calorimeter is a component of a detector that measures the energy of entering particles.

Calorimetry

As scientists have developed and worked with calorimeters, the new field of calorimetry has developed in parallel with the mission of measuring the quantity of heat absorbed or released when matter undergoes a change in its physical, chemical, or electrical state. As a field of study in its own right, calorimetry overviews the whole history and range of calorimeters and provides a useful way of looking at their different types.

"Indirect calorimetry" calculates the heat generated by living organisms when their metabolic processes yield waste carbon dioxide and nitrogen. Lavoisier noted in 1780 that heat production can be predicted from oxygen consumption by living organisms. The Dynamic Energy Budget theory explains why this procedure is valid. Of course, heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.

Constant-volume

Constant-volume calorimetry using a constant-volume calorimeter, constrains the test system to perform no work, so the heat gain or loss measured equals the change in internal energy of the system. The equation for constant-volume calorimetry is:

q=C_{V}\Delta t=\Delta U\,

where

ΔU = change in internal energy

C_V = heat capacity of the system of volume V

Since in constant-volume calorimetry the pressure is not kept constant, the heat measured does not represent the enthalpy change.

Constant-pressure

Constant-pressure calorimetry uses a constant-pressure calorimeter measures a quantity of heat energy exchange equal to the change in internal energy of the system minus the work (w) performed:

q=\Delta U-w\,

Since in constant-pressure calorimetry, pressure is kept constant, the heat measured represents the enthalpy change:

q=\Delta H=H_{\mathrm {final} }-H_{\mathrm {initial} }\,

Notes

References
ISBN links support NWE through referral fees

Larijani,Bananshé, Colin A. Rosser, and Rudiger Woscholski, ed. 2006. Chemical Biology: Techniques and Applications. West Sussex, England: John Wiley and Sons, Ltd. ISBN-13 978-0-470-09064-0
Beezer, A.E., ed. 1980. Biological Microcalorimetry. New York: Academic Press, Inc. ISBN 0-12-083550-9

Besancon, Robert M., ed. 1985. The Encyclopedia of Physics, 3rd ed. New York: Van Nostrand Reinhold Company. ISBN 0-442-25778-3

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@@ Line 1: / Line 1: @@
-{{Claimed}}
+{{Images OK}}{{Submitted}}{{Approved}}{{Paid}}{{copyedited}}
-[[Image:Ice-calorimeter.jpg|250px|right|thumb|The world’s first '''ice-calorimeter'''. [[Antoine Lavoisier]] and [[Pierre-Simon Laplace]] used it in the winter of 1782-83, to determine the [[heat]] produced during various [[chemical change]]s. These experiments marked the founding of the field of [[thermochemistry]].]]
+[[Image:Ice-calorimeter.jpg|250px|right|thumb|The world’s first '''ice-calorimeter.''' [[Antoine Lavoisier]] and [[Pierre-Simon Laplace]] used it in the winter of 1782-83, to determine the [[heat]] produced during various [[chemical change]]s. These experiments marked the founding of the field of [[thermochemistry]].]]
-A '''calorimeter''' is an instrument used for measuring the quantity of heat absorbed or released by matter when it undergoes a [[chemical reaction]] or [[physical change]]. Historically such precision measurements have helped open a window onto the molecular and atomic structure of matter because the movement of molecules and atoms in matter collectively carries a quantity of heat energy that is distinctive for each type of matter and its chemical reactions. Based on such calorimetric measurements, scientists have developed tables giving the [[heat capacity|heat capacities]] of [[substance]]s, which knowledge, in turn, has been foundational for the development of diverse technologies. These range from steam boilers and turbines to rocket engines, internal combustion engines, oil refineries, and plastic product factories.
+A '''calorimeter''' is an instrument used for measuring the quantity of heat absorbed or released by matter when it undergoes a [[chemical reaction]] or [[physical change]]. Historically, such precision measurements have helped open a window onto the molecular and atomic structure of matter because the movement of molecules and atoms in matter collectively carries a quantity of heat energy that is distinctive for each type of matter and its chemical reactions. Based on such calorimetric measurements, scientists have developed tables giving the [[heat capacity|heat capacities]] of [[substance]]s. Data produced by calorimeters has been foundational to the development of such technologies as [[steam boiler]]s, [[turbine]]s, [[rocket engine]]s, [[internal combustion engine]]s, oil refineries, and plastic product factories.
-[[Water]] has become a widely accept standard material for use in calorimeters because it has a high and precisely measured heat capacity, is easy to work with, and is readily available. A simple type of calorimeter would consist of an insulated container of water with a thermometer fixed in the water. A measurement of the caloric(heat) content of broccoli, for example, would require first drying a measured quantity of broccoli then burning it inside a calorimeter container heat capacity, for example, of copper, could be made by heating a chunk of copper of a measured size to a measured elevated temperature, then placing the copper chunk in the water.
+A widely accepted standard reference material used in many calorimeters is water because it has a high and precisely measured heat capacity, is easy to work with, and is readily available. A simple type of calorimeter would consist of an insulated container of water with a thermometer fixed in the water. To measure the heat capacity of molten lead, for example, an investigator could place a bowl of molten lead inside the calorimeter and record the temperature drop of the cooling lead and the corresponding temperature rise of the water. Knowing the mass of both the water and the lead, the investigator would have enough information to calculate lead's heat capacity.
-The method or process of carrying out such measurements is called '''calorimetry'''.
+Calorimeters come in many different types, some targeted to measuring the heat capacity of new materials (differential scanning calorimeters), while others measure such diverse aspects as the heat generated by new or untested reactions (isothermal microcalorimeters), heat of combustion and burn rates (accelerated rate calorimeters), and the energy of elementary particles (electromagnetic and hadronic calorimeters).
-The word ''calorimeter'' is derived from the [[Latin]] word ''calor'', meaning [[heat]]. Differential Scanning Calorimeters, Isothermal Microcalorimeters, Titration Calorimeters and Accelerated Rate Calorimeters are among the most common types.
+The word "calorimeter" is derived from the [[Latin]] word ''calor,'' meaning [[heat]]. The method or process of carrying out such measurements is called '''calorimetry.'''
-A simple calorimeter just consists of a thermometer attached to an insulated container. To find the [[enthalpy]] change per mole of a substance X in a reaction between two liquids X and Y, they are added to the calorimeter and the initial and final (after the reaction has finished) [[temperature]]s are noted. Multiplying the temperature change by the mass and [[specific heat capacity|specific heat capacities]] of the liquids gives a value for the [[energy]] given off during the reaction (assuming the reaction was exothermic.) Dividing the energy change by how many moles of X were present gives its enthalpy change of reaction.  This method is used primarily in academic teaching as it describes the theory of calorimetry.  It doesn’t however 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. This shows that the matter can be neither created nor destroyed.
+==Representative calculations==
+Calculating the heat capacity of molten lead based on data collected in the example above requires using the formula
-==Types==
+Q = ''sm''ΔT
-===Reaction Calorimeters===
-[[Image:Lara_Coflux.jpg|right|150px|thumb| An example of a [[Reaction calorimeter]]]]
-A '''[[Reaction calorimeter]]''' is a calorimeter in which a [[chemical reaction]] is initiated within a vessel. 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 three common methods for measuring heat in reaction calorimeter:
-'''Heat flow calorimetry'''
+where Q is the quantity of heat, ''s'' is the specific heat(the material's heat capacity divided by the heat capacity of water), ''m'' is the mass of the material, and ΔT is the temperature change. Inside the calorimeter, the heat lost by the lead(Q<sub>l</sub>) is, to the first approximation, equal to the heat gained by the water(Q<sub>w</sub>]). In this case, (''sm''ΔT)<sub>l</sub> must be equal to (''sm''ΔT)<sub>w</sub>. Since the only unknown quantity here is ''s<sub>l</sub>,'' it can be calculated according to the formula
-The cooling/heating jacket controls the temperature of the process. Heat is measured by monitoring the temperature difference between heat transfer fluid and the process fluid as follows:
-<math>Q = UA(T-t)</math>
+''s<sub>l</sub>'' = (''sm''ΔT)<sub>w</sub>/(''m''ΔT)<sub>l</sub>
+To gain more insight about the complex energy dynamics operative in even the most inert and quiet looking piece of matter, scientists apply calorimetric measurements to the subtle concept of [[enthalpy]], a measure of the internal energy of a system at constant pressure. For each substance, its internal energy content (U) as embodied in the movements of its molecular and atomic level components is distinctively dependent not only on the temperature (T) but on the pressure (P) and volume (V).
-where
+[[Enthalpy]] (H) is defined as H = U + PV. In words, enthalpy change (ΔH) is the amount of heat released or absorbed when a chemical reaction occurs at constant pressure. (Standardized enthalpy measurements are often expressed in terms of 1 [[mole(chemistry)|mole]] of a substance X, which is a quantity of X equal to the molecular weight of X expressed in grams.) To find the enthalpy change per mole of a liquid substance X, for example, in reaction with liquid Y, the two liquids are mixed inside the calorimeter and the initial and final (after the reaction has finished) [[temperature]]s are noted. Working with the basic formula, Q = ''sm''ΔT and multiplying the temperature change times the masses and the [[specific heat capacity|specific heat capacities]] of the two liquids permits a further calculation that yields a value for the [[energy]] given off during the reaction (assuming the reaction was exothermic). Dividing the energy change by the number of moles of X present gives its enthalpy change of reaction.  This method is used primarily in academic teaching, as it describes the theory of calorimetry.  It doesn’t, however, account for heat loss through the container or the heat capacity of the thermometer and container itself.
-:<math>Q</math> = process heating (or cooling) power (W)
+==Types==
-:<math>U</math> = overall heat transfer coefficient (W/(m<sup>2</sup>K))
+===Reaction calorimeters===
-:<math>A</math> = heat transfer area (m<sup>2</sup>)
+[[Image:Lara_Coflux.jpg|right|150px|thumb| An example of a [[Reaction calorimeter]]]]
-:<math>T</math> = process temperature (K)
+A '''[[Reaction calorimeter]]''' measures the heat energy released or absorbed during a reaction that occurs inside the calorimeter.  This is the standard instrument used for measuring heats of industrial processes. Reaction calorimetry can also be used for determining the maximum rate of heat release in chemical process engineering.
-:<math>t</math> = jacket temperature (K)
-Heat flow calorimetry allows the user to measure heat whilst the process temperature remains under control. It is however a difficult technique to use and not particularly accurate. The value of U has to be predetermined by careful experimentation and any change in product composition, liquid level, process temperature, agitation rate or viscosity will upset the calibration.
-A variation of the 'heat flow' technique is called 'Power Compensation' Calorimetry. This method uses a cooling jacket operating at constant flow and temperature. The process temperature is regulated by adjusting the power of the electrical heater. When the experiment is started, the electrical heat and the cooling power (of the cooling jacket) are in balance. As the process heat load changes, the electrical power is varied in order to maintain the desired process temperature. The heat liberated or absorbed by the process is determined from the difference between the initial eletrical power and the demand for electrical power at the time of measurement. The power compensation method is easier to set up than heat flow calorimetry but it suffers from the similar limitations since any change in product composition, liquid level, process temperature, agitation rate or viscosity will upset the calibration. The presence of an electrical heating element is also undesirable for process operations.
-'''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 as follows:
-<math>Q = m_s C_{ps}(T_i - T_o)</math>
-where
-:<math>Q</math> = process heating (or cooling) power (W)
-:<math>m_s</math> = mass flow of heat transfer fluid (kg/s)
-:<math>C_{ps}</math> = specific heat of heat transfer fluid (J/(kg K))
-:<math>T_i</math> = inlet temperature of heat transfer fluid (K)
-:<math>T_o</math> = outlet temperature of heat transfer fluid (K)
-Heat balance calorimetry is, in principle, the ideal method of measuring heat since the heat entering and leaving the system through the heating/cooling jacket is measured from the heat transfer fluid (which has known properties). This eliminates most of the calibration problems encountered by heat flow and power compensation calorimetry. Unfortunately, the method does not work well in traditional batch vessels since the process heat signal is obscured by large heat shifts in the cooling/heating jacket. A recent development in calorimetry however is that of constant flux cooling/heating jackets. These use variable geometry cooling jackets and can operate with cooling jackets at substantially constant temperature. These reaction calorimeters tend to be much simpler to use and are much more tolerant of changes in the process conditions (which would affect calibration in heat flow or power compensation calorimeters).
 ==== Bomb calorimeters ====
+A bomb calorimeter is a type of reaction calorimeter used for measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand strong pressure and force as the reaction is being measured. Electrical energy is used to ignite the fuel. As the fuel burns, it heats up the surrounding air, which expands and escapes through a copper tube passing through water on the way out of the calorimeter. The temperature change of the water heated by the air escaping through the copper tube provides the measurement needed to calculate the energy content of the fuel.
-A bomb calorimeter is a type of calorimeter used in measuring the heat of combustion of a particular reaction. Bomb calorimeters have to withstand the large pressure and force of 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 around 30 atm) and containing a known mass of fuel, is submerged under a known volume of water before the charge is (again, electrically) ignited. 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 burning fuel. A small correction is made to account for the electrical energy input and the burning fuse.
-In more recent calorimeter designs the whole bomb, pressurized with excess pure oxygen (typically @30atm) and containing a known mass of fuel, is submerged under a known volume of water before the charge is (again electrically) ignited. 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 fuel burnt. A small correction is made to account for the electrical energy input and the burning fuse.
-In simple terms it is better than a simple calorimeter because it doesn't allow as much unmeasured heat loss.
-===Constant-pressure===
-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 and 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]].
 ===Differential scanning calorimeter===
 {{main|Differential scanning calorimeter}}
-In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminum]] capsule or 'pan'—is measured differentially, i.e., by comparing it to the flow into an empty reference pan.
+In a '''differential scanning calorimeter''' (DSC), [[heat flow]] into a sample—usually contained in a small [[aluminum]] capsule or "pan"—is measured differentially; that is, 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 = &beta;
-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]] ''C<sub>p</sub>''. The difference in flow ''dq''/''dt'' induces a small temperature difference &Delta;''T'' across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal:
+In a '''heat flux DSC,''' both pans sit on a small slab of material with a known heat resistance. The temperature of the calorimeter is raised at a constant heating rate, an objective that requires good design and good (computerized) temperature control. A heat flux DSC can also be used for experiments requiring controlled cooling or constant temperature.
-<math>\Delta T = K {dq\over dt} = K C_p\, \beta</math>
+During the experiments, heat flows into the two pans by conduction, with the flow of heat into the sample being larger because of the sample's larger [[heat capacity]]. The difference in the heat flow into the two pans induces a small temperature difference across the slab. This temperature difference is measured using a [[thermocouple]]. The heat capacity can in principle be determined from this signal. Differential scanning calorimetry is a workhorse technique in many fields, particularly in [[polymer]] characterization.
-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:
-&Delta;V = 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.
 ===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)
+In an '''isothermal [[titration]] calorimeter,''' the heat of reaction is used to follow a titration experiment, one in which the concentration of an unknown reagent is determined by using a standard concentration of another reagent that chemically reacts with the unknown. This permits determination of the mid point of a reaction as well as other key parameters. The technique is gaining 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.
-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.
 ===X-ray microcalorimeter===
 [[Image:X-ray microcalorimeter diagram.jpg|thumb|270px|X ray microcalorimeter diagram]]
-In [[1982]], a new approach to non-dispersive [[X-ray spectroscopy]], based on the measurement of heat rather than charge, was proposed by Moseley et al. (1984). The detector, and X-ray microcalorimeter, works by sensing the heat pulses generated by X-ray [[photons]] when they are absorbed and thermalized. The temperature increase is directly proportional to photon energy. This invention combines high detector efficiency with high energy resolution, mainly achievable because of the low temperature of operation.  Microcalorimeters have a low-heat-capacity mass that absorbs incident X-ray (UV, visible, or near IR )  photons, a weak link to a low-temperature [[heat sink]] which provides the thermal isolation needed for a temperature rise to occur, and a thermometer to measure change in temperature. Following these ideas, a large development effort started. The first astronomical spacecraft that was designed, built and launched with embarqued cryogenic microcalorimeters was [[Astro-E2]]. [[NASA]] as well as  [[ESA]] have plans for future missions ([[Constellation-X]] and [[XEUS]], respectively) that will use some sort of micro-calorimeters.
+In 1982, a new approach to non-dispersive [[X-ray spectroscopy]], based on the measurement of heat rather than charge, was proposed by Moseley et al. (1984). The detector, which is the basis of the X-ray microcalorimeter, works by sensing the heat pulses generated by X-ray [[photons]] when they are absorbed into a material as heat energy. The temperature increase is directly proportional to photon energy. This invention combines high detector efficiency with high energy resolution, mainly achievable because it is operated at a low temperature.
+These cryogenic microcalorimeters have a thermometer to measure the change in temperature of a low-heat-capacity mass that can in principle absorb incident photons not only in the X-ray range, but also in the ultraviolet, visible, or near infrared ranges. This mass is connected by a weak link to a low-temperature [[heat sink]], which provides the thermal isolation needed for a temperature rise to occur. Building on the original innovative approach, a large development effort is still expanding the field of cryogenic microcalorimetry. The first astronomical spacecraft carrying cryogenic microcalorimeters was the orbiting x-ray observatory Suzaku/[[Astro-E2]]launched in July 2005. [[NASA]] as well as [[ESA]] have plans for future missions ([[Constellation-X]] and [[XEUS]], respectively) that will use some sort of micro-calorimeters.
 ===High-energy particle calorimeter===
-{{main|calorimeter (particle physics)}}
 In [[particle physics]], a calorimeter is a component of a [[particle detector|detector]] that measures the [[energy]] of entering [[Subatomic particle|particle]]s.
 == Calorimetry ==
-Calorimetry is the science of measuring the [[heat]] of [[chemical reaction]]s or [[physical change]]s. Calorimetry involves the use of a calorimeter.
+As scientists have developed and worked with calorimeters, the new field of calorimetry has developed in parallel with the mission of measuring the quantity of [[heat]] absorbed or released when matter undergoes a change in its physical, chemical, or electrical state. As a field of study in its own right, calorimetry overviews the whole history and range of calorimeters and provides a useful way of looking at their different types.
-"Indirect calorimetry" calculates [[heat]] that living organisms produce from their production of [[carbon dioxide]] and nitrogen waste (frequently [[ammonia]] in aquatic organisms, or [[urea]] in terrestrial ones), or from their consumption of [[oxygen]]. Lavoisier noted in 1780 that heat production can be predicted from oxygen consumption this way, using [[multiple regression]]. The [[Dynamic Energy Budget]] theory explains why this procedure is valid. Of course, heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.
-===Changes of temperature and internal energy===
-If an object or system is isolated from the rest of the universe, its temperature must stay constant.  On the other hand, if energy enters or leaves the system, its temperature must change. The transfer of energy from one place (or system) to another is called  '''[[heat]]''', and calorimetry tracks the movement of heat by measuring temperature changes and [[heat capacity|heat capacities]].
+"Indirect calorimetry" calculates the [[heat]] generated by living organisms when their metabolic processes yield waste [[carbon dioxide]] and nitrogen. [[Lavoisier]] noted in 1780 that heat production can be predicted from oxygen consumption by living organisms. The [[Dynamic Energy Budget]] theory explains why this procedure is valid. Of course, heat generated by living organisms may also be measured by direct calorimetry, in which the entire organism is placed inside the calorimeter for the measurement.
 ====Constant-volume====
-''Constant-volume calorimetry'' is calorimetry performed at a constant [[volume]]. This involves the use of a [[constant-volume calorimeter]].
+Constant-volume calorimetry using a [[constant-volume calorimeter]], constrains the test system to perform no work, so the heat gain or loss measured equals the change in internal energy of the system. The equation for constant-volume calorimetry is:
-No work is performed in constant-volume calorimetry, so the heat measured equals the change in internal energy of the system. The equation for constant-volume calorimetry is:
 :<math>q = C_V \Delta t = \Delta U \,</math>
@@ Line 128: / Line 70: @@
 :''ΔU'' = change in [[internal energy]]
+:''C<sub>V</sub>'' = heat capacity of the system of volume V
-Since in ''constant-volume calorimetry'' the [[pressure]] is not kept constant, the heat measured does not represent the ''[[enthalpy]] change''.
+Since in constant-volume calorimetry the [[pressure]] is not kept constant, the heat measured does not represent the [[enthalpy]] change.
 ====Constant-pressure====
-''Constant-pressure calorimetry'' is calorimetry performed at a constant [[pressure]]. This involves the use of a [[constant-pressure calorimeter]].
+Constant-pressure calorimetry uses a [[constant-pressure calorimeter]] measures a quantity of heat energy exchange equal to the change in internal energy of the system minus the work (w) performed:
-The heat measured equals the change in internal energy of the system minus the work performed:
 : <math> q = \Delta U - w  \,</math>
-Since in ''constant-pressure calorimetry'', [[pressure]] is kept constant, the heat measured represents the ''enthalpy change'':
+Since in ''constant-pressure calorimetry,'' [[pressure]] is kept constant, the heat measured represents the ''enthalpy change:''
 : <math>q = \Delta H = H_\mathrm{final} - H_\mathrm{initial} \,</math>
-==See also==
-*[[Enthalpy]]
-*[[Heat]]
-*[[Calorie]]
-*[[Heat of combustion]]
-*[[Calorimeter constant]]
-* [[Thermodynamic databases for pure substances]]
-{{LaboratoryEquipment}}
 == Notes ==
@@ Line 158: / Line 88: @@
 == References ==
-<<3 reliable references needed here, properly formatted.>>
+*Larijani,Bananshé, Colin A. Rosser, and Rudiger Woscholski, ed. 2006. ''Chemical Biology: Techniques and Applications''. West Sussex, England: John Wiley and Sons, Ltd. ISBN-13 978-0-470-09064-0
+*Beezer, A.E., ed. 1980. ''Biological Microcalorimetry''. New York: Academic Press, Inc.  ISBN 0-12-083550-9
-==External links==
+Besancon, Robert M., ed. 1985. ''The Encyclopedia of Physics,'' 3rd ed. New York: Van Nostrand Reinhold Company. ISBN 0-442-25778-3
-* [http://http://www.helgroup.com/home/reactor-systems/safety.html HEL Reaction Calorimetry]
-*[http://www.ashemorris.com/batch-technologies.aspx Industrial Calorimeters]
-*[http://www.syrris.com/coflux.aspx Constant Flux Calorimetry]
 [[Category:Physical sciences]]
 [[Category:Physics]]
 [[Category:Chemistry]]
-[[Category:Thermochemistry]]
 {{credits|Calorimeter|135905740|Calorimetry|134453621}}