Calorimetry involves measurements of enthalpy changes in various processes like mixing, dilution, dissolution, crystallization, adsorption or in a chemical reaction. In addition, it is used for the determination of heat capacities. Calorimetry can be oftwo types: adiabatic or isothermal. In anadiabatic calorimeter no heat is exchanges with surroundings and hence temperature change is to be monitored during the process occuring in the calorimeter. In such a case the accuracy of measurement of any physical property using a calorimeter depends on the accuracy of temperature measurement and how good the adiabatic shield is.

A vacuum ask/Dewar ask is used as an adiabatic calorimeter. However, minute "heat leaks" are not uncommon. In order to reduce heat flow to or from the surroundings, the Dewar ask itself should be placed in a constant temperature container such as a large thermostat or insulated box whose temperature should be regulated as close to the contents of the Dewar flask as possible. Care should be taken so that "heat leak" does not occur through either the lid of the Dewar ask or openings in the lid. If the instrument is sensitive enough, stirring of the contents would also be controlled and its effect should be monitored in a blank experiment.

Figure : A schematic diagram of a Calorimeter.

D = Glass Dewar Flask of capacity 100 ml, S = Polypropylene Stopper, H = Resistance Heater, ST= Stirrer, T = Temperature Sensor