Calorimeters place much emphasis on insulating the reaction to prevent heat loss. The bomb calorimeter (so called because the pressurized reaction vessel burns the sample near instantaneously in a high oxygen atmosphere, or explosively) submerges the reaction inside an insulated container of water. An electrical heating device starts the reaction inside a sealed reaction vessel and the temperature rise of the water which surrounds it is measured. Bomb calorimeters are often used to find the calorific value - energy content - of foods.
Inevitably there will always be some heat loss from a calorimeter. One method of accounting for this is to use an electrical heater to produce the same temperature change over the same time period in the calorimeter as the reaction being measured. The electrical energy supplied to produce the temperature change is equal to the energy change that occurred in the reaction. Another method is to keep the temperature of the water surrounding the reaction vessel constant by heating or cooling it, and to measure the energy that is required to do this. This can then be used in calculations to produce extremely accurate results for energy changes.
