calorimeter (bomb calorimeter) An instrument for measuring the amount of oxidizable energy in a substance, by burning it in oxygen and measuring the heat produced. The energy yield of a foodstuff in the body is equal to that obtained in a bomb calorimeter only when the metabolic end‐products are the same as those obtained by combustion. Thus, proteins liberate 5.65 kcal (23.64 kJ)/g in a calorimeter, when the nitrogen is oxidized to the dioxide, but only 4.4 kcal (18.4 kJ)/g in the body, when the nitrogen is excreted as urea (which has a heat of combustion equal to the ‘missing’ 1.25 kcal (5.23 kJ)).

calorimeter Any of various devices used to measure thermal properties, such as calorific value. See bomb calorimeter.

calorimeter (kal-er-im-it-er) n. any apparatus used to measure the heat lost or gained during various chemical and physical changes. Calorimeters are used to determine the energy value of different foods.
—calorimetry n.