DEFINITION
A calorimeter is an apparatus for measuring heat quantities generated in or emitted by materials in processes such as chemical reactions, changes of state, or formation of solutions[1].
INVENTION
The French scientists Antoine-Laurent de Lavoisier and Pierre-Simon Laplace invented[2] the calorimeter in 1780 to research the amount of heat released or absorbed by various substances and chemical reactions. Here is a diagram of the exterior of the calorimeter they constructed: