The two carried out some of the earliest thermochemical investigations, devised apparatus for measuring linear and cubical expansions, and employed a modification of Joseph Black's ice calorimeter in a series of determinations of specific heats.
Davy, Count Rumford, all concerned themselves with thermochemical investigations of such processes.
Hess (18 4 o) were the first who systematically investigated thermochemical effects in solution, and arrived at conclusions from their experimental data which still possess validity.
Julius Thomsen was the first investigator who deliberately adopted the principle of the conservation of energy as the basis of a thermochemical system.
His thermochemical work was begun in 1853, but most of his experiments were performed in the years 1869-82, the whole being published collectively, under the title Thermochemische Untersuchungen, in four volumes.