[f. THERMO- + CHEMISTRY.] That branch of chemical science that deals with the quantities of heat evolved or absorbed when substances undergo chemical change or enter into solution; e.g., the amount of heat evolved when hydrogen burns in oxygen or when sodium hydroxide is neutralized by sulphuric acid. Also sometimes used in a wider sense to include all relations of heat to substances, such as conductivity, specific heat, etc.
1844. Joule, in L. E. & D. Philos. Mag. (1845), May, 382. The phænomena described in the present paper, as well as most of the facts of thermo-chemistry, agree with this theory.
1880. Cleminshaw, Wurtz’ Atom. The., 330. It is useless to bring forward in opposition to the hypothesis of atoms considerations drawn from thermo-chemistry.
1901. Westm. Gaz., 16 Dec. Up to the war of 1870 his [Berthelot’s] time was mainly spent on researches in the region of physical chemistry, culminating in the foundation of a new science—that of thermo-chemistry.
So Thermochemic, Thermochemical adjs., of or pertaining to thermochemistry; Thermochemically adv., by means of or with reference to thermochemistry; Thermochemist, one who is skilled in thermochemistry.
1871. Thomsen, in Jrnl. Chem. Soc., XXIV. 878. On the Inaccuracy of Favre and Silbermann’s *Thermochemical Determinations made with the Mercury Calorimeter.
1880. Cleminshaw, Wurtz’ Atom. The., 330. Thermo-chemical facts agree perfectly with the atomic hypothesis.
1901. Nature, 24 Oct., 644/1. A thermochemical comparison of the action of acids upon oxide of silver before and after the action of hydrogen peroxide. Ibid. (1890), 18 Dec., 165/2. *Thermochemists … attempt to draw an impossible distinction between chemical and physical changes.
