In chemistry, thermo-chemistry is the study of the function of heat and temperature involved in chemical transformation. In modern physical chemistry, thermochemistry is defined as a subject concerned with heats of chemical reactions, heats of formations, etc. [1]

History
The conjunctional term “thermo-chemistry” dates to at least 1840. In fact, German physical chemist Wilhelm Ostwald cites Swiss-born Russian chemist Germain Hess, with his 1840 article “Constant Heat Sums” (Constanz der Warmesummen), which established Hess’ law, as being the founder of thermo-chemistry. [2] English chemistry historian James Riddick, however, attributes the construction of the ice-calorimeter, used in the winter of 1782-83, by French chemist Antoine Lavoisier and mathematician Pierre-Simon Laplace, used to determine the heat evolved in various chemical changes; calculations which were based on Scottish physicist Joseph Black’s prior discovery of latent heat, as experiments that marked the foundation of thermochemistry. [3]

After the formulation of entropy in 1865, the field of thermochemistry tended to be subsumed into the new field of chemical thermodynamics, in larger part.

References
1. Daintith, John. (2004). Oxford Dictionary of Chemistry. Oxford University Press.
2. Meyer, Ernst von. (1898). A History of Chemistry from the Earliest Times to the Present Day. (pg. 507). The Macmillan Company.
3. Partington, J.R. (1957). A Short History of Chemistry. MacMillan and Co.

External links
● Thermochemistry – Wikipedia.