In chemistry, thermal theory of affinity, or "heat theory of affinity", was a 19th century posited argument which asserted that all chemical action not due to external energy tends to the production of the body or bodies which set free the greatest heat. [1] Synonyms include: principle of maximum work, law of maximum work, Thomsen-Berthelot principle, and Berthelot-Thomsen principle.

Overview
The theory was independently proposed by Danish chemist Julius Thomsen (1854) and French chemist Marcellin Berthelot (1864), but disproved in 1882 by German physicist Hermann Helmholtz, and replaced by the thermodynamic theory of affinity.

In 1887, German chemist Lothar Meyer, in his “Evolution of the Doctrine of Affinity”, have a cogent rise and fall account of the thermal theory of affinity. [4]

In the 1980s, German chemistry historian Helge Kragh is said to have provided the the bulk of the references to the literature on the thermal theory of affinity. [2]

Quotes
The following are related quotes:

“The thermal theory of affinity, which is even today championed by Berthelot and others, is by this circumstance proved to be quite untenable. It is natural, in the case of such a far-reaching proposition, to require proofs.”
Wilhelm Ostwald (1893), “On Chemical Energy” [3]

References
1. (a) Sprague, John T. (1892). Electricity: its Theory, Sources, and Applications (pg. 305). E. & F.N.
(b) Thims, Libb. (2007). Human Chemistry (Volume Two) (thermal theory of affinity, pg. 434). Morrisville, NC: LuLu.
2. (a) Kragh, Helge. (1993). “Between Physics and Chemistry: Helmholtz’s Route to a Theory of Chemical Thermodynamics”, in Hermann von Helmholtz and the Foundations of Nineteenth-Century Science (thermal theory of affinity, 8+ pgs.; ch. 10, pgs. 402-31), ed. David Cahan. University of California Press.
(b) Kragh, Helge. (1984). “Julius Thomsen and Classical Thermochemistry”, BJHS, 17: 255-72.
(c) Dolby, R.G.A. (1984). “Thermochemistry versus Thermodynamics: the Nineteenth-century Controversy”, History of Science, 22: 375-400.
3. Ostwald, Wilhelm. (1893). “On Chemical Energy” (abs), Journal of the American Chemical Society, 15(8):421-30.
4. Meyer, Lothar. (1887). “Evolution of the Doctrine of Affinity” (translator: William Ramsay) (abs) (ΡΊ) (thermal theory of affinity, pgs. 508-11), Philosophical Magazine, 23(145):504-12.

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