Title page to the 1923 Thermodynamics by Gilbert Lewis and Merle Randall, the core book of modern chemical thermodynamics, which into the 1960s was being proclaimed as the 'bible' for students of chemist in this field.

In thermodynamics, chemical thermodynamics is the energetic and entropic study of physical processes or chemical reactions. [1] The central aspects of study in chemical thermodynamics are the initial and final states of the process or reaction. If the energy and entropy are known, with respect to appropriate reference points, for all values of pressure, volume, and temperature to be covered in the investigation, then the thermodynamic examination can be a complete one. [1] In this sense, chemical thermodynamics is the study of energy, entropy, and equilibrium in chemical systems. [4] English physical chemist Brian Smith, gives an excellent description on the wondrous yet cautious intrigue many have with their first encounter with chemical thermodynamics: [5]

“The first time I heard about chemical thermodynamics was when a second-year undergraduate brought me the news early in my freshman year. He told me a spine-chilling story of endless lectures with almost three-hundred numbered equations, all of which, it appeared, had to be committed to memory and reproduced in exactly the same form in subsequent examinations. Not only did these equations contain all the normal algebraic symbols but in addition they were liberally sprinkled with stars, daggers, and circles so as to stretch even the most powerful of minds.”

Chemical thermodynamics is generally considered the most difficult subjects in all of science.

History

See main: History of chemical thermodynamics

American chemist Mary Jo Nye correctly summarizes the prehistory of chemical thermodynamics in the following quote: [9]

“The roots of both chemical thermodynamics and contemporary chemical kinetics both lie in the eighteenth-century ideas of chemical ‘affinity’ and ‘force’, transformed into the nineteenth-century conceptions of ‘work’ and ‘energy’.”

German physical chemist August Horstmann was said to have done the first work in chemical thermodynamics. In circa 1865, he began to study the works of Rudolf Clausius for applications in the calculation of equilibriums in chemical systems. His 1869 paper "Dampfspannung und Yerdampfungswärme des Salmiaks" was the first to apply entropy to chemical problems. In October 1873, Horstmann announced the condition for chemical equilibrium to be that of maximum entropy. [7]

In December of 1873, independent of Horstmann, American mathematical physicist Willard Gibbs, in a footnote, stated that the condition for thermodynamic equilibrium in a chemical system at constant temperature and pressure is that a certain function, now universally known as the thermodynamic potential, should be a minimum. [8] Gibbs, however, would go on to present a more complete and rigorous treatise on the subject of equilibriums. Specifically, the two central founders of chemical thermodynamics are generally considered to be Gibbs, with the publication of his 1876 On the Equilibrium of Heterogeneous Substances, and German physician and physicist Hermann von Helmholtz (a mentor to Horstmann), with the publication of his 1882 The Thermodynamics of Chemical Processes (Die Thermodynamik Chemischer Vorgänge). [2]

The year 1876, with the work of Gibbs, however, is the generally agreed upon year in which chemical thermodynamics was born. As Gibbsian biographer Lynde Wheeler tells, the development of the prime or fundamental equation of Gibbs:

or in modern notation:

which is the core equation of Gibbs' Equilibrium treatise, "marks the birth of the theory of chemical thermodynamics". [10]

In 1913, English chemist James Partington published his Text-book of Thermodynamics with Special Reference to Chemistry, followed by his 1924 updated second edition titled Chemical Thermodynamics. [6]

The founders of "modern" chemical thermodynamics are American physical chemists Gilbert Lewis and Merle Randall, for the publication of their 1923 Thermodynamics and the Free Energy of Chemical Substances, in which they were the first to apply the principles of Gibbs specifically to chemical processes, and English physical chemist Edward Guggenheim, for his 1933 Modern Thermodynamics by the Methods of Willard Gibbs. Together, the three of them unified the science of chemical thermodynamics into a coherent whole. [3]

Etymology

See main: Thermodynamics (naming)

In naming new branches of thermodynamics, a rule followed is that (a) the additive new subject (e.g. chemistry) is affixed with the appropriate suffix (e.g. -ary, -ical, –al, etc.) and (b) the new core subject is followed by the word “thermodynamics”. The following publication timeline table shows the progressive emergence of the branch of thermodynamics called specifically 'chemical thermodynamics':

Date	Publication	Author [s]
1869	"Dampfspannung und Yerdampfungswärme des Salmiaks" (Vapor Pressure and Yerdampfungswärme of Ammonium Chloride)	August Horstmann
1873	"Graphical Methods in the Thermodynamics of Fluids"	Willard Gibbs
1873	"A Method of Geometrical Representation of the Thermodynamic Properties of Substances by Means of Surfaces"	Willard Gibbs
1876	On the Equilibrium of Heterogeneous Substances	Willard Gibbs
1882	"The Thermodynamics of Chemical Processes"	Hermann Helmholtz
1884	Studies in Chemical Dynamics	Jacobus van't Hoff
1903	Treatises on the Thermodynamics of Chemical Processes	August Horstmann
1903	Thermodynamics and Chemistry: A Non-mathematical Treatise for Chemists and Students of Chemistry	Pierre Duhem
1907	Thermodynamics and Chemistry	Frank Henry Macdougall
1907	Experimental and Theoretical Applications of Thermodynamics to Chemistry	Walther Nernst
1912	A Text Book of Thermo-Chemistry and Thermodynamics	Otto Sackur
1913	Text-book of Thermodynamics with special reference to Chemistry	James Partington
1923	Thermodynamics and the Free Energy of Chemical Substances	Gilbert Lewis and Merle Randall
1924	Chemical Thermodynamics	James Partington
1928	The Fundamentals of Chemical Thermodynamics	John Butler
1933	Modern Thermodynamics by the Method of Willard Gibbs	Edward Guggenheim
1946	Thermodynamics for Chemists	Samuel Glasstone
1949	Thermodynamics: Advanced Treatment for Chemists and Physicists	Edward Guggenheim
1950	Chemical Thermodynamics	Ilya Prigogine and Raymond Dufay
1950	Chemical Thermodynamics	Frederick Rossini
1950	Chemical Thermodynamics: Basic Theory and Methods	Irving Klotz
1959	An Introduction to the Study of Chemical Thermodynamics	D. H. Everett
1962	Elements of Chemical Thermodynamics	Leonard Nash
1963	Elementary Chemical Thermodynamics	Bruce Mahan
1965	Chemical Thermodynamics	John Kirkwood and Irwin Oppeheim
1965	Chemical Thermodynamics: a Course Study	Frederick Wall
1966	Basic Chemical Thermodynamics	Jurg Waser
1969	Chemical Thermodynamics	Peter Rock
1969	Chemical Thermodynamics	Ilya Prigogine and Raymond Dufay
1973	Basic Chemical Thermodynamics	Brian Smith
1990	Chemical Thermodynamics	Charles Reid
1990	Thermodynamics of Chemical Systems	Scott Wood and Rubin Battino
2000	Chemical Thermodynamics: Principles and Applications	Bevan Ott and Juliana Goates

Thus, given the above rule, the subject of "thermodynamics and chemistry" (1880s) became "chemical thermodynamics" (1920s) over a period of forty years. Hence, if one is to learn by example, in the naming of a new branch of thermodynamics, e.g. "the thermodynamics of surface interactions", one should skip to the chase (e.g. surface thermodynamics), and save years of thought on questions regarding name choice. In the 1940s, to note, the specialty branch of chemical engineering thermodynamics began to develop.

References
1. Rossini, Frederick D. (1950). Chemical Thermodynamics, New York: John Wiley & Sons, Inc.
2. (a) Helmholtz, Hermann von. (1882). “Die Thermodynamik Chemischer Vorgänge (The Thermodynamics of Chemical Operations”, SB: 22-39, in Wissenschaftliche Abhandlungen von Hermann von Helmholtz. 3 vols. Leipzig: J.A. barth, 1882-95. 2:958-78.
(b) Cahan, David. (1993). Hermann von Helmholtz and the Foundations of Nineteenth-Century Science, (ch. 10: "Between Physics and Chemistry - Helmholtz's Route to a Theory of Chemical Thermodynamics", pg. 403-31). Berkeley: University of California Press.
3. Boerio-Goates, Juliana, and Ott, J., Bevan. (2000). Chemical Thermodynamics - Principles and Applications, (pg. 1-2). New York: Elsevier Academic Press.
4. Balzhiser, Richard, E., Samuels, Michael R., and Eliassen, John, D. (1972). Chemical Thermodynamics - the Study of Energy, Entropy, and Equilibrium. Englewood Cliffs, New Jersey: Prentice-Hall, Inc.
5. Smith, Brian E. (2005). Basic Chemical Thermodynamics. Imperial College Press.
6. Partington, J.R. (1924). Chemical Thermodynamics: An Introduction to General Thermodynamics and its Applications to Chemistry. D. Van Nostrand.
7. Horstmann, August F. (1973). “Theorie der Dissociation”, Liebig’s Annalen der Chemie und Pharmacie, Bd. 170 (CLXX), 192-210.
8. (a) Gibbs, Willard. (1873). Trans. Connect. Acad., Dec., II., footnote to pg. 393.
(b) Garrison, Fielding H. (1909). “Josiah Willard Gibbs and his Relation to Modern Science”, Popular Science, pgs. 470-84.
9. Nye, Mary Jo. (1993). From Chemical Philosophy to Theoretical Chemistry: Dynamics of Matter (pg. 117). University of California Press.
10. Wheeler, Lynde Phelps. (1951). Josiah Willard Gibbs: the History of a Great Mind (pg. 77). Ox Bow Press.

Further reading
● Pauling, Linus. (1970). “History of Chemical Thermodynamics”, in The Centennial of the Sheffield Scientific School (pgs. 27-32) by Baitsell, George A. and Lawrence, Ernest O. Ayer Publishing.

External links
● Chemical thermodynamics - Wikipedia.
● International Conference on Chemical Thermodynamics - IACT.