“Van’t Hoff had shown chemists how thermodynamics could be applied to their science, especially with reference to ideas on affinity. In his work in 1884 he first drew the distinction between chemical kinetics and chemical thermodynamics and showed that the maximum external work obtained when a chemical reaction was carried out reversibly and isothermally could serve as a measure of chemical affinity. Helmholtz even earlier had called maximum work ‘free energy’. Gilbert Lewis, of the University of California, Berkeley, proposed that this term be restricted to mean the work available for use. Thus, the maximum useful work obtained when one system passes spontaneously into another represents the decrease in free energy of the system. The influential textbook of G.N. Lewis and Merle Randall which represents these ideas has led to a replacement of the term ‘affinity’ by the term ‘free energy’ in much of the English-speaking world. The older term has never been entirely replaced in thermodynamic literature, since after 1922 the Belgian school under Theophile De Donder has made the concept of affinity still more precise.”

“The influential textbook of G.N. Lewis and Merle Randall led to the replacement of the term ‘affinity’ by the term ‘free energy’ throughout the English speaking world.”