In 1783, Antoine Lavoisier, in his Memoir on Heat, using the Papin digester (1679), Papin engine (1690), and Boerhaave law (1720s) as a basis, introduced the verbal outline of the reversible heat cycle.
In 1824, Sadi Carnot, in his On the Motive Power of Fire, building on Lavoisier and Papin, introduced the Carnot cycle or Lavoisier-Carnot cycle, as shown adjacent, according to which so many "caloric" particles go into the system or working body, causing the working body to expand, and at the end of the cycle, the exact same number of caloric particles come out.
Equivalence value model
The following are related quotes:
- “He was a practical electrician fond of whiskey, a heavy, red-haired brute with irregular teeth. He doubted the existence of a deity but accepted Carnot's cycle, and he had read Shakespeare and found him weak in chemistry.”
- — Herbert Wells (1906), "Lord of the Dynamos"
- “Where does the Carnot cycle fit into chemistry. I can’t answer that question. It’s a tenuous connection.”
- — Reginald Penner (2012), “Thermodynamics and Chemical Dynamics” 
- Lavoisier, Antoine; Laplace, Pierre. (1783). Memoir on Heat (translator: Henry Guerlac). Neale, 1982.
- (a) Wells, Herbert. (1906). "Lord of the Dynamos" (txt), in: The Door in the Wall, and Other Stories, Lord of the Dynamos (§7: The Daily Chronicle), Summer No. July 14th.
(b) Gaither, Carl C. and Cavazos-Gaither, Alma E. (2002). Chemically Speaking: a Dictionary of Quotations (pg. 125). CRC Press.
- Penner, Reginald. (2012). “Thermodynamics and Chemical Dynamics” (Ѻ), UCI Chem 131 C, May 7
- Carnot cycle – Hmolpedia 2020.