In 1703, Georg Stahl, building on the "oak tree burning experiment" of Johann Helmont (c.1620) and "three earths principle" of Johann Becher (1669), who theorized that earth was made of three principles, firstly: “terra pinguis”, a fatty, oily material substance, which gave things the property of combustion, and second: "terra lapidist", lastly: "terra fluida", theorized that when a metal burns it transforms into "calx" and what he called "phlogiston" as follows:
where "phlogiston", from the Greek phlogios, meaning ‘fiery’, both phi- rooted words, was Becher's terra pinguis, reformulated.
- Leicester, Henry; Klickstein, Herbert. (1951). A Source Book in Chemistry, 1400-1900 (§:Johann Becher, pgs. 55-58). Harvard.
- Higgins, William. (1789). A Comparative View: of Phlogistic and Antiphlogistic Theories. Murray, 1791.
- Phlogiston – Hmolpedia 2020.