In chemistry, terra pinguis was considered as the fatty, oily material substance of bodies that gives things the property of combustion. [1]
In 1669, German physician and chemist Johann Becher introduced the term "terra pinguis", conceived as an updated version of Paracelsus’ 1524 sulphur model of how things burned.
In 1703, Becher’s student Georg Stahl updated the terra pinguis model of with a phlogiston model of combustion. [2] This in turn gave way to the caloric theory by French chemist Antoine Lavoisier in circa 1780; which culminated in the mathematical entropy concept developed by German physicist Rudolf Clausius in 1865.
References
1. Partington, J.R. (1957). A Short History of Chemistry (terra pinguis, pgs. 86, 148). MacMillan and Co.
2. Leicester, Henry M. and Klickstein, Herbert S. (1969). A Source Book in Chemistry, 1400-1900 (pg. 58). Harvard University Press.
