Joseph Black
Scottish chemist, physicist, physician
April 16, 1728 - December 6, 1799

Joseph Black was a Scottish chemist, physicist, and physician, as well as a professor of chemistry at the University of Glasgow. His investigations of magnesium carbonate, magnesium oxide, and CO2, did much to overthrow the phlogiston theory. In 1755, Black proved that when limestone (CaCO‹) and other metal carbonates are heated to form metal oxides, they lose weight due to the escape of what he called "fixed air" (carbon dioxide, CO2). He also performed experiments proving that magnesia is entirely different from lime. His experiments were described in his paper, "Experiments upon Magnesia Alba, Quick-lime, and some other Alkaline Substances."

He also studied the phenomenon of heat and was the first to recognize that the quantity of heat was not the same as its intensity. This evolved into the theory of latent heat (1762) which later led his student Watt to invent the steam engine.