Scheele, Karl Wilhelm (1742–1786)

Swedish chemist and pharmacist who isolated many elements and compounds for the first time, including oxygen, about 1772, and chlorine in 1774, although he did not recognize it as an element. He showed that oxygen is involved in the respiration of plants and fish.

In the book Abhandlung von der Luft und dem Feuer/Experiments on Air and Fire 1777, Scheele argued that the atmosphere was composed of two gases. One, which supported combustion (oxygen), he called ‘fire air’, and the other, which inhibited combustion (nitrogen), he called ‘vitiated air’. He thus anticipated Joseph Priestley's discovery of oxygen by two years.

Scheele was born in Stralsund, Pomerania (now in Germany). At 14 he became an apothecary's apprentice in Göteborg. Practising as an apothecary, he moved via Malmö to Stockholm and finally Uppsala in 1770, where his talents as a chemist were recognized. Although offered academic positions in Germany and England, from 1775 he ran a pharmacy in the small town of Köping on Lake Malären in Västmanland.

Scheele's discoveries include arsenic acid, benzoic acid, calcium tungstate (scheelite), citric acid, copper arsenite (Scheele's green), glycerol, hydrogen cyanide and hydrocyanic acid, hydrogen fluoride, hydrogen sulphide, lactic acid, malic acid, manganese, nitrogen, oxalic acid, permanganates, and uric acid. He also discovered that the action of light modifies certain silver salts (50 years before they were first used in photographic emulsions).