Scheele worked as a pharmacist in Stockholm, from 1770 to 1775 in Uppsala, and later in Köping. His studies led him to the discovery of oxygen and nitrogen in 1772-1773, which he published in his only book, Chemische Abhandlung von der Luft und dem Feuer (Chemical Treatise on Air and Fire) in 1777, losing some fame to Joseph Priestley, who independently discovered oxygen in 1774.
Scheele also discovered other chemical elements such as barium (1774), chlorine (1774), manganese (1774), molybdenum (1778), and tungsten (1781), as well as several chemical compounds, including citric acid, glycerol, hydrogen cyanide (also known as prussic acid), hydrogen fluoride, and hydrogen sulphide. In addition, he discovered a process similar to pasteurization.
Like many other chemists of his time, Scheele often worked under difficult and even dangerous conditions, which might explain his early death.