1742-1786

Swedish chemist who made many contributions to chemistry, including the discovery of oxygen. He probably prepared oxygen, which he called "fire-air," as early as 1772, two years before Joseph Priestley. Scheele, however, published little and his work was not as well known. Scheele's book Chemical Observations and Experiments on Air and Fire (1777) presented evidence that the atmosphere is composed of two gases, one of which prevented combustion and another that supported combustion. Other substances discovered by Scheele include tartaric acid, arsenic acid, lactic acid, citric acid, oxalic acid, tungstic acid, and hydrocyanic acid.