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Scheele, Carl Wilhelm

chemical acids oxygen time

[ shee luh] (1742–86) Swedish chemist: a discoverer of chemical elements (chlorine, and oxygen) and of many chemical compounds.

Scheele was trained as an apothecary, at a time when they made most of their own drugs and had available a range of minerals, plants and simple equipment for chemical operations. He had a passion for chemical experimentation which is probably unsurpassed, but he was unlucky in that some of his major discoveries were also made by others at nearly the same time and they published sooner. Nevertheless his renown led to prestigious job offers, which he refused, preferring to take a series of posts as an assistant apothecary. This left him able to experiment freely in his limited leisure time but the overwork, the poor conditions and the absorption of hazardous chemicals may have led to his early death.

Scheele first made the reactive green gas chlorine in 1774 from hydrochloric acid and MnO2 , but the fact that it is an element became known by work of 1810. Earlier, in 1773, Scheele had shown that air is a mixture (of ‘fire air’ and ‘foul air’ as he named its components) and he made oxygen in several different ways (e.g. by heating HgO, or KNO3 , or Hg(NO3 )2 ; or MnO2 with H2 SO4 ), but his book on this did not appear until 1777. Before then, in 1774, had published his discovery of oxygen. The two men were similar in their skill as experimenters, their limited interest in theory and their adherence to the phlogiston theory.

Scheele made a variety of new acids in the 1770s (phosphoric, molybdic, tungstic and arsenic acids) as well as HF, SiF4 , AsH3 and other reactive and very   toxic compounds. In the 1780s he made a number of new organic acids, and fairly pure hydrocyanic acid (recording its taste!). His death at 43 is unsurprising; he was a fanatical, prolific and probably unwise chemical discoverer.

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