Swedish chemist Scheele was a passionate chemical scientist who discovered oxygen and chlorine ahead of the actual discoverers given credit. He also demonstrated the effect of light on silver salts, significant to photography.
Early Years of Karl Wilhelm Scheele
Karl (Carl) Wilhelm Scheele was a German-Swedish, born on December 9, 1742, in Stralsund, Western Pomerania, Germany, at the time under Swedish rule. Instead of becoming a carpenter like his father, Scheele decided to become a pharmacist. He began as an apprentice at an apothecary in Gothenburg at the age of 14. He then worked as a pharmacist in Stockholm, from 1770-1775 in Uppsala, and later in Köping. In 1776, he was able to establish his own pharmacy.
Scheele's achievements are remarkable because he did not benefit from good education having come from a poor family. Throughout his life, he conducted most of his experiments limited from laboratory space and apparatus. After 1775, he moved to Köping to run a pharmacy where he remained. It was also during this year that he was elected to the Stockholm royal Academy of Sciences, a recognition that brought prestige and great job offers, but he chose to remain in Köping.
Scheele's Oxygen before Priestley
In 1772 Scheele's scientific efforts resulted in his most significant achievement, the discovery of oxygen, two years before Priestley. He made his "fire air" from a variety of sources and experiments, including the heating of compounds such as mercury oxide, nitric acid and potassium nitrate. He set his discovery into a more general theory of the atmosphere and combustion, and concluded that the former was composed of only two gases. The first, nitrogen ('vitiated air'), suppressed combustion; the other, 'fire air,' facilitated it.
Like Joseph Priestley, Scheele interpreted his work on oxygen only within the boundaries of the 'phlogiston' theory in his day. Unlike Priestley, he did not get credit for not publishing his findings until 1777, in his only text Chemical Observations and Experiments in Air and Fire. At this point, Priestley was already known as the discoverer of 'dephlogisticated' air.
Discovery of Chlorine, the Green Gas
Scheele isolated the greenish-yellowish gas in 1774 by treating a powdered black oxide of manganese and hydrochloric acid. Like oxygen, it was not until work by others in the early years of the 19th century that it was found to be an element discovered in his own right. The true nature of the chemical element was recognized in 1810 by English chemist Humphry Davy, who named it chlorine, and provided an explanation for its bleaching action.
Other Works and Discoveries by Scheele
From 1770 onwards, Scheele identified a number of chemical substances, including manganese dioxide, silicon tetrafluoride, barium oxide, copper arsenite, glycerol and hydrogen fluoride, sulphide and cyanide. He also recognized an array of new acids including arsenic, citric, hydrocyanic, prussic tartaric and tungstic varieties.
The Ardent Scientist
He died on May 21, 1786, at the age of 43. It is highly likely that the toxicity of many of the chemicals he was working with and the processes of identifying them, including smell and taste perhaps, might have contributed to his early demise.
Karl Scheele has also been credited with demonstrating the effect that light has on silver salts, later accepted as a basis for photography.
Sources:
Chambers Biographical Dictionary, edited by Una McGovern, Chambers, 2002
Quantum Leaps by Jon Balchin, Capella, London, 2004
Who Discovered What When by David Ellyard, New Holland, 2005
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