Scheele, Carl

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Scheele, Carl

SWEDISH CHEMIST
1742–1786

Carl Wilhelm Scheele was born in Pomerania (on the Baltic coast of northeastern Europe, then under Swedish control). As a young man Scheele worked as an apothecary and studied chemistry under the famous chemist Torbern Bergman. Bergman once called Scheele one of his greatest discoveries. Scheele's laboratory techniques in chemistry were so exacting that his work fostered advances in several areas of chemistry. Scheele's achievements in organic chemistry included the isolation of glycerin and twelve organic acids—among them tartaric, citric, oxalic, mucic, malic, lactic, uric, gallic, and tannic acids. Among the metals Scheele was the first to identify were barium, molybdenum, and tungsten. He was the first to isolate elemental phosphorus from bone. Scheele was the first to characterize plumbago (graphite) as a form of carbon. He was one of the discoverers of the adsorption of gases by "activated charcoal." In 1777 Scheele was the first to describe the reduction of silver salts to metallic silver via the action of sunlight (the basis of photography).

Scheele developed a general method for investigating organic acid. His first step was to precipitate the acid as a crystalline calcium salt. He would purify the salt and then decompose it using sulfuric acid. (Calcium sulfate precipitates out, leaving the free organic acid for characterization.) Another of Scheele's separation techniques was the precipitation of the lead salts of acids, which were generally less soluble than the calcium salts. The lead salts were also decomposed with sulfuric acid to produce the free organic acids.

His investigations of reactive gases and corrosive liquids included such compounds as ammonia, hydrogen chloride (the gaseous form of hydrochloric acid), hydrogen fluoride (which can dissolve glass), silicon fluoride (highly corrosive), hydrogen sulfide (the active ingredient of a stink bomb), hydrocyanic acid, and arsenic acid. He was the first to isolate chlorine gas, which became the basis of the bleaching industry.

Scheele is most often remembered as one of the discoverers of oxygen, along with Joseph Priestley and Antoine Lavoisier. Scheele's work on the gas he called "fire-air" was completed between 1770 and 1773. This predated the work of Lavoisier or Priestley. Scheele's Chemical Observations and Experiments on Air and Fire was not published until 1777, after the comparable findings of Lavoisier and Priestley had been reported. Like Priestley, Scheele retained use of the phlogiston theory in most of his chemical work. Unlike Priestley, Scheele died at a young age. He died at forty-three, at a time when Lavoisier was consolidating the chemical revolution.