The theory of phlogiston Carl Wilhelm Scheele

d. königl. schwed. acad. d. wissenschaft mitgliedes, chemische abhandlung von der luft und dem feuer (1777)

scheele achieved astonishingly prolific , important results without expensive laboratory equipment parisian contemporary antoine-laurent lavoisier accustomed. through studies of lavoisier, joseph priestley, scheele, , others, chemistry made standardized field consistent procedures. although scheele unable grasp significance of discovery of substance lavoisier later named oxygen, work essential abandonment of long-held theory of phlogiston.

scheele s study of gas not yet named oxygen prompted complaint torbern olof bergman, professor @ upsala university become scheele s friend. bergman informed scheele saltpeter had purchased scheele s employer, after long heating, produced red vapors (now known nitrogen dioxide) when came contact acetic acid. scheele s quick explanation saltpeter had absorbed phlogiston heat (had been reduced nitrite, in modern terms) , gave off new phlogisticated gas active principle when combined acid (even weak acid).

bergman next suggested scheele analyze properties of manganese dioxide. through studies of manganese dioxide scheele developed concept of fire air (his name oxygen). obtained oxygen heating mercuric oxide, silver carbonate, magnesium nitrate, , other nitrate salts. scheele wrote findings lavoisier able see significance of results. discovery of oxygen (ca. 1771) chronologically earlier corresponding work of priestley , lavoisier, did not publish discovery until 1777, after both of rivals had published.

although scheele believe in form of phlogiston theory, work reduced phlogiston unusually simple form, complicated fact chemists of scheele s day still believed light , heat elements , found in combination them. thus, scheele assumed hydrogen composed of phlogiston (a reducing principle lost when objects burned) plus heat. scheele speculated fire air or oxygen (which found active part of air, estimating compose 1 quarter of air) combined phlogiston in objects produce either light or heat (light , heat presumed composed of differing proportions of phlogiston , oxygen).

when other chemists later showed water produced when burning hydrogen , rusting of metals added weight them , passing water on hot iron gave hydrogen, scheele modified theory suggest oxygen salt (or saline principle of water), , when added iron, water reproduced, added weight iron rust.

pyrolusite or mno2.