The Phlogiston Theory

Stahl subsequently renamed the terra pingnis phlogiston, the motion of fire (or heat), the essential element of all combnstible materials. Thns the phlogiston theory was born to explain all combnstion and was widely accepted for most of the eighteenth centnry by, among others, such luminaries of chemistry as Joseph Priestley. 

In 1783 Lavoisier annonnced a basic reevalnation of the chemical theory, rejecting the phlogiston theory completely. At the same time, he elevated oxygen to a general explanatory principle (in a manner... 

In the days of alchemy and the phlogiston theory, no system of nomenclature that would be considered logical ia the 1990s was possible. Names were not based on composition, but on historical association, eg, Glauber s salt for sodium sulfate decahydrate and Epsom salt for magnesium sulfate physical characteristics, eg, spirit of wiae for ethanol, oil of vitriol for sulfuric acid, butter of antimony for antimony trichloride, Hver of sulfur for potassium sulfide, and cream of tartar for potassium hydrogen tartrate or physiological behavior, eg, caustic soda for sodium hydroxide. Some of these common or trivial names persist, especially ia the nonchemical Hterature. Such names were a necessity at the time they were iatroduced because the concept of molecular stmcture had not been developed, and even elemental composition was incomplete or iadeterminate for many substances. 

A. L. Lavoisier recognized oxygen as an element, developed the modem theory of combustion, and demolished the phlogiston theory. 

The reasoning here is reminiscent of the negative mass that had to be postulated to support the phlogiston theory. 

See Jean-Baptiste Dumas, who argued that Lavoisier s experiment of 1772 led to the overthrow of the phlogiston theory and founded modem chemistry, in Legons sur la philosophic chimique (Paris Ebrard,... 

The phlogiston theory was mainly due to Georg Ernst Stahl (1660-1734), Becher (1635-1682) had attempted to revive the once universally accepted sulphur-mercury-salt theory of the alchemists in a somewhat modified form, by the assumption that all substances consist of three earths — the... 

In fact, this discovery, and the realisation of its significance by Lavoisier, led to the abandonment of the phlogiston theory and, with his other work, established the basis of modem chemistry. 

Engels compares the overturning of the phlogiston theory with Marx s discovery of surplus value. He writes ... 

Pierre Joseph Macquer (1718—84) was known as a pracdcal chemist (he supervised the royal porcelain factory, for instance). He wrote an influential dictionary (1766 revised in 1778), and he is best known for being a supporter of precisely the phlogiston theory that Lavoisier helped to overturn. 

No one had ever isolated phlogiston, and this hypothetical substance apparently behaved in a contradictory manner. Nevertheless, an incorrect theory was quickly accepted, because what chemistry desperately needed then was a theory that could be used to guide research. The phlogiston theory, as we shall see, performed this function admirably. 

A more nearly correct theory of calcination and combustion had been proposed in the previous century. In 1630 the Frenchman Jean Rey theorized that the weight increase during calcination came about because air was incorporated into the calx. However, by the time the phlogiston theory was proposed, Rey s idea had been forgotten. It... 

The scientific revolution that began when Lavoisier announced his new theory of combustion was far from over. Chemists stuck to the phlogiston theory and some of them continued to cling to the old four-element theory as well, objecting that Lavoisier hadn t really shown that water could be decomposed. The hydrogen, they said, could have come from the hot iron over which the steam had been passed. 

Georg Ernst Stahl, 1660-1734. German chemist, physician, and professor. Co-founder of the phlogiston theory of combustion. Author of Fundaments Chymiae Dogmabcae et Expenmen-talis. He distinguished between potash and soda and recognized that alum contains a peculiar earth different from all others. 

Johann Joachim Becher, 1635-1682. German chemist and physician. Founder of the phlogiston theory. His experiments on minerals are described in his Physica Subterranea. Stahl summarized his views on combustion in a book entitled "Specimen Becherianum, ... 

This was the death blow to the phlogiston theory (56). Although Lavoisier discovered no elements himself, he was the first to assert that... 

M. and Mme. Lavoisier. In 1777 Lavoisier gave quantitative proof of the incorrectness of the phlogiston theory. Shortly after Priestley and Scheele discovered oxygen, Lavoisier gave the true explanation of combustion and respiration Ber-thollet, Guyton de Morveau, Fourcroy, and Klaproth were among the first to accept the new views. See also ref. (60)... 

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