Combustion, doctrine

Though it should be easier for modern historians to maintain the distinction between utility and truth, it isn t always done. In particular, if we wish to understand the loyalty of the eighteenth-century chemists to the phlogiston doctrine, we must recognize that they accepted it as both useful and true, and indeed it was perhaps their recognition of its utility in providing organization for combustion and calcination that they confused with truth. 

Lavoisier s systematic use of the conservation of weight principle inverted the relative simplicities of the metals and their calxes, the combustibles and their products, a compositional reversal of such clarity that the new doctrine was universally called the anti-phlogistic chemistry. Fourcroy, the chief contemporary publicist for the chemical revolution, described its reception thus ... 

Helene Metzger, La Philosophic de la matiere chez Stahl et ses Disciples, Isis 8,1926, 427-464 idem, La Theorie de la composition des sels et la theorie de la combustion d apres Stahl et ses Disciples, Isis 9, 1927, 294-325 idem, Newton, Stahl, Boerhaave, et la Doctrine chimique (Paris Felix Alcan, 1930). 

Black correctly says that Lavoisier s theory that gases contain heat in combination is founded on the doctrine of latent heat, and is, indeed, an extension of it . Lavoisier s theory of combustion in oxygen is that the burning body collects, and condenses this sort of air, depriving it at once of its vaporous and elastic aerial form or, if it does not absolutely condense it to a solid matter, it diminishes, to a great degree, its capacity for heat. ... 

Most of the fire fixed in the bodies is in the pure air, which is the true combustible body, perhaps the only one in nature . The different phenomena of combustion and calcination are explained in a very happy [tres heureuse] manner by Stahl s hypothesis but there is no need to assume with Stahl that bodies which increase in weight lose part of their substance (the main difficulty in the phlogiston theory). Lavoisier does not claim to substitute for Stahl s doctrine a rigorously demonstrated theory but only a hypothesis which seems more probable, more conformable to the laws of nature, and contains less forced explanations and fewer contradictions . 

Recherches sur les Causes des principaux Faits physiques, et particulierement sur celles de la Combustion. . . , 2 vols., Paris, An II (1794) Refutation de la Theorie pneumatique, ou de la Nouvelle Doctrine des Chimistes Modemes. . . , Paris, An IV (1796). 

Nicholson pointed out that those who maintJlined the doctrine of phlogiston are at present returned to the old doctrine of sulphur and oils, though in more general terms , regarding phlogiston not as fixed fire but as some identical combustible principle which unites with respirable air and in doing so extricates heat. 

Priestley, 1796/1969] J. Priestley. Considerations on the Doctrine of Phlogiston, and the Decomposition of Water (and Two Lectures on Combustion, etc., by John MacLean) (New York Kraus Reprint Co.), 1969. This is a reprint of the original edition published in 1796 in Philadelphia by Thomas Dobson. 

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