Water Will Not Float Phlogiston

Ekiund, The Incompleat Chymist, Smithsonian Institution Press, Washington, D.C., 1975. 

We have imbibed, sweated, and excreted water since time immemorial—so it might be nice to know what it s made of. Water boils, freezes, and is recovered unchanged from salts and other earths. It is absolutely elemental to our very existence, as is air. One of the four Aristotelian elements, water can be transmuted to air by adding heat, to earth by removing wetness, and it neutralizes its contrary element—fire. Its status as an element survived Robert Boyle s scathing criticism of the ancients in his 1661 classic The Sceptical Chymist. As late as 1747, Ambrose Godfrey, Boyle s very capable assistant, reported the chemical conversion of water to earth, an experimental conclusion once and for all time refuted in 1770 by Antoine Lavoisier. So, when and how did we learn the true nature of water, or how to get From H to eau, as Philip Ball so wittily phrases it  

FIGURE 205. Fig. 5 shows the apparatus for s) nt iesis of water from hydrogen and oxygen. Once the correct amounts are added, a spark is set off at L and quantitative reaction occurs. (From Lavoisier, Traite Elementaire de Chimie, seconde edition, 1793.) 

FIGURE 206. From Lavoisier s Elements, an apparatus for collection gases from fermentations. 

Lavoisier did not invent the law of conservation of matter. It was a firm assumption in the minds of contemporary and earlier scientists. However, his careful trapping of gases in preweighed liquids and his requirement that all matter in a chemical reaction must be accounted for brought chemistry to a new level as a science—some even called it physics. If the mass at the start of a reaction and at the end could not be matched then there was not much point in analyzing the chemistry. It was as if the Ferme Generale were conducting an audit. 

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