Mercurius calcinatus

On the r of August, 1774,1 endeavoured to extract air from mercurius calcinatus per se and I presently found that, by means of the lens, aif was expelled from it very readily. . . But what surprised me more than I can well express, was, that a candle burned in this air with a remarkably vigorous flame. . . ... 

In this paper Lavoisier describes a further experiment with mercuric oxide, first reducing it with charcoal and collecting the gas evolved which proved to be fixed air. By this procedure, since they behave in this way, he had established that mercurius calcinatus a true metallic calx. Doubts that it was a true metallic calx arose from two facts, that mercury itself was a liquid, unlike any other metal, and that almost alone among metals, its calx could be reduced to mercury metal by heat alone, without charcoal. 

Priestley, after his return from the continent in November, 1774, did not take up the more extensive study of the new gas he had obtained from mercurius calcinatus until May 1, 1775. He then found that when tested for purity by his usual test, the nitrous air, that the new gas was much purer than common air, even between five and six times as good as the best common air that I have ever met with. Being now fully satisfied with respect to the nature of this new species of air, viz., that, being capable of taking-more phlogiston from nitrous air, it therefore contains loss... 

Sidney J. French, The Chemical Revolution— The Second Phase, Journal of Chemical Education 27, 1950, 83-89 Guerlac, Antoine-Laurent Lavoisier Perrin, Prelude to Lavoisier s Theory of Calcination Some Observations on mercurius calcinatus per se, Ambix 16, 1969, 140-151 Holmes, Lavoisier, 41-48 Historians differ a great deal in judging the sequence of events here, but Holmes synthesizes various accounts convincingly. 

Perrin, Prelude to Lavoisier s Theory of Calcination Some Observations on Mercurius calcinatus perse, Ambix 16,1969,140-151, at 144-145 William... 

He therefore inferred, as I have said that I myself had once done, that this substance had, during the process of calcination, imbibed atmospherical air, not in part, but in whole. But then he extends his conclusion, and, as it appears to me, without any evidence, to all the metallic calces saying that, very probably, they would all of them yield only common air, if, like mercurius calcinatus, they could be reduced without addition. 

He [Lavoisier] is an Intendant of the Finances, and has much public business, but finds leisure for various philosophical pursuits, for which he is exceedingly well qualified. He ought to have acknowledged that my giving him an account of the air I had got from Mercurius Calcinatus, and buying a quantity of M. Cadet while I was in Paris, led him to try what air it yielded, which he did presently after I left. I have, however, barely hinted at this in my second volume. 

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