CLAIMS OF Lavoisier. ' ^33 



It is manifest, therefore, from the foregoing detail of facts, The discovery 

 that Rey first rightly attributed the weight acquired in the oxida- Jy Pev^^d^* 

 tion of metals to the attraction of air : that Mayow next sup- aftemards by 



Mayow, Hales, 

 and Bayen. 



Phlogistiqzi^, and contains a very elaborate examination of the facts 

 relating to sulphur and the metals, upon which that doctrine was 

 established. His second, On some Mercurial Precipitates, was pub- 

 lished in April following. The precipitate alluded to in the text, 

 was prepared with nitrous acid. In his third memoir, published in 

 the same work, for Feb. 1775, among other experiments, he states 

 the reduction of precipitate per se (or mercury oxidcil in the air), 

 and ^ays that the weight of the air he obtained from it was very 

 nearly the same as that lost by the reduction. He, therefore, doing 

 justice 1)1/ ref'ering to John Rc>j, ascribes the calcination to that air 

 having been absorbed. In the month preceding (viz. .Tan. 1775) 

 M. Bayen, with high commendation, gives an abstract, with the full 

 table of contents, of the work of John Rey, who was directed to the 

 facrof the increased weight of the oxide of tin by Brun, apotheca- 

 ry at Bergerac. 



M. Lavoisier's memoir, " On the nature of the principle whicli 

 " combinfts with metals during their calcination, and which aug- 

 " ments their weight," was read at the Royal Academy on the 26th 

 April, 1775, and was published in Rozier's Journal for May, in the 

 same year. In a note, the author says that the first experiments 

 relative to that memoir were made above a year earlier, and that - 

 those upon mercury precipitated per se were first tried by the 

 burning-glass, in November 1774, and afterwards made with all 

 the requisite precautions at the end of Feb. 1775. In the experi- 

 ment here related, the precipitate was reduced, by fire, in a closed 

 glass vessel ; and the properties of the air disengaged, are detailed 

 with perspicuity and conciseness. He considers it as more fit for 

 combustion, and more respirable than common air, of which he 

 takes it to be a part. 



It seems proper to remark in this place, that Dr. Priestley expel- 

 led air from precipitate per se by solar heat, Aug. 1, 1774, and was 

 extremely surprized at the vigorous combustion it produced :' that 

 in October following, being at Paris, he often mentioned his surprize 

 at this kind of air to M. Lavoisier, M. Le Roy, and other philoso- 

 phers in that city : and that this month immediately preceded the 

 very November in which M. Lavoisier informs us that the same ex- 

 periments were (Vahord tentees au verre ardent by himself, without 

 making tlie least mention of Priestley. See Priestley on Air, in 

 •3 volumes, vol. ii. p. 109, and Rozier's Journal before cited, v. 

 4o.9._w. N. 



Vol. XIV,— .July, 180(5. Hh ^ ported. 



