368 M.LavofJter. [Book V* 



French Academy, he was of opinion, that the air which 

 is abforbed by the calcination of metals is common air, 

 but that it is of the very pureil kind, and more com- 

 buftible and refpirable than that in which we exift. 



This opinion verges fo clofely upon the dephlogif- 

 ticated, vital, or empyreal air of Dr. Prieftley, that 

 were we not informed by good authority, that M. La- 

 voifier firft received from cur Englifh philofopher * 

 the hint of extracting air from mercurius calcinatus, 

 the circumftance would in fome meafure affcc~l the 

 priority of his claim to that great difcovery. Dr* 

 Prieftley confeffes, that accident, rather than a pre- 

 concerted plan, was his guide upon this occafion. He 

 had been employed in extracting air from differenc 

 fubftances, and in particular in the converfion of the 

 different acids into fluids permanency elaftic. Among 

 the fubftances from which he endeavoured to extract 

 air was calcined mercury, which afforded it in confi- 

 derable quantities ; and upon applying the different tefts, 

 he found this air of a purer nature than the common 

 atmofpheric air. The air which was produced from, 

 red precipitate was equally pure with that which was 

 afforded by the mercurius calcinatus per Je t A fimilar 

 product was procured from red and white lead, from a 

 variety of fubftances moiftened with fpirit of nitre ; 

 laftly, from common nitre itfelf, from fedative fait, and 

 Roman vitriol. I omit noticing a number of erroneous 

 opinions, which were ftarted in the infancy cf the 

 fcience, as my prefent bufinefs is only to trace- the flepa 

 by which our knowledge has been gradually improved 

 in this department of nature. 



Dr. Prieftley continued his experiments on inflam- 

 mable air, and found that all the metals which yield ic 



* PricRIcy on Air, voh ii. p. 36, and 320. 



when 



