VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 480 



bottle with some water, and shaking it frequently ; whereas that used in the 

 preceding experiment had never passed through water, except in preparing it. 

 The condensed liquor was still acid. The experiment was also repeated with 

 dephlogisticated air, procured from red lead by means of oil of vitriol ; the 

 liquor condensed was acid, but by an accident I was prevented from determining 

 the nature of the acid. I also procured some dephlogisticated air from the leaves 

 of plants, in the manner of Doctors Ingenhousz and Priestley, and exploded it 

 with inflammable air as before ; the condensed liquor still continued acid, and of 

 the nitrous kind. 



In all these experiments the proportion of inflammable air was such, that the 

 burnt air was not much dephlogisticated ; and it was observed that the less phlo- 

 gisticated it was, the more acid was the condensed liquor. I therefore made 

 another experiment, with some more of the same air from plants, in which the 

 proportion of inflammable air was greater, so that the burnt air was almost com- 

 pletely phlogisticated, its standard being -J^. The condensed liquor was then 

 not at all acid, but seemed pure water : so that it appears, that with this kind 

 of dephlogisticated air, the condensed liquor is not at all acid, when the two 

 airs are mixed in such a proportion that the burnt air is almost completely phlo- 

 gisticated, but is considerably so when it is not much phlogisticated. 



In order to see whether the same thing would obtain with air procured from 

 red precipitate, I made two more experiments with that kind of air, the air in 

 both being taken from the same bottle, and the experiment tried in the same 

 manner, except that the proportions of inflammable air were different. In the 1st, 

 in which the burnt air was almost completely phlogisticated, the condensed liquor 

 was not at all acid. In the second, in which its standard was 1.86, that is, not 

 much phlogisticated, it was considerably acid ; so that with this air, as well as 

 with that from plants, the condensed liquor contains, or is entirely free from, 

 acid, according as the burnt air is less or more phlogisticated ; and there can be 

 little doubt but that the same rule obtains with any other kind of dephlogisti- 

 cated air. 



In order to see whether the acid, formed by the explosion of dephlogisticated 

 air obtained by means of the vitriolic acid, would also be of the nitrous kind, I 

 procured some air from turbith mineral, and exploded it with inflammable air, the 

 proportion being such that the burnt air was not much phlogisticated. The con- 

 densed liquor manifested an acidity, which appeared, by saturation with a solution 

 of salt of tartar, to be of the nitrous kind ; and it was found, by the addition of 

 some terra ponderosa salita, to contain little or no vitriolic acid. 



When inflammable air was exploded with common air, in such a proportion 

 that the standard of the burnt air was about -f^, the condensed liquor was not in 

 the least acid. There is no difference however in this respect, between common 



VOL. XV. 3 R 



