VOL. LXXIV.] PHILOSOPHICAL TRANSACTIONS. 4gi 



so far was M. Lavoisier from thinking any such opinion warranted, that till he 

 was prevailed on to repeat the experiment himself, he found some difficulty in 

 believing that nearly the whole of the two airs could be converted into water. 

 It is remarkable, that neither of these gentlemen found any acid in the water 

 produced by the combustion ; which might proceed from the latter having burnt 

 the two airs in a different manner from what I did ; and from the former having 

 used a different kind of inflammable air, namely, that from charcoal, and perhaps 

 having used a greater proportion of it. 



Before entering into the cause of these phenomena, it will be proper to take 

 notice, that phlogisticated air appears to be nothing else than the nitrous acid 

 united to phlogiston ; for when nitre is deflagrated with charcoal, the acid is 

 almost entirely converted into this kind of air. That the acid is entirely con- 

 verted into air, appears from the common process for making what is called 

 clyssus of nitre ; for if the nitre and charcoal are dry, scarcely any thing is found 

 in the vessels prepared for condensing the fumes ; but if they are moist, a little 

 liquor is collected, which is nothing but the water contained in the materials, 

 impregnated with a little volatile alkali, proceeding in all probability from the 

 imperfectly burnt charcoal, and a little fixed alkali, consisting of some of the 

 alkalized nitre carried over by the heat and watery vapours. As far as I can per- 

 ceive too, at present, the air into which much the greatest part of the acid is 

 converted, differs in no respect from common air phlogisticated. A small part 

 of the acid however is turned into nitrous air, and the whole is mixed with a 

 good deal of fixed, and perhaps a little inflammable air, both proceeding from 

 the charcoal. 



It is well known, that the nitrous acid is also converted by phlogistication into 

 nitrous air, in which respect there seems a considerable analogy between that and 

 the vitriolic acid ; for this acid, when united to a smaller proportion of phlo- 

 giston, forms the volatile sulphureous acid and vitriolic acid air ; both of which, 

 by exposure to the atmosphere, lose their phlogiston, though not very fast, and 

 are turned back into vitriolic acid ; but, when united to a greater proportion of 

 phlogiston, it forms sulphur, which shows no signs of acidity ; unless a small 

 degree of affinity to alkalis can be called so, and in which the phlogiston is 

 more strongly adherent, so that it does not fly off when exposed to the air, unless 

 assisted by a heat sufficient to set it on fire. In like manner the nitrous acid 

 united to a certain quantity of phlogiston, forms nitrous fumes and nitrous air, 

 which readily quit their phlogiston to common air ; but when united to a dif- 

 ferent, in all probability a larger quantity, it forms phlogisticated air, which 

 shows no signs of acidity, and is still less disposed to part with its phlogiston 

 than sulphur. 



This being premised, there seem 1 ways by which the phenomena of the acid 



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