io8 CLASSICS OF MODERN SCIENCE 

 dephlogisticated air is converted into pure water. It is not easy, 

 indeed, to determine from these experiments what proportion the burnt 

 air, remaining after the explosions, bore to the dephlogisticated air 

 employed, as neither the small nor the large globe could be perfectly 

 exhausted of air, and there was no saying with exactness what 

 quantity was left in them ; but in most of them, after allowing for 

 this uncertainty, the true quantity of burnt air seemed not more than 

 1-17 of the dephlogisticated air employed, or 1-50 of the mixture. 

 It seems, however, unnecessary to determine this point exactly, as the 

 quantity is so small, that there can be little doubt but that it proceeds 

 only from the impurities mixed with the dephlogisticated and inflam- 

 mable air, and consequently that, if those airs could be obtained per- 

 fectly pure, the whole would be condensed. 



With respect to common air, and dephlogisticated air reduced by 

 the addition of phlogisticated air to the standard of common air, the 

 case is different ; as the liquor condensed in exploding them with in- 

 flammable air, I believe I may say in any proportion, is not at all acid ; 

 perhaps because if they are mixed in such a proportion as that the 

 burnt air is not much phlogisticated, the explosion is too weak, and 

 not accompanied with sufficient heat. 



All the foregoing experiments, on the explosion of inflammable air 

 with common and dephlogisticated airs, except those which relate to 

 the cause of the acid found in the water, were made in the summer of 

 the year 1781, and were mentioned by me to Dr. Priestley, who in 

 consequence of it made some experiments of the same kind, as he 

 relates in a paper printed in the preceding volume of the Transactions. 

 During the last summer also, a friend of mine gave some account of 

 them to M. Lavoisier, as well as of the conclusion drawn from them 

 that dephlogisticated air is only water deprived of phlogiston ; but at 

 that time so far was M. Lavoisier from thinking any such opinion 

 warranted, that, till he was prevailed upon 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 

 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. 



