56 l-HILOSOPHICAL TRANSACTIONS. [aNNO 1791. 



inflammable air; since this would only prove, that phlogiston is one constituent 

 part of water; which is an opinion that I have advanced, and mentioned on se- 

 veral occasions; and it is the less extraordinary, as water resembles metals in the 

 remarkable property of being a pretty good conductor of electricity. What I 

 shall now allege however will make it very doubtful, whether pure water be ever 

 formed by the union of dephlogisticated and inflammable air; and perhaps make 

 it more probable that water, as I have lately advanced, is only the basis of those 

 kinds of air, as well as of every other kind. 



It was objected to my former experiments on the decomposition of dephlogisti- 

 cated and inflammable air, by firing them together in a copper vessel, which al- 

 ways produced an acid liquor, that this acid came from the phlogisticated air with 

 which the dephlogisticated air that I made use of was necessarily more or less di- 

 luted; or from that which I could not wholly exclude, as a part of atmospherical 

 air, when I exhausted the copper vessel by means of an air-pump. To obviate 

 this objection, I then observed, that I not only constantly found that the more 

 phlogisticated air was contained in the 2 other kinds of air (mixed in the pro- 

 portion of 2 measures of inflammable air to 1 of dephlogisticated) the less acid 

 I got; but that, when I purposely mixed any given quantity of phlogisticated air 

 with them, it appeared not to have been at all affected by the process, but re- 

 mained the very same, in quantity and quality, as before. Still however, because 

 Mr. Cavendish, though in a very different process, had found nitrous acid to 

 result from the decomposition of phlogisticated and dephlogisticated air; and 

 because M. Lavoisier and his friends had found nothing but pure water after the 

 slow burning of dephlogisticated and inflammable air; it was maintained by the 

 favourers of their system, that the water only in the liquor which I procured 

 came from the union of the 2 kinds of air, and the acid from the phlogisticated 

 air which I had not been able to exclude. 



But let any person only consider the very small quantity of nitrous acid which 

 was procured by Mr. Cavendish from the certain decomposition of SlQl grain 

 measures of atmospherical air, amounting to more than 6i ounce measures in 

 one case, and of 2710 grain measures, amounting to 5-^ ounce measures in ano- 

 ther case (Phil. Trans, v. 78,) ^ of which was phlogisticated air; and the vastly 

 greater quantity which I procured (ibid. p. 324,) when it could not be proved, 

 that a particle of phlogisticated air was decomposed, and think whether it was at 

 all probable, that the acid came from this kind of air, and not from the union of 

 the dephlogisticated and inflammable air, which evidently disappeared in very great 

 quantities. This circumstance alone might have satisfied those who interest them- 

 selves in this question; but it does not seem to have been attended to. 



I have now however eft'cctually removed the objection above mentioned, by en- 

 tirely excluding all phlogisticated air from the process; the dephlogisticated air 



