254 PHILOSOPHICAL TRANSACTIONS. [ANNO 1782. 



state, that in which it is combined with metallic earths, &c. I have already 

 distinguished eight intermediate states each differing from the other by the por- 

 tion of elementary fire they contain, this quantity being, as far as I can judge 

 directly, as the rarefaction of the phlogiston ; but these researches are foreign to 

 my present subject. I shall only remark, that phlogiston, in a state perhaps 100 

 times rarer than inflammable air, and consequently containing much more fire, 

 may possibly constitute the electric fluid. 



p. s. Since the above was written, I have been honoured with a letter from 

 Dr. Priestley, in which he informs me, that he has reduced the calces of iron, 

 copper, lead, and tin, merely by melting them in inflammable air by means of a 

 burning glass. A certain quantity of inflammable air was absorbed by each 

 during their reduction ; but the unabsorbed part was equally inflammable, so 

 that there was no decomposition ; but the remainder was of the same nature as 

 the part absorbed. He also, by the same means, converted nitrous vapour into 

 nitrous air, and the phosphoric acid into phosphorus. And since the communi- 

 cation of the last-mentioned experiments, which seem to him also a direct proof 

 of the identity of inflammable air and phlogiston, he has been so obliging as to 

 inform me, that he has revived the calces of metals in* alkaline air as well as in 

 inflammable air, and also formed a phosphorus ; and that he has little doubt but 

 that he shall be able to produce any thing else in which phlogiston is supposed 

 to be concerned. This, he says, agrees with several of his former experiments, 

 especially that in which he produces inflammable air from alkaline air, by means 

 of the electric spark and volatile alkali from iron, supersaturated with phlogiston 

 by means of nitrous air, which he has repeatedly done since the publication of 

 his last volume. This observation, he adds, may help to explain some things in 

 the theory of chemistry, especially the affinity which all acids have both with 

 phlogiston and with alkalis ; but, he says, that alkaline air contains something 

 else besides phlogiston ; because when this air is used, there is always a residuum 

 of something that is neither alkaline nor inflammable air ; but he wants more 

 sun-shine to complete and extend his experiments on this subject.* 



Of the quantity of phlogiston in nitrous air. — 100 gr. of filings of iron being 

 dissolved in a sufficient quantity of very dilute vitriolic acid, produced, with the 

 assistance of heat gradually applied, 155 cubic inches of inflammable air, the 

 barometer at 29.5, and the thermometer between 50 and 6o°. Now inflam- 

 mable air and phlogiston being the same thing, this quantity of inflammable 

 air amounts to 5.42 gr. of phlogiston. 



Again, 100 gr. of iron, dissolved in dephlogisticated nitrous acid, in a heat 



* Since this paper was committed to the press, I find that Mr. l'ellctier has reduced the arsenical 

 acid to a regulus, by merely passing inflammable air through the solution of thai acid in twice its 

 weight of water. Roz. Journ. February 1762. — Orig. 



