'252 l'HILOSOPHICAL TKANSACTIONS. [ANNO 1J62. 



sealed and heated till the glass was softened, stained the glass black, and the tube 

 being opened, the air was found reduced to ■£• of its bulk. ; and this residuum was 

 found to be mere phlogisticated air, neither precipitating lime-water, nor being 

 affected by nitrous air, or in the least inflammable. Yet decisive as this experi- 

 ment appears, a little consideration will show the absolute impossibility that in- 

 flammable air should consist of ^ phlogisticated air and §■ phlogiston ; for, in 

 the first place, one cubic inch of phlogisticated air weighs 0.377 of a grain: 

 now let us suppose, that to this phlogisticated air is added ■§. of its bulk of phlo- 

 giston ; and to make the supposition still stronger, let us also suppose that 

 phlogiston has no weight ; then, by the supposition, this compound of phlogis- 

 ticated air and phlogiston will constitute inflammable air, and amount to a bulk 

 of 3 cubic inches, and these 3 cubic inches will weigh no more than 0.377 of a 

 grain ; but if 3 cubic inches of inflammable air weigh 0.377 of a grain, 1 cubic 

 inch should weigh 0.105 of a grain, which cannot be ; for then inflammable air 

 would be little more than -i- lighter than common air, contrary to all the experi- 

 ments that have been hitherto made, and particularly those of Mr. Cavendish, 

 Fontana, and Dr. Priestley himself, which show it to be about 1 1 times lighter 

 than common air. Secondly, it is said, that the matter which stained the glass 

 black was the true phlogistic part of inflammable air, and was afterwards sepa- 

 rated by means of minium. This then contained no phlogisticated air ; but is 

 it not certain, that if there had been enough of it, the minium would have been 

 reduced and converted into lead ? And might not inflammable air be again se- 

 parated from that lead, though no phlogisticated or common air were at hand to 

 supply its other supposed constituent part ? Thirdly, in one of Dr. Priestley's 

 experiments the inflammable air, contained in the glass tube which was most 

 heated, was reduced to so small a bubble, that no experiment could be made on 

 it : therefore, in this, at least, the quantity of phlogisticated air did not amount 

 to J-, but was quite inconsiderable ; the remainder then, being taken up by the 

 calx of lead in the glass, was pure mere phlogiston ; so that this experiment is a 

 strong proof of my opinion. Fourthly, if phlogiston could be decomposed by 

 heat, and then leave a residuum of phlogisticated air, amounting to -l of its 

 bulk, the diminution arising from its inflammation with common or dephlogisti- 

 cated air could never be so great as it is found to be by repeated experiments; 

 for when inflammable and common air are fired in the proportion of 1 1 of the 

 latter to 4 of the former, a bulk equal to the whole of the inflammable air, and 

 to J- of the common air, disappears, according to Mr. Volta, and the diminu- 

 tion is about 4 of the whole, or more exactly out of 15 measures, only 8.8 

 remain ; but if the inflammable air were decomposed, and £ of it, being phlo- 

 gisticated air, should remain, then not quite J- the whole would vanish, and the 

 residuum should be 10.54 measures. This evidently proves, that pure inflam- 



