248 PHILOSOPHICAL TRANSACTIONS. [ANNO 1782. 



effervescence; and, by this same inflammable air is the copper evidently reduced, ac- 

 quiring splendour, malleability, and every other metallic property. But if the solu- 

 tion of copper be not saturated with copper, a small quantity of inflammable air may 

 be caught, as the excess of acid will disengage more of it from the iron than the 

 calx of copper can take up. Inflammable air is then the principle that metallizes 

 metallic earth; and if metals contain only a specilic earth and phlogiston, in- 

 flammable air certainly contains nothing else but phlogiston. If iron and the 

 arsenical acid be digested together, no inflammable air is produced; but the 

 arsenical acid is, in great measure, converted into white arsenic, as Mr. Berg- 

 man has observed, and also Mr. Scheele; what reason can be assigned why inflam- 

 mable air is not produced by this as well as by all other acids; but that this 

 metallic acid received it, and was by it reduced to a semi-metallic form, as by 

 pure phlogiston ? Yet this acid produces inflammable air from zinc, because zinc 

 gives out more phlogiston than the regulus of arsenic can take up; but it attracts 

 and is metallized by a part of it, and it is only the excess that appears in the 

 form of inflammable air, as Mr. Scheele has remarked. This inflammable air 

 indeed is not pure, for it holds some of the regulus in solution; but this portion 

 of regulus does not enter into its composition, as is very evident. 



Thirdly, inflammable air is the substance which, with vitriolic acid, forms 

 sulphur, for it is the very substance which the vitriolic acid separates from 

 metals; and this substance, so separated, when in sufficient quantity, and in 

 proper circumstances, unites to it in such proportion as to form common sul- 

 phur. Thus sulphur is formed by distilling concentrated vitriolic acid with iron 

 or bismuth, or by distilling tartar vitriolate with regulus of antimony. It is this 

 also that diminishes respirable air, as Dr. Priestley has clearly shown in the 5th 

 vol. of his Observations, p. 84; for though in its complete aerial state, after it 

 has absorbed that large quantity of fire requisite to its aerial form, it difficultly 

 and slowly unites to respirable air in the heat of the atmosphere, their points of 

 contact through their difference of density being very small, and there being no 

 substance at hand to receive the large portion of elementary lire they both con- 

 tain, and of which they must lose a large proportion before they can combine 

 together; yet while inflammable air is, as Dr. Priestley elegantly expresses it, in 

 its nascent state, before it acquires its whole quantity of specific fire, respirable 

 air easily unites to it, and is diminished in proportion to its purity; but if to a mix- 

 ture of both, igneous particles of density sufficient to be visible be introduced, a de- 

 gree of heat is excited, which, as it rarefies the dephlogisticated part of respirable air 

 to a greater degree than it can inflammable air, brings both into nearer contact, 

 increases their attraction to each other, and both uniting give out their fire, or 

 in other words inflame, when in proper proportion to each other, without any 

 decomposition ol either, unless the loss of a gnat part ol their specific fire be 



