VOL. LXXX.] PHILOSOPHICAL TKANSACTIONS. 637 



culiar substance which exists in all these states, whether that substance be called 

 charcoal, or the gravitating matter of heavy inflammable air. 



Hence it appears, that the phlogisticated and heavy inflammable airs com- 

 bined, constitute charcoal ; and that the mere application of heat always resolves 

 charcoal into these 2 substances. But the heavy inflammable air is itself a com- 

 pound of the lighter inflammable and phlogisticated airs. If phlogisticated air 

 be combined with the heavy inflammable, or, which is the same thing, if light 

 inflammable air be taken from it, charcoal is reproduced ; therefore, when sul- 

 phur is melted in the heavy inflammable air, and hepatic air formed in it, the 

 remaining parts of the heavy inflammable air return to the state of charcoal. 

 And lastly, when sulphur is melted in contact with charcoal, the decomposition 

 is complete ; and the charcoal is resolved into its ultimate particles, the phlogis- 

 ticated and light inflammable airs, with a small admixture of volatile alkali. 



Thus far he had proceeded in the decomposition of the heavy inflammable air. 

 The formation of this air, on many occasions, confirms what has been said con- 

 cerning its analysis. In the resolution of compound bodies into their constituent 

 parts, it may always be suspected, that the whole is not accounted for, that some 

 part may have eluded observation, till the very parts we assign are put together, 

 and the same compound is produced from them. The frequent production of 

 fixed air, from substances generally not supposed to contain the heavy inflamma- 

 ble air, has lately given rise to a new system in chemistry. The author of this 

 system has the merit of pointing out the appearance of fixed air in almost all 

 phlogistic processes, n the combustion of various substances, in the reduction 

 of metals, and in the decomposition of acids ; phenomena which cannot other- 

 wise be accounted for, than by showing that the specific matter of charcoal is a 

 compound body ; that its component parts are present in all these processes ; 

 and in some of them nothing else, if we except dephlogisticated air. 



Dr. A. has already taken notice of the formation of fixed air from nitrous am- 

 moniac, which is now well known to contain nothing but the phlogisticated, 

 light inflammable, and dephlogisticated airs. This salt, heated in close vessels, 

 yields dephlogisticated nitrous air in great abundance, mixed with a small pro- 

 portion of fixed air. He has often repeated this experiment with nitrous ammo- 

 niac, which indicated no trace of fixed air either with lime water, or with acids, 

 before its decomposition ; but, when the salt was decomposed by heat, he always 

 found lime-water rendered turbid by the generated air ; and, on adding an acid 

 to the turbid lime-water, has observed air-bubbles to be produced in it. When 

 the 3 elementary airs are in a condensed state, and are set free from any combi- 

 nations, they unite and form fixed air without the assistance of heat. Thus 

 fixed air is generally produced when metals are dissolved in the nitrous acid. In 

 these solutions, the component parts of nitrous acid and the light inflammable ' 



