m.) 



Jta. HENRY OH COMBUSTIBLE GASfiS, 



from carbonic 

 acid) is a teftof 

 its fitnefs to af- 

 ford light. 



fhattered with violence; and a V^olla's eudiometer, I of air 

 inch in thicknefs was burft by lefs than a cubic inch of a mix- 

 Specific gravity ti.ire of the two gafes. The fpecific gravity of the inflamma- 

 bL^gas"(trrer' ^'^ ^a^'es, when perfedly freed from carbonic acid, is another 

 conipetent left of their fitnefs as fources oF light. Thus the 

 fpecific gravity of the gas from moift charcoal, (common air 

 being 1000) according to Cruicktliank is 480; of the hydro- 

 carbjLiret from alcohol 520, and of the defiant gas, as deter- 

 mined by the Dutch chemifts, 909. 

 It is probable Ffom the limitation to the proportions^ in which bodies in 



mWe^'afe"s^arT S^'"^**^'* having a fufceptibility of chemical union, are capa- 

 mixtures of few ble of x'ombining, it feems to me reafonable to infer, that car- 

 finiple gafes. bpn and hydrogen do nut unite in all polfible proportions, form- 

 ing fo many diftincl compounds; but that the various inflam- 

 mable gafes are mixtures of a very few fimple ones. Of thofe 

 at prefent known, pure hydrogen gas; the carburetted hydro- 

 gen, which by combuftion affords an equal bulk of carbonic 

 acid, and confumes twice its bulk of oxigen; the carbonic 

 oxide; and the olefiant gas, it will appear, may be traced iw 

 the mixed gafes comprehended in the forgoing table. The 

 gas from coal I apprehend to be principally hydro-carburet, 

 with perhaps forae portion of carbonic oxide, the prefence of 

 which laft is rendered probable, becaufe the gas from coal is 

 faturated by lefs than twice its bulk of oxigen, though it gives 

 an equal volume of carbonic acid. Now the gas from marfhes, 

 which, with Mr. Cruickfhank, Mr. Dalton finds to be hydro- 

 carburet, contaminated with about 20 percent, azotic gas, con- 

 fumes, making allowance for this adulteration, double its vo- 

 lume of oxigen gas; and fince the gas from coal requires a lefs 

 proportion than this of oxigen, and yet gives an equal pro- 

 dud of carbonic acid with that from raarflies, it is fair to pre- 

 fume, tl>at it muft previoufly have contained fome oxigen, 

 which, after wafliing it with lime-water, can fubfifl in no 

 other (late than that of the carbonic oxide. 

 Gas from ignited The gas obtained by decompofing water over ignited char- 

 charcoal and (;.oa)^ is mofi probably a mixture of carbonic oxide with hydro- 

 wrbonic^oxide K^" g^''* ^"^ perhaps a little hydro-carburet. On no other 

 prefumption can the refults of its combufbon be explained ; 

 fince the quantity of oxigen required in faturating 100 meafures 

 fs only ten more than are confuraed by 100 meafures of pure 

 hydrogen, though 35 m. of carbonic acid, containing at leaft 



35 of 



Gas from coal 

 appears to be 

 hydro-carburet 

 with perhaps 

 fome carbonic 

 oxide. 



carbonic 

 with hydrogen 

 and a little hy- 

 <lro-carburct. 



