6 On ihe various Comhinaiions of Carbon with Oxigett, 



of moiftened charcoal being introduced Into a coated glafs retort, heat was applied, and 



" gradually increafed until the retort became red. The firft portions of gas colle£led con- 



■^ifted of nine parts of carbonic acid gas, and 57 hydrocarbonate ; what came over about the 



middle of the procefs was three parts of carbonic acid, with 55 hydrocarbonate, and the 



laft portions were nearly pure hydrocarbonate, the whole amounting to feveral gallons. 



Having feparated the carbonic acid from this gas by repeated agitation with lime water, 

 I found that it was fpecifically lighter than common air, in the proportion of 1 1 to 23 ; in 

 this refpe£l, therefore, it differs eflentially from the gafeous oxides, being not more than 

 half their weight •, I likewife found, that when burned in a receiver containing pure or 

 common air, a very confiderable quantity of water was produced, and condenfed againft 

 the fides of the vefTel ; the receiver likewife contained much carbonic acid gas. I next 

 endeavoured to afcertain the proportion of oxygenous 'gas neceflary to faturate it. After 

 feveral trials I found, when fix meafures of this gas well waflied, were mixed with four of 

 pure oxygen, dnd exploded over mercury by the eleftric fpark, that the refiduary gas 

 amounted to 2^ meafures nearly, which was entirely carbonic acid. Here again we find a 

 remarkable difference between this hydrocarbonate and the gafeous oxides, for fix mea- 

 fures of oxygenous gas produce only 2|- of carbonic acid, when combined with the former ; 

 whereas with the latter, the fame quantity would produce no lefs than 14 meafures of the 

 fame acid gas. The produ£tion of water from the two gafes is likewife very different, 

 being little or none from the oxides, but very copious from the hydrocarbonate. Being 

 defirous to afcertain if any of the known hydrocarbonates were fimilar in their properties 

 to the gafeous oxides, I made comparative experiments with mod of them, but there were 

 none which appeared to contain oxygen, at leaft in any quantity. The pureft hydrocar- 

 bonates are obtained from camphor, by making its vapour pafs through a red hot tube ; 

 from ether by the fame procefs ; from animal fubftanccs, and fome vegetables, by de- 

 ftruftive diftillation -, and where it was not cxpeded, from the gas of marlhes, for 1 had 

 always fuppofed that this gas was fimilar to that obtained from moiftened charcoal by dif* 

 tillation. All thefe pure hydrocarbcfnates have exa£lly the fame properties ; when well 

 freed from carbonic acid gas, they are lighter than common air in the proportion of 15.5 

 to 23.5, or 2 to 3 nearly ; two parts by meafure require no lefs than 34 of pure oxygen 

 to faturate them, the produdls being 2\ parts carbonic acid with fome water (fee the table) 

 One of their moft remarkable properties however, is, that when mixed with | their bulk 

 of pure oxygen, or thereabout, and fired in a jar by the eleftric fpark, inftead of a dimi- 

 nution, there is a confiderable increafe of volume, notwithftanding the produdion of car- 

 bonic acid. The following may be confidered as the mean refult of feveral experiments 

 made in this way. 



Six meafures of hydrocarbonate, mixed with 4^ of pure oxygen, were introduced ihto 



a ftrong glafs jar over mercury, being fired by the eledlric fpark, the mixture after the 



explofion, which was violent, was augmented to I2|- meafures, or there was an increafe 



of 2t meafures nearly. Lime water being admitted, it foon became turbid, and there was 



A an 



