724 PHILOSOPHICAL TRANSACTIONS. [anNO l/QO. 



same air, which was placed in a tube inverted over mercury ; the water having a 

 stronger attraction to the marine acid than to the hepatic air. 



By the following experiment Dr. C. endeavoured to determine whether 

 vitriolic acid be produced by the combustion of hepatic with atmospherical air. 

 One measure of hepatic air, obtained from artificial pyrites, was mixed over 

 mercury with about 6 measures of atmospherical air, and fired by the electric 

 shock. A copious precipitation of sulphur took place, the remaining air was 

 then agitated with distilled water, the latter was filtered, and muriated barytes 

 was added, which produced a white precipitate not dissoluble in a large quantity 

 of water. From this, and the foregoing experiment it appears, that when sul- 

 phureous hepatic is burned with atmospheric air, a part of the sulphur is changed 

 into vitriolic acid, and the rest is precipitated ; but when it is burned with a suf- 

 ficient quantity of pure air, the sulphur is wholly converted into vitriolic acid. 

 Agreeably to this conclusion, the odour of the volatile vitriolic acid constantly 

 accompanies the combustion of hepatic with common air in open vessels ; and 

 when concentrated nitrous acid is added to water impregnated with hepatic air, 

 the filtered liquor becomes turbid on the addition of muriated barytes. 



The quantity of pure air required to saturate sulphureous hepatic air, does 

 not appear to correspond with the supposition that the last of these fluids con- 

 sists of sulphur dissolved in light inflammable air : for sulphur, in order to its 

 complete saturation, requires only 1 .43 times its weight of pure air ; but light 

 inflammable air requires for its saturation at least 6 times its weight of that fluid. 

 The specific gravity of hepatic air, as determined by Mr. Kirwan, is nearly equal 

 to that of pure air. If therefore ^ of the weight of hepatic consisted of light 

 inflammable air, that fluid would require for its saturation 2.26 times its bulk of 

 pure air : for the portion of it which consisted of light inflammable air would 

 require a quantity of pure air equal in bulk to the hepatic ; and the remaining 

 portion, consisting of sulphur, would require a quantity equal to 1.26 of the 

 hepatic. The entire quantity of pure air would therefore be to that of the he- 

 patic as 2.26 to 1 . If the hepatic contained -j-V of its weight of light inflamma- 

 ble air, it would require for its saturation 1.64 of its bulk of pure air. But 

 from the foregoing experiments it appears, that the quantity of pure air, neces- 

 sary to saturate 1 measure of hepatic air, is only 1.33 measures. Hence it is pro- 

 bable that this fluid does not consist of sulphur dissolved in light inflammable air. 



If we make allowance for the marine acid which was diffused through the 

 hepatic air, it will be found, that the quantity of pure air required to saturate it, 

 is nearly the same with that which would be required to change an equal weight 

 of sulphur into vitriolic acid. Whence it may be inferred, agreeably to the opi- 

 nion of Mr. Kirwan, that hepatic air is sulphur which has acquired an aerial 

 form by the application of heat. This conclusion is, he thinks, confirmed by 



