[ 402 ] [Book V. 



CHAP. VII. 



Of HEPATIC GAS. 



Mature of this Gas. Means of producing it. Its Properties. A chief 

 Conftituent of Sulphureous Mineral Waters. Turns Metals black. 

 Hoiv decompofea 1 , &c. 



MGengembre, who has made an analyfis of this 

 kind of air, regards it as a combination of pure 

 hydrogen and fulphur. The moft proper method of 

 obtaining it is by pouring marine acid on liver of 

 fulphur *, which extricates it in confiderable quantities. 

 It is equally produced from all livers of fulphur, whe- 

 ther they are made with alkalis or earths. By various 

 experiments, however, it now feems to be afcertained, 

 that as hepatic gas is compofed of fulphur and hydro- 

 gen in certain proportions, it cannot be produced ex- 

 cept water is prefent, the decompofition of which af- 

 fords the hydrogen. Thus, if marine acid air is ap- 

 plied to very dry liver of fulphur, fcarcely any hepatic 

 gas is produced, from the defecl of humidity. Liver 

 of fulphur, when heated, affords hepatic gas with the 

 addition of mere water without acid. In this cafe alfo 

 the water is decompofed -, its hydrogen unites with part 

 of the fulphur to form hepatic gas, while the oxygen 

 of the water uniting with another part, produces vi- 

 triolic acid, and this with the alkali forms a neutral fait 

 which will be defcribed in treating of vitriolic falts. 



A fubltance ufually formed frojn fixed alkali, or fait of tartar, 

 ind fulphur, combined by heat. . 



Ift. He- 



