c m 3 



on account of it's being inflammable ; hence it is 

 called inflammable air. See §. V. page 



b. Sulphurated Hydrogen, Hepatic Gas, is ob- 

 tained from livers of fulphur, or fulphures, by de- 

 compofing them with acids. Sulphur combines 

 with hydrogen gas, called fulphuret, or hydrogen 

 gas, or fulphurated hydrogen gas, or hepatic air. 



II. Simple bituminous Substances. 



Bituminous fub fiances are not of mineral ori- 

 gin, but have been formed from certain prin- 

 ciples of fubftances belonging to the organifed 

 kingdoms of nature ; which, after the lofs of ani- 

 mal and vegetable life, have fufFered consider- 

 able changes, by long contact and union with mi- 

 neral bodies ; and may hence be regarded as 

 forming a part of the mineral fyftem. 



a. Naptha, is a light, thin, often colourlefs 

 oil, highly odoriferous and inflammable, which in 

 fome parts of Perfia and Italy is found upon the 

 furface of fprings and lakes, and iffuing from ar- 

 gillaceous ftones ; does not combine with water 

 or fpirit of wine; when burned, leaves a black 

 foot; acids condenfe it and render it refinous: 

 when firft expofed to the air, it becomes yellow ; 

 afterwards, and in like proportion, it thickens, and 

 palfes into 



b. Petroleum, or Rock Oil; and feems chiefly 

 to differ from Naptha in being mixed with hete- 

 rogeneous 



