[ ^'I ] 



Thirty grains, from which all the carbonate of lime and oxyd 

 of iron had been previoufly extraded, were dried in a clofe vefTel, 

 and in fuch a heat as feemed fufficient to expel the water, and 

 afterwards calcined. By the calcination the powder was rendered 

 white, and loft that proportion of its weight which I affign in the 

 refult of the analyfis to the carbon and bitumen. 



Still, however, it remained to determine in what ftate, whc 

 ther of carbon or of bitumen fingly, or whether of a mixture of 

 both, the inflammable colouring matter exifted in the mineral. 



On the fuppofition that it was merely carbon in a ftate of ex- 

 treme divifion, it was boiled (the lime, argiil and iron having been 

 previoufly feparated) in concentrated nitrous acid. By this treat- 

 ment the intenfity of the colour was fomewhat diminiflied, and a 

 fmall quantity of nitrous air was produced. 



The next attempt was to feparate the bitumen, fuppofing that 

 it contained any. — To efted this, a large quintity of the powdered 

 calp was boiled in cauftic pot-afll, filtered and edulcorated ; but 

 as the relidu'um on the filtre retained the original colour, it confe- 

 quently could not have been entirely produced by bituminous 

 itiatt'ei'. 



That it contained, however^ fome bitumen, feems pretty evi- 

 dent ; for, having evaporated the filtered folution to drynefs, and 



diflTolved 



