[ ‘964. JJ 
Of Vitriol of Iron. 
250 ers. of cryftallized vitriol of iron expofed to a fand heat 
of 420° became of a dirty white colour, and loft 98 grs. of its 
weight, that is 39 per cent. 
480 grs. of the cryftallized vitriol of iron diftilled in a fand 
heat of 460° became grey and loft rg1 grs. of water flightly 
acid, that is 40 per cent. 
Hence I conclude that 100 parts vitriol of iton contain 39 of 
water of cryftallization, the acidity indicates about 1 gr. of 
acid. 
-T ruen diffolved too grs. of the cryftallized falt in 3 ounces 
of water, and gradually added to it the teft alkali, the fame I 
ufed in the decompofition of allum. In the temperature of 60° 
there was no effervefcence, though a greyifh precipitate appeared ;) 
but when the folution felt a heat of 120° a flight quantity of 
air was’ difengaged, which increafed as the heat approached to 
that of boiling, fo that here alfo a compound falt was formed. 
I conftantly afterwards made the folution boil.as long as any pre- 
cipitate appeared, and thus found that 133 grs. of the alkaline 
folution were neceflary to precipitate the whole of the iron, that 
is 31,75 grs. of mere alkali, which indicates the prefence of 
26,13 of the ftrongeft acid or 29,21 of ftandard. 
Tue 
