V 
OBSERVATIONS. 75 
contains fome arfenic, which is dio prov¬ 
ed by other experiments. It melts with 
the blow-pipe, and yields a fmoke of 
arfenic, and has the appearance of a 
fleel-grey cryftallized tcoria : on the con¬ 
trary, the acid of wolfram, of a yellow 
colour, prepared by digeftion in marine 
acid, is infufible with the blow-pipe, 
and thews no mark of arfenic, but the 
yellow changes into a bluifli colour. 
§ 6 
It is a peculiar property 
when melted with the microtofmic fait, 
or other falls containing thephofphoric 
acid in a proper proportioi, to give 
them a fine blue colour, jut it does 
not give a blue colour to borix. I made 
the two following experimtnts: 
(a) Prepared filex, . 
Calcined borax, of esch 2 drams. 
Acid 
