S66 NATIVE ArsENIATE OF tEAc; 



eihployed a vessel with a long neck for the solution, arid 

 did not expose it to heat. 



I concluded therefore, that, when the process was con^ 

 ducted under different circumstances, the predominating 

 mass of nitric acid produced its eifeCt, and volatilized a 

 portion of the muriatic, 

 2nd source of Another source of errour 1 found in the following ano* 

 errour. malous circumstance, tiz. a simultaneous precipitation of a 



portion of arseniate of lead takes place with that of muriate 

 of silver. Whatever combination this may be, it is a weak 

 one, and may be severed by nitric acid, which dissolves the 

 arseniate and leaves the muriate; or by ammonia, which 

 takes up the muriate, to the exclusion of the arseniate. 



The conclusion, to which many experiments have led me, 

 is this, that the muriate of silver, produced in the nitric 

 solution of one hundred grains of arseniate of lead by 

 nitrate of silver, amounts to about 9*5. 

 Proof that the J], Ju order to prove, that the acid, which is combined with 

 mineral is the ^^6 oxide of lead in this mineral, is the arsenic acid, and 

 arsenic. that it is not combined with phosphoric, I decomposed some 



of its acid, which had been combined with lead in the fore- 

 going experiments, by means of sulphuric acid, and filtered 

 off the sulphate of lead. The fluid which passed through 

 the filter was evaporated nearly to dryness, and it assumed 

 the appearance of crystalline grains. Some of it was ex* 

 posed to the flame of the blowpipe in a gold spoon; at first 

 it became like a white dry powder, which melted before an 

 increased heat: placed on charcoal ^nd. ignited, it was to- 

 tally dissipated in arsenical fumes. 



Some of it was dissolved in water, and dropped into liquid 

 sulphate of titanium, a white precipitate was produced: 

 combined with soda, it precipitated silver from the nitrate 

 of silver, of a brick colour. It precipitated mercury from 

 its nitrate, of a yellowish colour, which afterward became 

 reddish. This precipitate, exposed to the flame of the blow- 

 pipe on charcoal, exhibited the same phenomena as arseniate 

 of mercury. 

 Fallacious I precipitated magnesia from its muriate, and redissolved 



mode of dis- jj. fey carbonate of ammonia, perfectly saturated with car- 



tmguishing •' / i j 



the phosphoric bonic acid. I divided this liquid into two portions, and 



dropped 



