ON ARSENIC 123 



long unchanged, and consequently acts longer upon metals, 

 I rather chose to conduct my experiments in the latter way. 



In long-necked flasks I added four parts of the acid of 

 arsenic to one part of filings of metals. After the water was 

 evaporated, I poured fresh upon the mixture. This method 

 I pursued in all the following experiments. 



SECTION XXII. UPON GOLD. 



(a) The acid of arsenic has no effect upon gold in the 

 heat of digestion. I put the mass into a retort, and 

 abstracted all the liquid, then increased the heat till the 

 acid flowed, and continued the same degree of heat for half 

 an hour, during which time a small quantity of arsenic was 

 sublimed. When the retort was grown cool, I poured a little 

 water into it, and placed it in sand. The acid was dissolved ; 

 but the remaining gold, being washed and dried, was found 

 to be nearly of the same weight as at first. The retort was 

 marked with red and yellow spots, which could not be taken 

 off by any menstruum, (b) The solution of gold was mixed 

 with acid of arsenic, but no precipitation ensued ; the mass 

 was then abstracted in a retort to dryness, and the fire 

 increased till it was in a perfectly fluid state ; the gold was 

 reduced, and some dephlogisticated muriatic acid came over 

 into the receiver. The retort was spotted red and yellow, 

 (c) The mixture of acid of arsenic and muriatic acid has no 

 effect upon gold, neither has a mixture of acid of arsenic and 

 nitrous acid. 



SECTION XXIII. UPON PLATINA. 



(a) Platina digested in the acid of arsenic is not attacked. 

 After all the humidity was abstracted, I increased the fire 



