C. E. Avery on the Nitrate of Silver Test. 257 
the reagents so that the several results stated above are de- 
duced from many trials. e same tests being tried, wi 
phosphoric in place of arsenic acid, the alkaline acetates gave 
the best results. 
The following quantitative experiments were then tried, to 
determine the relative solubility of arsenate of silver in solu- 
tions of acetates of sodium, Rochelle salt, and nitrate of am- 
monium. In experiment No. 1, 20 grms. of crystallized ace- 
tate of sodium were dissolved in a mixture of 100 ¢. c. of wa- 
, Adding more of the ammonio-nitrate to No, 3, with occa- 
‘ional drops of arsenic acid solution, to keep the mixture acid, 
& purple cloudiness appeared, which increased up to the sixty- 
p, but no precipitate fell. rE ee 
In a repetition of No. 3, (nitrate,) no precipitate fell until 
80 drops of the ammonio-nitrate of silver had been led ; 
When it reached 85 drops, the precipitate was exceedingly volu- — 
Minous. In three other experiments, the liquids were acidu- 
lated with tartaric acid. In experiment A, 75 drops of a 
hg solution of arsenic acid, 125 c. c. of water, and 25 grms, 
of crystallized acetate of sodium, were mixed, neutralized with 
Carbonate of sodium, and tartaric acid added. In B and CG, . 
gtms. of Rochelle salt and of nitrate of ammonium were 
Tespectively substituted for acetate of sodium. 
ven drops of ammonio-nitrate were then added to each of 
the solutions, In A and B, the red-brown arsenate precipi 
peared ; but in ©, no precipitate was formed except the 
toudiness due to impurities. 
Boston, Dec. 1, 1868. 
