Remarks on Arsenic. 341 



If the precipitate dissolves in ammonia with a yellow color, the so- 

 lution then contained no arsenious acid, but either a carbonate or a 

 chromate of copper. 



No. 3. Lime, baryta or strontia water, added to a solution of arseni- 

 ous acid, produces a white, flocky precipitate, forming the arsenide of 

 lime, baryta or strontia, which are soluble in acids and alkalies. 



No. 4. JYitrate of silver, added to a solution of arsenious acid, 

 neutralized with potassa or ammonia, gives a pale yellow precipitate, 

 which, vi'hen exposed to the light, soon becomes grey, but this test acts 

 only on the arsenides and not on the free acids. 



The phosphoric acid and its salts are also decomposed by nitrate 

 of silver. 



No. 5. Muriate of cobalt, added to a neutralized solution of ar- 

 senious acid, shows a fine rose red precipitate. 



No. 6. Muriate of nickel, applied to a neutralized solution of ar- 

 senious acid, gives an apple-green precipitate. 



No. 7. Arsenious acid, when acidulated with some sulphuric acid 

 and brought in contact with a zinc plate, presents the arsenic in its me- 

 tallic state, at the negative pole. 



No. 8. Per-chloride of mercury, (corrosive sublimate) mixed with 

 arsenious acid, and then with some lime water, produces a white flocky 

 precipitate, and not the orange yeliow one, which we obtain from the 

 combination of corrosive sublimate with limewater, known under the 

 name of aqua phagedenica lutea. 



No. 9. Hydrosulphuret o/am^Tiorzw produces, with arsenious acid, 

 a whidsh yellow precipitate, in color, characteristically different from 

 that with sulphuretted hydrogen. 



Table II, shows the precipitates of the tests with arsenic acid, which, 

 in comparison with arsenious acid, have almost all quite a different 

 character. 



No. 1. A colorless solution of arsenic acid brought into contact with 

 lime, strontia or baryta water, produces a flocky white precipitate, 

 which is soluble in an abundance of the acid. 



No. 2. Ammoniacal sulphate of copper yields a sky blue precip- 

 itate. 



No. 3. JYitrate of silver, added to a solution of arsenic acid, neu- 

 tralized with potassa or ammonia, produces a brick yellow precipitate 

 (but if the solution contains phosphoric acid, the precipitate is white.) 



No. 4. Sulphuretted hydrogen after some time forms with arsenic 

 acid, the yellow precipitate of sulphuret of arsenic. 



Vol. XIX.— No. 2. 44 



