Analysis.—Scheele‘s green is insoluble in water, but is soluble in ammonia, the solution having a blue colour, from the separation of the arsenious acid from the oxide of copper. If a few drops of the blue ammoniacal solution be poured on some crystals of nitrate of silver, the yellow arsenite of silver is formed. The blue ammoniacal solution, if acidified with HCl and boiled with pure copper foil, deposits arsenic on the copper, which, if cut into strips and placed in a small reduction tube and heated, sublimes and is deposited in octahedral crystals on the cold portion of the tube. The tests before described are applicable for the detection of this substance.
Orpiment
Orpiment, or yellow arsenic, one of the sulphurets of arsenic, has been used occasionally as a poison. It is also largely employed in the arts for paper-staining and for colouring toys. In cases of arsenical poisoning, it is this compound that is commonly found adhering to the stomach and intestines. It is formed by the sulphuretted hydrogen, the result of decomposition, acting on the white arsenic swallowed.
Realgar
Realgar, or red arsenic, is another of the sulphurets of arsenic, and, like orpiment, is largely used in the arts as a colour. It is also employed, like orpiment, as a depilatory, fatal results having followed its use for this purpose. The colour of this substance prohibits its frequent use as a poison.
Both of these compounds owe their poisonous properties to the amount of free arsenious acid which they contain, and which may be as much as 30 per cent.
Symptoms.—The symptoms produced by these substances are similar to those caused by arsenic. The fatal dose will depend on the amount of free arsenious acid which they may each contain.
Treatment.—Emetics and demulcent drinks.
Metallic Arsenic, &c.
Metallic arsenic, fly powder, arsenic acid, largely used in the manufacture of magenta, aniline red, or fuchsine, and the arseniates of potash and soda, are all poisonous. The papier moure of the shops consists of blotting-paper steeped in a solution of arseniate of potash. Macquer‘s neutral arsenical salt is the binarsenate of potash.