Читать книгу Poisons, Their Effects and Detection - Alexander Wynter Blyth - Страница 49

The ammonium sulphide solution is evaporated to dryness in a porcelain dish, strong nitric acid added and again dried. To this residue a little strong caustic soda solution is added, and then it is intimately mixed with three times its weight of a mixture composed of 2 of potassic nitrate to 1 of dry sodium hydrate. This is now cast, bit by bit, into a red-hot porcelain crucible. The whole is heated until it has melted into a colourless fluid.

Presuming the original mass contained arsenic, antimony, and tin, the melt contains sodic arseniate, sodic pyro-antimonate, sodic stannate, and tin oxide; it may also contain a trace of copper oxide.

The melt is cooled, dissolved in a little water, and sodium bicarbonate added so as to change any caustic soda remaining into carbonate, and to decompose the small amount of sodic stannate; the liquid is then filtered.

The filtrate will contain the arsenic as sodic arseniate; while on the filter there will be pyro-antimonate of soda, tin oxide, and, possibly, a little copper oxide.

The recognition of these substances now is not difficult (see the separate articles on Antimony, Tin, Zinc, Arsenic, Copper).