Читать книгу Poisons, Their Effects and Detection - Alexander Wynter Blyth - Страница 52

The residue is dried and intimately mixed with three times its weight of a mixture containing 2 parts of sodic nitrate and 1 part of sodium hydrate, This is added, little by little, into a red-hot porcelain crucible. The melted mass is cooled, dissolved in a little water, a current of CO₂ passed through the solution to convert any caustic soda into carbonate, and the solution boiled. The result will be an insoluble portion consisting of carbonates of lead and baryta, and of metallic silver. The mixture is filtered; the insoluble residue on the filter is warmed for some time with dilute nitric acid; the solution of nitrates of silver, lead and barium are concentrated on the water-bath nearly to dryness so as to get rid of any excess of acid, and the nitrates dissolved in water; then the silver is precipitated by hydrochloric acid, the lead by SH₂, and the barium by sulphuric acid.