Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert.
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

    243/272 (page 225)
    of arsenite and arseniate of silver precipitates. The anti- monic acid, which did not dissolve in the water, 1s dissolved in as small a quantity of nitro-hydrochloric acid as possible, and the solution evaporated as far as possible, and then tested with sulphuretted hydrogen water, when, if any antimony is present, the liquid at once assumes an orange- yellow colour; and, on boiling, decidedly orange-yellow flakes are separated. In order to detect the tin, the me- tallic precipitate is washed off the zinc in the generating bottle, and boiled with hydrochloric acid, when chloride of tin is formed, which may be detected by the well-known re- action with chloride of mercury. To effect the detection of small quantities of arsenic, in presence of a large quantity of antimony, the above process may be advantageously modified by passing the washed gases into a solution of nitrate of silver instead of into nitric acid ; the whole of the antimony is precipitated as antimonide of silver, while every trace of arsenic remains in solution in the form of arsenious acid. Onneutralizing the liberated nitric acid by ammonia, the characteristic yellow arsenite of silver is precipitated. If the gas has been passed for a long time, the solution is sometimes free from silver. In this case, the precipitate of arsenite of silver appears only after the addition of a drop of nitrate of silver. The separation of the antimony from the black precipitate, which is a mixture of metallic silver and antimonide of silver, is attended with difficulty ; to detect minute quan- tities of antimony, it is better, therefore, to follow the pro- cess first described. p. Dr. Hoffman has proposed the following method for separating cadmium from copper -—Acidify the solution, if it is notacid, with hydrochloric acid ; then pass sulphuretted hydrogen through the solution. The two metals, if present, 10 §