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.

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    volumes of which dissolve one volume of the gas; this solution reddens litmus paper. On exposing the gas in a state of solution to the air, it is decomposed, water being formed, and sulphur in a highly divided state being sepa- rated. 401. Most metallic sulphides dissolve with decomposition in hydrochloric acid, in which case SULPHURETTED HYDRO- GEN 1s evolved, which from its characteristic smell is easily recognised. When the quantity is so minute that the smell fails to afford a sufficient proof, it may be detected by holding a piece of paper moistened with a solution of any soluble sar OF LEAD over the mouth of the test-tube, as a brown or black coating of suLPHIDE OF LEAD will be formed upon the paper. 402. When sulphides are dissolved in nitric or nitro- hydrochloric acid, SULPHURIC ActD is formed along with a separation of sulphur, which may be recognised by its colour, and also its behaviour upon ignition. In the case of sulphides, therefore, which, from their insolubility in hydrochloric acid, must be dissolved in nitric or nitro- hydrochloric acids, the sulphur is converted into sulphuric acid, and not given off as sulphuretted hydrogen. 403. 'To ascertain whether the sulphur existed in an un- oxidized state, when nitric or nitro-hydrochlorie acid has been employed as the solvent of the substance under exami- nation, a small portion of the original substance, in fine powder, must be fused with a little solid hydrate of potash or soda, ina platinum spoon, by means of the blowpipe flame. The fused mass must then be dissolved in a little water and filtered; a bright strip of silver (or polished coin) is put into the solution, and the fluid warmed. If a sulphide were present, a brownish-black film of sulphide of silver would form upon the metal. This film may be