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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    solved in water and acids, and examined in the regular way. 600. Sometimes we are obliged to have recourse to the following method for destroying the organic matter, espe- cially in the case of solutions which have to be examined for poisons :—The solid substance or solution is boiled with concentrated hydrochloric acid, to which chlorate of potash, in powder, is added gradually until the mixture becomes perfectly fluid; the solution is then heated until all free chlorine is evolved, after which it is diluted with water and filtered. The filtrate must be examined in the regular way. The residue must be examined for chloride of silver. 601. THE SUBSTANCE UNDER EXAMINATION IS A PURE METAL OR AN ALLOY. 602. Nitric acid behaves with metals in the following manner :—Gold and platinum are neither dissolved nor altered in the least degree by it. Tin and antimony are converted by nitric acid into oxides, which do not dissolve in or combine with an excess of the acid. The other metals are oxidized and converted by it into soluble nitrates. On account of the different behaviour, therefore, which nitric acid exhibits with the metals, it is usual to employ it as the solvent of alloys, &e. 603. To the metal or alloy under examination, which is placed in a small flask, is added concentrated nitric acid, and heat applied. One of the three following cases will then occur :—1. Complete solution takes place. 2. A white insoluble substance separates. 8. A metallic residue re- mains. Each of the three cases are considered separately in detail. 604. 1. If complete solution ensues, GOLD, PLATINUM,* * Alloys of silver and platinum, with the latter metal le in small proportion only, dissolve in-nitric acid.