Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
98/526 page 74
![HYDROCHLORIDE OF GOLD. [§§ 73, 74, 75. § 73. 10. Palladiochloride of Sodium, NaCl,PclCl [NaPidClj. Five parts of palladium are dissolved in nitrohydrochloric acid (comp, § 72), 6 parts of pure chloride of sodium added, and the mixture ■evaporated to dryness on the water-bath. 1 part of the double salt is -dissolved in 12 parts of water for use. The brownish solution affords JXQ excellent means for detecting and separating iodine, §74. 11. Hydrochloride of Gold, HCl,AuC]3 [HAuCIJ Crystallized, HCl,AuCl3 + Caq [HAuCI^,3H,0]. Preparation.—Fine gold cuttings, either pure or an alloy with silver •or copper, are treated in a flask with nitrohydrochloric acid in excess, a gentle heat being apphed until no more of the metal dissolves: the solution is diluted with 10 parts of water. If the gold was alloyed with copper—which is known by the brownish-red precipitate produced by ferrocyanide of potassium in a portion of the solution diluted with water—the solution must be mixed with solution of ferrovis sulphate in excess; this reduces the terchloride to metallic gold, which sepai-ates in the form of a fine brownish-black jsowder. The powder thus obtained is washed with water in a small flask, and then redissolved in nitrohydrochloric acid; the solution is evaporated on the water-bath, and the crystalline residue dissolved in 30 parts of water. If the gold was alloyed with silver, the latter remains as chloride when the alloy is treated with nitrohydrochloric acid ; under these circumstances, the whole is evaporated on the water-bath with repeated addition of hydro- chloric acid, and the residue dissolved in water for use. Uses.—Chloride of gold has a great tendency to yield up its chlorine; it therefore readily converts protochlorides into higher chlo- rides, and protoxides, with the simultaneous action of water, into higher oxides. These oxidations are usually indicated by the precipitation of pure metallic gold in the form of a brownish-black powder. In the course of analysis, this reagent is used only for the detection of protoxide •of tin, in the solutions of which it produces a brownish-red or purple •<5olour or precipitate. Y. Colouring Matters and Indifferent Vegetable Substances. §75. 1. Test Papers. a. Blue Litmus Paper. Preparation.—1 part of litmus is digested with 6 parts of water, and the solution filtered ; the intensely blue filtrate is divided into 2 equal parts; the free alkali in the one half is satui-ated by repeatedly stirring the solution with a glass rod dipped in very dilute sulphuric acid, until](https://iiif.wellcomecollection.org/image/b21966953_0098.jp2/full/800%2C/0/default.jpg)
