Qualitative chemical analysis / by C. Remigius Fresenius.

Date:
1869
Catalogue details

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.

    65/320 page 53
    For the properties of the precipitate see p. 51^ 2. 3. Potash^ produces a bulky, reddish-brown precipitate of ferric hydrate (FeHgOg), which is insoluble in excess of the pre- cipitant and in salts of ammonium. 4. AmmoTiia^ produces the same precipitate, insoluble in excess of the precipitant. 5. Ferrocyanide of potassium produces, even in very dilute solutions, a fine blue precipitate of Prussian blue or ferric ferro- cyanide [Fe^(CygFe)3]. This precipitate is insoluble in hydro- chloric acid_, but is decomposed by potash, with separation of ferric hydrate. 6. Ferricyanide of potassium deepens the color of ferric solutions to reddish-brown, but it produces no precipitate. 7. Sulphocyanide of potassium^ imparts to acid solutions an intense blood-red color, arising from the formation of soluble ferric sulphocyanide. This test is the most deJicate of all; it will indicate the presence of a ferric salt when all other tests fail. The red coloration may in such cases be detected more distinctly by resting the tube upon a piece of white paper, and looking through it from the top. The sensitiveness of the reaction may be increased by adding hydrochloric acid and then ether, and shaking. The ferric sulphocyanide dissolves in the ether, and the color is concentrated. 8. Carbonate of barium (even in the cold) precipitates the iron as ferric hydrate, mixed with basic salt. Blang'ane.se. DRY REACTIONS. 1. The borax bead, when heated with compounds of man- ganese in the outer blowpipe flame, acquires when cold an amethyst-red color. The bead loses its color in the inner flame. 2. If a bead of carbonate of sodium is made in the loop of a platinum wire, touched with a finely-divided compound * Non-volatile organic acids and sugar prevent the precipitation of ferric salts by alkalies. t In ferric solutions which, have been mixed with acetate of sodium (and are more or less red from the formation of ferric acetate), no ferric sulphocyanide will be formed until a considerable quantity of hydrochloric acid has been added. The same remark applies to solutions containing an oxalate.
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