A system of instruction in qualitative chemical analysis / by Dr. C. Remigius Fresenius .. ; edited by J. Lloyd Bullock, F.C.S.
- Carl Remigius Fresenius
- Date:
- 1855
Licence: Public Domain Mark
Credit: A system of instruction in qualitative chemical analysis / by Dr. C. Remigius Fresenius .. ; edited by J. Lloyd Bullock, F.C.S. Source: Wellcome Collection.
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![§80.] sample are dug out with a knife, triturated in a small mortar, and the charcoal is washed off from the metallic particles, which then become visible, either in form of powder or as small flat spangles, according to the nature of the particular metal or metals present. In many cases, e. g. in the reduction of binoxide of tin, some borax may be advantageously added to the carbonate of soda, in order to render the mass more readily fusible. Carbonate of soda serves, in the second place, as a solvent. Platinum wire is the most convenient support for testing the solubility of substances in fusing carbonate of soda. The sample to be examined is made into a paste with some carbonate of soda and water, and this paste is placed upon the loop of a platinum wire and heated. A few only of the bases dissolve in fusing carbonate of soda, but acids dissolve with facility. Silicic acid differs from all other acids, inasmuch as the glass which it forms with carbonate of soda remains clear upon cooling, provided the two constituents be present in the proper proportions. Car- bonate of soda is moreover applied as a decomposing agent and flux, and more particularly to effect the decomposition of the insoluble sulphates, Iwith which it exchanges acids, whilst, at the same time, the newly formed sulphate of soda is reduced to sulphide of sodium; and of sulphide of arsenic, with which it forms a double sulphide of arsenic and sodium, and arsenite or arseniate of soda, thus converting it to a state which permits its subsequent reduction by hydrogen. Finally, carbonate of soda is the most sensitive reagent in the dry way for the detection of manganese, since when fused in the outer flame of the blowpipe, with a substance containing manganese, it produces a green opaque bead, owing to the formation of manganate of soda. § 80. 3. Cyanide of potassium (K Cy). Preparation.—See § 41. Uses.—Cyanide of potassium is an exceedingly powerful reducing agent in the dry way ; indeed it excels in its action almost all other reagents of the same class, and separates the metals not only from most oxygen com- pounds, but also from sulphur compounds; this reduction is attended, in the first case, with formation of cyanate of potassa, by the absorption of oxygen, and, in the latter case, with the formation of sulpliocyanide of potassium. By means of this reagent we may effect the reduction of metals from their compounds with the greatest possible facility ; thus we may, for instance, produce metallic antimony from antimonious acid or from sulphide of antimony, metallic iron from sesquioxide of iron, &c. The readiness with which cyanide of potassium enters into fusion facilitates the reduction of the metals greatly ; the process may usually be conducted even in a porcelain crucible over a spirit-lamp. Cyanide of potassium is](https://iiif.wellcomecollection.org/image/b28080361_0085.jp2/full/800%2C/0/default.jpg)
