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.
86/526 page 62
![METANTIMONATE OF POTASSA. [§§ 50, 51, 52. § 50. 9. Bichromate of Potassa, KO,2Cr03 [K,Cr,o,]. Prepm-ation.—The commercial salt is purified by recrystallization, and 1 part of the pure salt dissolved in 10 of water for use. _ Tests.—The solution of the salt acidified with hydrochloric acid and boiled with alcohol, should yield a green solution which is not rendered turbid by chloride of barium. Uses.—Chromate of potassa decomposes most of the soluble .salts of metallic oxides by double affinity. Most of the precipitated chromates are but sparingly soluble, and many of them exhibit characteristic colours which lead readily to the detection of the particular metal which they contain. Dichromate of potassa is used principally as a test for lead, and also for separating and distinguishing bartya from strontia. § 51. 10. Acid Metantimonate of Potassa, K0,H0,Sb05 + 6aq [K,H,SbA>6H,0]. Pre2Jaration.—A mixture of equal parts of pulverized tartar-emetic and nitrate of potassa is projected into a red-hot crucible in small portions at a time. After the mass has deflagrated it is kept at a moderate red heat for a quarter of an hour longer, which causes it ta froth at first, but after some time it passes to a state of calm fusion. The crucible is now removed from the fire, and when sufficiently cold the mass is extracted with warm water; the product can now be easily washed out, and on standing deposits a heavy white powder from which the suj^er- natant liquid is decanted (Brunner). It is washed with cold water, boiled for a short time with 200 parts of water, and filtered when cold. Tests and Uses.—Acid metantimonate of potassa is very sparingl}' soluble in water, requiring 90 parts of boiling and 250 parts of cold water for solution. The solution prepared in the way described can be kept unaltered for a considerable time. It should be clear and of neutral reaction; it should give no precipitate with solution of chloride of potassium, or with solution of chloride of ammonium ; but solution of chloride of sodium should yield a crystalline precipitate with it. Metantimonate of potassa is a valuable reagent for soda, but its employ- ment requires great caution, see § 90. §52. 11. Molybdate of Ammonia, NHp,Mo03 [(NH,),MoOJ, dissolved in Nitric Acid. Preparation.—Sulphide of molybdenum is mixed with about an equal bulk of coarse quartz sand previously washed Avith hydrochloric acid, and triturated until it is reduced to a moderately fine powder; tlie powder is then heated to faint redness, with repeated stirring, until the mass has acquired a lemon-yellow colour (which after cooling tui'ns whitish). With small quantities, this operation may be conducted in a flat platinum dish, with large quantities in a muffle. The residue is extracted with sokition of ammonia, filtered, evaporated, and the pro- duct heated to faint redness until the mass appears yellow or white](https://iiif.wellcomecollection.org/image/b21966953_0086.jp2/full/800%2C/0/default.jpg)
