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.
84/526 page 60
![CARBONATE OF AMMONIA. 1 part of the anliydrous salt or 2-7 parts of the oystallized salt is dis- solved in 5 parts of water. :Z'es<6\—Carbonate of soda should be perfectly white. Its solution, after supersaturation with nitric acid, should not be rendered turbid b}- chloride of barium or nitrate of silver ; neither should sulphocyanate of potassium impart a red, nor warming Avith molybdate of ammonia and nitric acid a yellow, tint to it, or give a yellow precipitate; the residue which remains on evaporating its solution to dryness, after previous supersaturation with hydrochloric acid, should leave no residue (silicic acid) when redissolved in water. When fused in a glass tube with cyanide of potassium for a long time in a current of carbonic acid, it should give no trace of a dark subhmate (arsenic). See § 132, 12. Uses.—With the exception of the alkalies, carbonate of soda precipi- tates the whole of the bases in the form of neutral or basic carbonates. Those bases which are soluble in water as bicarbonates requii^e boiling for their complete precipitation from acid solutions. Many of the pre- cipitates produced by the action of carbonate of soda exhibit a charac- teristic colour, which may lead to the detection of the metals which produce them. Solution of carbonate of soda serves also to decompose many of the insoluble salts of the alkaline earths or of the metals, more particularly those containing organic acids. These salts when boiled with carbonate of soda are converted into insoluble carbonates, while the acids combine with the soda and are thus obtained in solution. Carbonate of soda is also frequently used to saturate free acids. § 47. 6. Carbonate of Ammonia, NHp,C02 [(NHJ.co,]. Preparation.—Purified sesquicarbonate of ammonia is employed, such as is prepared on a large scale from a mixture of chloride of ammo- nium and carbonate of lime by sublimation; it shovild be entirely free from any smell of animal oil. The outer and the inner surface of the mass should be carefully scraped off. One part of the salt is dissolved by digestion with 4 parts of water to which 1 part of solution of caustic ammonia has been added. Tests.—-Pure carbonate of ammonia should volatilize completely. Neither solution of nitrate of baryta nor of nitrate of silver, nor sul- phuretted hydrogen, should give any colotir or precipitate with it, after it has been supersaturated with nitric acid. Uses.—Carbonate of ammonia, like carbonate of soda, pi'ecipitates most metallic oxides and earths; it is generally employed in preference to the sodium salt, because it does not introduce a non-volatile substance into the solution. Complete precipitation of many of the oxides takes place only on boiling. Several of the precipitates redissolve again in an excess of the precipitant. In like manner, carbonate of ammonia dis- solves many hydrated oxides and sulphides, and thus enables us to distinguish and separate them from others which are insoluble in this reagent. Carbonate of ammonia, like caustic ammonia, and for the same reason, fails to prepipitate from acid solutions many oxides, which it precipitates from neutral solutions. (Compare § 53.) Carbonate of ammonia is used in analysis principally to effect the precipitation of baryta, strontia, and lime, and the separation of these substances from](https://iiif.wellcomecollection.org/image/b21966953_0084.jp2/full/800%2C/0/default.jpg)
