AMMONIUM

The name given to a group of atoms, which play the part of a compound basic, radical, or metallic element. This substance, whose formula is NH 4 or (NH 4 ) 2 , has never been isolated, although capable of forming most stable salts with the various acid radicals. Several attempts have been made, however, to obtain this compound radical, or group of elements, in a free state, and with more or le succe , but on account of its great instability it invariably decomposes when set free into ammonia and hydrogen. Ammonium salts are some of the most important chemical agents, and are usually recognised as follows, ammonia solution, however, usually acting in exactly the same manner as a solution of ammonium hydrate:—By imparting a deep blue tint to solutions of salts of copper. By exhalation of ammoniacal gas (recognised by its odour), when triturated or mixed and heated with caustic pota a, soda, or lime. Added to a solution of bichloride of platinum, they produce a heavy yellow, crystalline precipitate, consisting of minute octahedrons easily discernible under the microscope. With pro to nitrate of mercury, a black precipitate. With bichloride of mercury, a heavy, white precipitate. With a concentrated solution of tartaric acid, a crystalline, white precipitate, nearly similar to that given with salts of pota a. They are nearly all soluble in water, volatile, and crystallisable. Except the carbonate, they are almost invariably estimated by conversion into ammonia, and estimation by volumetric analyses, as in alkalimetry. In the laboratory, however, for exact purposes, they are converted into the double chloride of ammonium and platinum.