Ammonium

AMMONIUM, NH₄, a chemical radical that cannot be obtained in a free state. Ampère (1817) and later Berzelius first pointed out that the compound of ammonia with water should be regarded as the aqueous oxide of a metal-like compound, as a "complex metal" ammonium, which, like potassium and sodium, forms salts with acid residues that dissociate in aqueous solutions into the colorless ion NH₄+; the degree of dissociation of the salts is quite significant, whereas the aqueous solution of ammonium hydroxide (NH₄OH) possesses a comparatively small electrical conductivity, because the aqueous solution dissociates primarily according to the scheme: NH₃+HOH. Among the salts of ammonium, the following can be noted as the most important: ammonium chloride—sal ammoniac, NH₄Cl (Ammonium chloratum), a colorless, dry powder with a cooling, salty taste; it volatilizes upon heating without melting, but dissociates into NH₃ and HCl, which separate by diffusion through porous partitions; it dissolves in 3 parts cold and 1.3 parts boiling water, is almost insoluble in alcohol; it is widely used in laboratories, in industry (soldering, galvanic cells, fertilizer, etc.), and also in medicine as an expectorant. In medicine, ammonium bromide and ammonium iodide are also used: Ammon. bromatum and Ammon. jodatum. Ammonium carbonate (Ammonium carbonicum) does not correspond to the formula (NH₄)₂CO₃, but represents a mixture of the acid salt NH₄HCO₃ and the ammonium salt of carbamic acid NH₂.COONH₄; white, transparent, fibrous-crystalline solid lumps, smelling strongly of ammonia (the decomposition to which the carbamic salt is more easily susceptible - NH₂.COONH₄ -> CO₂ + 2NH₃); it dissolves in approximately 4 parts of water; upon heating, it decomposes and volatilizes without residue (the use of ammonium carbonate, under the name of "ammonium," in baking instead of yeast is based on this). It is widely used in analytical chemistry, in industry—in the dyeing trade; in medicine—as a smelling salt for fainting. Among other salts, one should mention ammonium nitrate, used in medicine for producing laughing gas (see), which forms upon heating the salt: NH₄NO₃ -> N₂O + 2H₂O; in industry—it enters into the composition of many explosives (see). In a mixture with ammonium sulfate, it is widely used for fertilizer under the name of ammonium sulfate nitrate. The salt of persulfuric acid, (NH₄)₂S₂O₈ (Ammon. persulfuricum), consists of crystals soluble in 2 parts of water and decomposing in aqueous solution with the release of ozonized oxygen. It is used in medicine in the form of a 0.5–2% solution for mouth rinsing, for the preservation of food products, etc. In photography, it is used as a gentle reducer.—Regarding the pharmacological action of ammonium salts, see Ammonia.