There are a considerable number of stable crystalline salts of the ammonium ion,
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. Several are of commercial importance because of large‐scale consumption in fertilizer and industrial markets. These salts are often isomorphous and have similar solubility in water. Compounds in which the ammonium ion is combined with a large, uninegative anion are usually the most stable. Ammonium salts containing a small, highly charged anion generally dissociate easily into ammonia and the free acid. Both normal or neutral ammonium acetate, NH
4
C
2
H
3
O
2
, and the acid salt are known. Ammonium bicarbonate is easily formed. It is produced as both food and standard grade. Normal ammonium carbonate, a crystalline solid, is the principal ingredient of smelling salts because of its characteristic strong ammonia odor. Diammonium citrate is made by neutralization of citric acid. The crystalline or granular product is used as a chemical reagent and as a diuretic. Ammonium chloride, ammonium bromide, and ammonium iodide are crystalline, ionic compounds that exhibit high vapor pressures at elevated temperatures and sublime readily. Aqueous solutions of ammonium halides are acidic. A process based on metathesis or double decomposition is generally preferred for manufacture of ammonium chloride. Several commercial grades are available. Ammonium chloride is used as a nitrogen source for fertilization of rice, wheat, and other crops. Ammonium chloride serves as an electrolyte in the manufacture of drycell batteries, is also used to make quarrying explosives. Ammonium bromide and iodide are manufactured either by the reaction of ammonia with the corresponding hydrohalic acid or by the reaction of ammonia with elemental bromine or iodine. Ammonium bromide is used to manufacture chemical intermediates, and in photographic chemicals. There are two fluoride salts of ammonia: ammonium fluoride, principally a laboratory reagent, and ammonium bifluoride, used primarily as a less hazardous substitute for hydrofluoric acid. In addition to frosting glass, uses of the bifluoride include removing scale from boiler tubes and defouling oil wells. Properties, manufacture, and applications are described. Ammonium nitrate, a white, crystalline salt that is highly soluble in water, is the most commercially important ammonium compound both in terms of production volume and usage. It is the principal component of most industrial explosives and nonmilitary blasting compositions; however, it is used primarily as a nitrogen fertilizer. Ammonium nitrate is considered a very stable salt, but when heated to temperatures from 200 to 230°C, exothermic decomposition occurs. The reaction is rapid, but can be controlled. Above 230°C, exothermic elimination of N
2
and NO
2
begin, and a final violent exothermic reaction occurs with great rapidity when ammonium nitrate detonates. When used in blasting, ammonium nitrate is mixed with fuel oil and sometimes sensitizers such as powdered aluminum. Modern commercial processes for ammonium nitrate rely almost exclusively on the neutralization of nitric acid with ammonia. Ammonium nitrate can be considered a safety material if treated and handled properly. Potential hazards include those associated with fire, decomposition accompanied by generation of toxic fumes, and explosion. Many plants outside of North America prill or granulate a mixture of ammonium nitrate and calcium carbonate. Production of this mixture, often called calcium ammonium nitrate, essentially removes any explosion hazard. Ammonium sulfate, a white, soluble, crystalline salt, is produced from the direct neutralization of sulfuric acid with ammonia. Used as a fertilizer, it is valued both for its nitrogen content and for its readily available sulfur content. Ammonium sulfide and ammonium hydrosulfide are used by the textile industry.
Most quaternary ammonium compounds produced in the United States are formulated into consumer products. The largest markets for quaternaries are fabric softening, hair care, bactericidal and germicidal applications, and for manufacture of organoclays. When one of the alkyl groups contains ∼ 10 carbon atoms, the molecules exhibit surface‐active properties. Physical properties are determined by the chemical structure of the material. Reactions include eliminations, displacements, and rearrangements. There are also many biologically important quaternaries. Most quaternaries are biodegradable. Quaternaries are prepared by the reaction of a tertiary amine with an alkylating agent. Commercial production from natural fats and oils, α‐olefins, and fatty alcohols is described. Quaternized esteramines are gaining market share in Western Europe. Other classes of quaternaries include phase‐transfer catalysts, polyamine‐based quaternaries, and perfluorinated quaternaries.
