Prep. Generally prepared from gas liquor, by adding hydrochloric acid to neutralization, or by first forming a sulphate of ammonia, mixing this with common salt (chloride of sodium), and separating the hydrochlorate of ammonia (chloride of ammonium) from the sulphate of soda by sublimation, and collecting in leaden domes. It may be also made from bone spirit.
Prop. & Comp. Hemispherical cakes, or pieces of such, which have a peculiar tough, fibrous structure; crystallizes from solution in octahedra: the salt is devoid of odour, but has a strong saline taste; soluble in water, the solution being neutral [slightly reddens litmus. U. S.]; soluble also in rectified spirit: when its aqueous solution is heated with potash, soda, or lime, free ammonia is evolved; when heated with nitrate of silver it forms a copious curdy precipitate. It volatilizes with heat, and leaves no residue. The composition is represented by the formula, Nh4 Cl.
Therapeutics. Its action is not well understood; it produces no primary stimulant effect, but probably, after absorption, increases the secretions of skin and mucous membranes: by some it is considered cholagogue; by others it is regarded as emmenagogue; and there is good evidence of its action on the nervous system, as seen in its power of relieving pain in certain forms of neuralgia. It has been used as a substitute for mercury, in chronic inflammatory diseases, from an idea that it causes absorption of deposited lymph. Externally it is slightly stimulant, and supposed to have the power of dispersing tumors. It is not much used in Great Britain, but has been extensively employed in Germany and Russia in neuralgia and chronic rheumatism, and as an alterative. Externally it is applied in lotions to swollen parts, as glandular enlargements, etc.; occasionally, from the cold produced during its solution, as a refrigerant to the head.
Dose. 5 gr. to 30 gr.
Adulteration. Iron and lead are apt to be present in the commercial salt, from the apparatus employed in its manufacture; the former may arise from sublimation of chloride of iron; it stains the salt red; neither sublime by moderate heat: the former is detected upon the addition of a few drops of nitric acid and ferrocyanide of potassium, giving rise to prussian blue; the latter, 5 by a solution of iodide of potassium. Sometimes chloride of calcium is present, causing it to deliquesce.