Sal ammoniac is procured from several sources, but is at present prepared chiefly, on a large scale, from the impure ammonia obtained in the manufacture of coal gas, and in the destructive distillation of bones.

Sensible and Chemical Properties. It is either in white, translucent, concavo-convex cakes, or fragments of such cakes, of a tough fibrous structure, inodorous, of a saline and pungent or acrid taste, very soluble in water cold or hot, producing cold while dissolving, and soluble also in alcohol, though but slightly so when that liquid is concentrated. The salt deliquesces somewhat in a moist air. It is chemically characterized by being completely volatilized by heat, by yielding the odour of ammonia when rubbed with lime, and by affording, on the addition of nitrate of silver to its solution, a white precipitate of chloride of silver, which darkens on exposure, and is insoluble in nitric acid cold or hot, but is readily dissolved by solution of ammonia. It renders corrosive sublimate more soluble in water, and, by reaction with calomel, produces a solution which may act violently as a corrosive poison.

Incompatibles. These are the alkalies and alkaline earths, the strong acids, and the soluble salts of lead and of silver.

Effects on the System

Muriate of ammonia is a local irritant, and, when absorbed, acts as an alterative, increasing secretion, and probably stimulating generally the cell-action, while it exercises little if any influence on the heart.

In its local effects, it moderately irritates, and, very freely applied, may inflame the skin, though much less energetic in these respects than the carbonate. Internally taken, if swallowed in powder, it produces a vol. ii.-25 feeling of coolness in the stomach, but, in solution, causes the contrary-sensation of warmth, which, if the dose is somewhat large, may be attended with epigastric uneasiness or oppression. The secretions are notably increased, especially that of the bronchial tubes, and other mucous membranes. Diuresis and perspiration are also frequently induced, and menstruation is said to be promoted. Very freely taken, the salt is apt to operate on the bowels; but, in small doses, is said rather to favour constipation than otherwise. The pulse is either diminished in frequency, or not affected.*

With these effects there is an alterative influence, exhibited in the resolution of tumefactions, and the softening of indurations, which may be attributed to a stimulant influence on the ultimate cell-action, resembling that of mercury and iodine.

In over-doses, sal ammoniac is said to occasion vomiting and purging, with other symptoms of gastro-enteric inflammation. On the inferior animals it has been found, when very largely given, to produce poisonous effects, consisting in inflammation of the alimentary canal, and great disturbance of the nervous system, as indicated by convulsions, paralysis, and coma. it has been asserted, moreover, to cause inflammation of the stomach in these animals, when introduced largely into the circulation through any other avenue.

I have met with no account of fatal effects from it in man; but it might, no doubt, prove poisonous in a very large quantity, taken at one dose. Sundelin states that its long-continued use disorders digestion, but does not produce general cachexia. He had given it for months, in large doses, and seen no other ill effects than those exhibited by the digestive organs. (Sundelin, quoted by Pereira, Mat. Med., 3d ed., p. 448.) The salt is asserted, when freely taken, to have entered the circulation, and to have escaped by the emunctories unchanged.

From what has been stated, the inference will be drawn that muriate of ammonia, when it may seem to be indicated, may be given pretty freely without apprehension of serious consequences; the simple rule being observed, to restrain it within the point of producing gastro-enteric irritation.

Therapeutic Application

It is uncertain when sal ammoniac first came into use as a medicine. it was probably known to the ancient Egyptians; but we have no positive evidence of the fact. its authentic history ascends only to the period of the Arabians. Though until recently comparatively little employed in this country or in Great Britain, it was much used on the continent of Europe, especially by the German physicians; and is now beginning to be highly esteemed with us. The main purposes which it is thought to answer are, to stimulate the secretions, and, through its alterative properties, to promote the resolution of tumefactions and indurations, and obviate chronic inflammation.

* The following are results of experiments, made by Dr. Alexander Lindsay, of Scotland, on healthy individuals, who took daily, for a week, in divided doses, quantities varying from 9 to 18 grains. The appetite was increased, the quantity of food taken was at least doubled, and the alvine and urinary evacuations were augmented, the daily excess of solids discharged with the urine being from 70 to 160 grains. On the second day, a remarkable buoyancy of the system was experienced. The pulse was in two of the individuals diminished in force and frequency, in a third was accelerated. (Am. Journ. of Med. Sci., Jan. 1856, from Glasgow Med. Journ.) - Note to the second edition.

It is given in all febrile diseases, after the subsidence or reduction of excitement, in which the secretions are scanty, and the depuration of the blood imperfect; and especially when there is an indication for an increase of the mucous secretions, or for an alterative influence on diseased mucous membranes.

In inflammations, too, it is looked on as a most valuable resource, being given in the advanced stages, under the same circumstances precisely as those which, with us, are usually considered as indicating the use of mercurials. it is believed to act favourably by promoting the secretions, modifying the disposition to fibrinous exudation, and hastening the absorption of the fibrin already exuded. Acute inflammations of the air-passages, of the gastric mucous membrane, and of the urinary passages, pleuritis, peritonitis, and pneumonia are among the complaints in which it has been specially recommended. in pneumonia it is believed to promote the resolution of the hepatized lung. in pseudomembranous croup, and bronchitis of the same character, it is thought to favour the loosening and expulsion of the false membrane, as well as to modify the tendency to its formation. But, in all these inflammations, it should be preceded by the necessary depletory measures.