Preparation

Carbonate of ammonia is prepared by subliming a mixture of carbonate of lime and muriate of ammonia. The muriatic acid and lime, reacting upon each other, produce chloride of calcium and water: and the water thus formed unites with the carbonic acid and ammonia to generate the compound under consideration, which rises in vapour, and is condensed in a proper recipient. During the process a portion of ammonia is liberated. The cake formed by the condensation of the vapour is broken into lumps, which should be kept in a well-stopped bottle.

Composition

This is not a neutral carbonate, as its officinal name implies, but either a sesquicarbonate, consisting of three equivalents of carbonic acid, two of ammonia, and two of water, or, as some chemists prefer to consider it, a compound of one equivalent of the proper carbonate of ammonia and one of the bicarbonate. When purified by a second sublimation, it is said to lose a portion of carbonic acid, and to become the 4-5 carbonate of ammonia, thus acquiring more stimulating properties.

Properties

The salt, as kept in the shops, is usually in whitish lumps, more or less rectangular, hard, fibrous, translucent, of a characteristic very pungent odour, and an acrid, alkaline, yet somewhat cooling taste. with a burning sensation in the throat, which renders it difficult of administration to persons of very sensitive fauces. It is very soluble in cold water, and freely dissolved by proof spirit; but is scarcely soluble in pure alcohol. By heat it is wholly volatilised. Exposed to the air, it gradually parts with the proper carbonate of ammonia, and is ultimately converted into the bicarbonate, becoming at the same time quite white, opaque, and disposed to crumble. I have noticed that, after long exposure, the resulting substance deliquesces, and ultimately assumes the liquid form.

The lumps should always be translucent when held up to the light; otherwise they have undergone more or less completely the change just referred to. which is a deterioration, as the bicarbonate is much less stimulating than the officinal salt. A loss of odour, and of the property of changing to brown the yellow colour of turmeric paper held over it, are also signs of deterioration.

Incompatibles. A solution of carbonate of ammonia is decomposed by most acids; by potassa, soda, and their carbonates; by lime-water and magnesia; alum and corrosive sublimate; by the soluble salts of lime, lead, zinc, and iron, excepting the tartrate of iron and potassa and the analogous ferruginous compounds; and by most salts with excess of acid, as the bitartrate and bisulphate of potassa.

Effects on the System

Carbonate of ammonia is irritant in its local action, and an energetic stimulant to the system. Taken internally, it occasions a sense of heat in the stomach, increases the frequency and force of the pulse, and produces a general glow through the system. Though sometimes causing a sensation of fulness in the head, it has no conspicuous influence over the special cerebral functions; and there are few substances so actively stimulant to the circulation, with so little obvious effect on the brain. It appears to excite more or less the general organic nervous system, and might even rank with the nervous stimulants: but its influence on the circulatory system is so much more decided, and its best therapeutic uses are so closely dependent on this action, that I have concluded to rank it in the present class, with this explanation as a caution to the learner. As a diffusible stimulant, it is remarkably characterized by the brevity of its action.

With its general stimulant influence on the circulation and organic nervous system, it has a tendency to increase the secretions. It often produces more or less diaphoresis, sometimes operates as a diuretie. and appears to act on the pulmonary organs, if not as an expectorant, certainly as a special stimulant of the respiratory function.

In over-doses it irritates the stomach, and, if not discharged by vomiting, which generally happens when it is given very largely, may produce dangerous inflammation of the mucous membrane, with severe burning pain. It is probably only in this way that it is capable of acting as an acute poison in the human subject; but Huxham relates a case in which its long-continued use was followed by a cachectic state of system and depraved state of the blood, as indicated by hemorrhage from the nose, gums, and intestines, pustular eruptions on the surface, dropping out of the teeth, and a general wasting of the body, with hectic symptoms. The patient ultimately died from the effects of the poison. These probably depended mainly upon a constantly sustained excess of alkalinity of the blood. Two drachms and a half given to a dog were found by Or-fila to produce gastric inflammation with tetanic spasms. The obvious antidote, should an over-dose be taken, would be one of the mild vegetable acids, as the acetic in the form of vinegar, the citric in that of lemon or lime juice, or the tartaric.