"Take of hydrochlorate of ammonia, a pound; chalk, dried, one pound and a half. Pulverize them separately; then mix, and sublime with a gradually increased heat."

Subcarbonas Ammoniae, Edin. Subcarbonate of Ammonia.

"Take of muriate of ammonia, one part; softer carbonate of lime, dried, two parts; separately pulverize and mix them, and sublime from a retort into a receiver kept cold."

Ammoniae Carbonas, Dublin. Carbonate of Ammonia.

"Take of muriate of ammonia reduced to powder, and well dried, carbonate of soda, dried, each one- part. Mix: then put them into an earthen retort, and sublime the carbonate of ammonia with a heat gradually increased, into a receiver kept cold."

Syn. Carbonate d'ammoniaque (F.), Kohlensaures ammonium (G.), Drooges Kohlenzuures Ammonium (Dutch), Sottocarbonato di ammoniaco (/.).

This salt is produced by a double decomposition of the substances employed. The calcium of the lime of the chalk, which is decomposed, attracts the chlorine of the hydrochlorate of ammonia, forming chloride of calcium, while the carbonic acid is attracted by the ammonia; and water is formed by the union of the hydrogen of the hydrochloric acid and oxygen of the lime, which is a compound of calcium and oxygen. The chloride of lime which is formed remains in the retort, while the sesquicarbonate of ammonia sublimes, and concretes into a cake on the sides of the receiver. The theory of the Dublin process, in which the carbonate of soda is ordered instead of chalk, is precisely the same, only less heat is required; but it is too expensive to be generally employed. The chalk, or the carbonate of soda, should be extremely well dried, and the ingredients very intimately mixed, that the decomposition may be as complete as possible. The retort should have a wide cylindrical neck; and the receiver have a nearly cylindrical form, to permit the concreted salt to be taken out without breaking the glass.1

1 Ammonia praeparata, P. L. 1788. Ammoniae subcarbonas, P. L. 1824.

Qualities. - Sesquicarbonate of ammonia has a penetrating, pungent odour, an acrid, penetrating taste, and a powerful alkaline reaction. It is usually in a white, semitransparent) hard mass, which breaks with a striated fracture; has the specific gravity of 0.9662; and is totally volatilized, when pure, in a moderate heat. It is soluble in less than four parts of water at 60°, and in an equal weight at 212°; but in the latter it effervesces, and is partially decomposed. It is soluble in proof spirit, but nearly insoluble in alcohol, which coagulates a strong solution of the salt to a spongy mass. Exposed to the air, it gradually effloresces and loses its pungent odour, and becomes a carbonate, owing either to the volatilization of the superabundant ammonia it contains, or to the absorption of carbonic acid from the air.

Bergman makes its constituents to be 45 parts of carbonic acid, 43 ammonia, and 12 water, - in 100 parts; but this statement has been shown to be erroneous; it is a sesquicarbonate, and the proportions are 55'93 carbonic acid, 28.81 ammonia, and 15.26 of water; or 2 eq. of ammonia = 34/0+3 of carbonic acid =66.72+ 2 of water=z 18: making its equivalent 119.02. Sir H. Davy, however, has found that the quantity of alkali varies according to the temperature that has been employed in the preparation: thus, when it is formed at a temperature of 300°, it contains rather more than 50 per cent. of ammonia; but at a temperature of 60°;, it contains only 20 per cent.

1 This salt is prepared on a large scale, by mixing four parts of purified sulphate of ammonia, and one part of chalk, in fine powder, and submitting it to sublimation in an iron pot, to which the heat is directly applied, and which is connected with a large earthen or leaden receiver. This receiver is fitted with a leaden cover secured by a water joint, and it has a pipe in the bottom which is left open to admit the liquid products evolved during the sublimation to escape. Greys Operative Chymist, p. 596. Large quantities, but very impure, are also produced in the distillation for the preparation of gas.

- Annates de Chimie, xxviii. 12.

Sesquicarbonate of ammonia is decomposed by the acids, the fixed alkalies and their carbonates, bitartrate of potassa, sulphate of magnesia, the metallic salts, except the potassio-tartrate of iron, baryta, lime, and partially by magnesia.

Medical properties and uses.-This salt is stimulant, antispasmodic, antacid, diaphoretic, and in large doses emetic. It is beneficially given in gout, hysteria, and dyspeptic affections, when much acid is present in the stomach; and in infantile convulsions connected with dentition, or with acidity of the primae vise. As a diaphoretic it is occasionally exhibited in chronic rheumatism, in combination with guaiacum; and sometimes, although rarely, it is employed to produce vomiting in gouty and paralytic cases. From the ammonia it contains in excess, the sesquicarbonate is applied as a local stimulant to the nostrils in syncope, hysteria, and languors; and with the addition of a little scent, forms the common smelling-salts of the shops. One part of pulverized sesquicarbonate of ammonia, and three parts of extract of belladonna, spread on leather in the form of a plaster, is an excellent application for allaying rheumatic pains. The ordinary dose is from grs. v. to grs. xx. formed into pills, or dissolved in any aqueous vehicle; but to excite vomiting 3ss. may be given for a dose, and repeated if necessary, assisting its operation by plentiful dilution.

Officinal preparations. - Liquor Ammoniae Sesquicarbonatis, L. Liquor Ammonia? Acetatis, L. E. D. Linimentum Ammoniae Sesqtiicarbonatis, L. Cupri AmmoniosuIphas, L. E. D. Spiritus Ammoniae, D.