Calcis Carbonas PraeCipitatum. Precipitated Carbonate of Lime

"Take of solution of muriate of lime, five parts. Add to it as much (sub) carbonate of soda, dissolved in three times its weight of distilled water, as may be sufficient to precipitate the chalk. Wash the precipitate three times in a sufficient quantity of water; then collect it, and dry it on a chalk-stone, or on bibulous paper."

1 Kentish on Burns, passim.

A double exchange takes place in this process; the chlorine separates from the lime and unites with the sodium of the carbonate of soda, while the carbonic acid combines with the lime: the chloride of sodium thus formed remains dissolved in the water, but the carbonate of lime is precipitated in the form of a white powder. It is an expensive preparation, and the benefit to be derived from a great degree of purity in this substance is not very obvious.

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Officinal preparations. - Hydrargyrum cum Creta. D. Electua-rium aromaticum, D. Mistura Cretae, D.

Calx Chlorinata. Lond. Chlorinated Lime

" Take of hydrate of lime, a pound; chlorine, as much as may be sufficient; pass the chlorine through the lime, spread in a proper vessel, until it is saturated."

"Chlorine is readily evolved from hydrochloric acid by bin-oxide of manganese aided by heat."

This is the common bleaching powder of commerce. The opinions of chymists vary with respect to its real nature: some, as Berzelius, consider it a chlorite; others, as Balard, a hypochlorite; Turner and many others, as a chloride; and lastly, a few, namely Dalton, Thomson, and Witter, as a di-chloride of lime. The quantity of chlorine absorbed by the hydrate of lime varies according to the degree of pressure, and the quantity of water present in the hydrate.

Qualities. -When pure, chlorinated lime is white; but it is seldom sufficiently pure, and usually has a brownish tint: its odour is that of chlorine, and it impresses an acrid taste on the palate. It is only partially soluble in water; and, when it is exposed to the air,,either in the dry or the moist state, it evolves chlorine, and carbonate of lime is formed. It is decomposed by the strong acids and the alkaline carbonates. It is regarded as a compound of 1 eq. of lime = 28.5 + 1 of chlorine = 35.42, making the equiv. 63.92. (Ca. Cl.)

Medical properties and uses. - It is employed merely as a disinfecting agent. The chlorine which is evolved unites with hydrogen of the sulphuretted hydrogen always present in such cases; hydrochloric acid is formed, and sulphur precipitated. When mixed with water, the chloride of lime dissolves, and, as the lime absorbs carbonic acid from the air, the chlorine is evolved.

Calcis Phosphas PrciaePitatum. Dub. Precipitated Phosphate of Lime

"Take of burnt bones rubbed into powder, one part; diluted muriatic acid, water, of each two parts. Let them be digested together for twelve hours, and strain the solution: add to it as much solution of caustic ammonia as will throw down the phosphate of lime. Wash the precipitate with much water, and finally dry it."

We are not acquainted with the use of this preparation.