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880 Preparations and Compositions. Part III.

after some time, will subside in the decanted liquor, is to becollected and dried upon a bibulous stone or paper.

Ostrearum test.5: pRiEPARAT.5^ Prepared Oyster Shells,Ovo rum test M pr^,parat^, Prepared Egg Shells,

Are to be prepared in the same manner as chalk.

The preparation of these substances merely consists in re-ducing them to an impalpable powder.

Medical use. —Carbonate of lime is commonly called anabsorbent earth. It certainly is an antacid ; that is, it com-bines with and neutralizes most acids, while its carbonic acidis expelled in the form of gas. It is therefore exhibited in af-fections of the stomach accompanied with acidity, especiallywhen at the same time there is a tendency to diarrhoea. Thefear of its forming concretions in the bowels, is probably ima-ginary ; for it is not warranted either by theory or expe-rience.

Applied externally, carbonate of lime may be considered asan absorbent in another point of view; for its beneficial ac-tion on burns and ulcers probably arises entirely from its im-bibing the moisture or ichorous matter, as a sponge woulddo, and thus preventing it from acting on the abraded sur-faces, and excoriating the neighbouring parts.

CRETA PRiECIPITATA. Dub.

Precipitated Chalk.

Take of

Water of muriate of lime, any quantity.

Add as much carbonate of soda, dissolved in four times itsweight of distilled warm water, as is sufficient to precipitatethe chalk. Wash the matter which falls to the bottom,three times, by pouring on, each time, a sufficient quantityof water. Lastly, having collected it, dry it upon a chalkstone or paper.

This preparation affords carbonate of lime in its pureststate, and, although expensive, may be employed when it isintended for internal use.

Calcis murias. Lond.Muriate of Lime.Take of

The salt which remains after the distillation of the subcar-

bonate of ammonia, two pounds ;Water, one pint.