Chap. IV. Earths, and Earthy Salts.

379

ounces, frequently repeated ; but when long continued, itweakens the organs of digestion.

Cakbonas cai.cis prjefaratus ; olim, Creta pr;eparata, etCancrorum lapilli. Ed.

Prepared Carbonate of Lime; formerly Prepared Chalk, andCrabs Stones.

Carbonate of lime, whether the softer variety commonlycalled Chalk, or the harder variety called Crabs Eyes andCrabs Stones, after having been triturated to powder in aniron mortar, and levigated* on a porphyry stone with a littlewater, is to be put into a large vessel, and water to bepoured upon it, which, after agitating the vessel repeatedly,is to be decanted off, while loaded with minute powder.On allowing the water to settle, a subtile powder will sub-side, which is to be dried.

The coarse powder which the water could not suspend, maybe levigated again, and treated in the same manner.

Creta pryeparata. Lond.Prepared Chalk.

Take of

Chalk, one pound.

Add a little water to the chalk, and triturate it to fine pow-der. Throw this into a large vessel filled with water, thenagitate them, and after a short pause, decant off the super-natant liquid, still turbid, into another vessel, and set itaside, that the powder may subside. Lastly, having pour-ed off the water, dry this powder.

TESTJE PR^EPARATiE. Lond.

Prepared Oyster Shells.Wash the shells, previously well cleaned, in boiling water,then prepare them in the same manner as chalk is prepa-red.

Creta pr^eparata. Drib.Prepared Chalk.Grind it to powder in an earthen-ware mortar, with the ad-dition of a little water; then mix it with a sufficient quanti-ty of water by agitation j and after allowing it to stand alittle, until the coarser particles fall to the bottom, pour offthe liquor. This may be frequently repeated, trituratingpreviously each time. Finally, the very fine powder, which^