Prep. By precipitating a solution of chloride of calcium with carbonate of soda, collecting and drying at 212°.

Prop. & Comp. Ca O, Co2. A white crystalline powder, in other respects corresponding with creta praeparata.

Creta Praeparata. Prepared Chalk. Chalk reduced to a very fine powder and elutriated.

Prop. & Comp. In white powder, or small friable masses, tasteless, insoluble in water; entirely soluble with effervescence, in dilute hydrochloric acid; the solution is not precipitated by sulphuretted hydrogen, nor, after boiling, by ammonia added in excess; saccharated solution of lime added to a neutral solution gives no or scarcely a trace of precipitate, indicating the absence of silica, common metallic impurities, alumina, or magnesia. Composition (Ca O, Co2).

Off. Prep. Mistura Cretae:. Chalk Mixture. (Prepared chalk, a quarter of an ounce; gum arabic, in powder, a quarter of an ounce; syrup, half a fluid ounce; cinnamon water, seven fluid ounces and a half.) [Prepared chalk, half a troy ounce; sugar, gum arabic, each, 120 grains; cinnamon water, water, each, four fluid ounces. U. S.]