Chalk, Precip′itated

Syn. Precipitated car′bonate of lime ; Cre′ta præcipita′ta , Cal′cis carb′on as præcipita′tum , L. Prep. 1. By adding to a solution of chloride of calcium, any quantity, another of carbonate of soda (both cold), and well washing the precipitate with pure water, and drying it out of the dust. 2. (Ph. D.) Solution of chloride of calcium (Ph. D.), 5 parts; carbonate of soda, 3 parts; (di olved in) water, 4 parts. 3. (B. P.) Di olve chloride of calcium, 5 oz.; and carbonate of soda, 13 oz.; each in two pints of boiling distilled water; mix the two solutions, and allow the precipitate to subside. Collect this on a calico filter, wash it with boiling distilled water, until the washing cease to give a precipitate with nitrate of silver, and try the product at the temperature of 212° F. Uses, . It is chiefly employed for making aromatic confection, cretaceous powder, and chalk mixture. That of the shops is seldom pure, the refuse of the soda-water makers (sulphate of lime) being commonly sold for it. When pure it is wholly soluble, with effervescence, in dilute hydrochloric acid. (See below .)