Origin. - Obtained by burning white marble, oyster shells, or the purest varieties of natural calcium carbonate.

Description and Properties. - Hard, white or grayish-white masses, which, in contact with air, gradually attract moisture and carbon dioxide, and fall to a white powder; odorless; of a sharp, caustic taste. Soluble in about 760 parts of water, insoluble in alcohol.

Used externally.

Physiological Action and Therapeutics. - Quicklime when used undiluted is caustic, producing effects similar to those described under Potassa.

For caustic purposes it is usually mixed with potassa (potassa cum calce). When lime is given in diluted solution it acts as an astringent and antacid. (See Liquor Calcis.)

The conditions for which lime is employed as a caustic are mentioned under Potassa.