Derivation.—Native calcium carbonate, freed from most of its impurities by elutriation.

Properties.—A white, amorphous powder, often molded into conical drops; odorless and tasteless; permanent in the air. Almost insoluble in water; insoluble in alcohol.

Dose.—Horses, 1 to 2 oz.; cattle, 2 to 4 oz.; sheep and pigs, 2 to 4 dr.; dogs, 10 gr. to 1 dr.

PREPARATIONS

PULVIS CRETAE COMPOSITUS—COMPOUND CHALK POWDER

Composed of chalk, 30 parts; acacia, 20 parts; sugar, 50 parts.

Dose.—Dogs, 10 gr. to 1 dr.; cats, 1 to 5 gr.

MISTURA CRETAE—CHALK MIXTURE

Composed of compound chalk powder, 20 parts; cinnamon water, 40 parts; water to make 100.

Dose.—Dogs, 1 to 2 oz.; cats, 1 to 2 dr.

Actions.—Internally, chalk is the slowest acting antacid, because of its comparative insolubility and is of value when it can exert its long-continued influence throughout the digestive tract. It resembles bismuth in mechanically coating or protecting inflamed or irritable surfaces. It is not so astringent nor antiseptic as the bismuth salts, and these are generally preferable to chalk for the smaller animals. It is excreted unchanged in the feces. Externally it is a dessicant and slightly astringent powder, also protective.

Uses.—Chalk forms a dusting powder for moist eczema, slight burns and intertrigo; zinc oxide and starch (one to four) is, however, a better preparation. Chalk is the most useful antacid for diarrhoea accompanied by fermentation of the intestinal contents, while its local astringent and protecting influence assists in overcoming the trouble. It is especially good for foals and calves given in flour gruel and often conjoined with catechu, ginger and opium.

Chalk may be given to dogs in pills or powder; to other animals in powder, capsules or electuary. Chalk is frequently prescribed suspended in flour, gruel, milk or mucilage to the larger animals. The chalk preparations are suitable for dogs and cats.