Prep. Made by evaporating solution of soda to an oily consistence, and pouring it on a clean silver or iron plate to solidify.

Prop. & Comp. It occurs in white fragments or cakes, alkaline and corrosive. Soluble in water; its solution in water acidulated by nitric acid gives scanty white precipitates with nitrate of silver and chloride of barium. Forty grains dissolved in water leave scarcely any sediment, and require for neutralization about ninety measures of the volumetric solution of oxalic acid, corresponding to 27.9 grains of soda. Composition (Na 0, HO).

Off. Prep. Liquor Sodae, above described, contains caustic soda, and in the British Pharmacopoeia is considered an officinal preparation of that substance.

Therapeutics. Soda may be employed externally as a caustic, in the same manner as potash. It is less deliquescent, and therefore more convenient, but likewise probably somewhat less powerful. It may be cast into sticks for medicinal use.