- Hydrate of sodium, NaHO, 40, with some impurities.

Characters. - Hard, greyish-white pencils or fibrous pieces, deliquescent in moist air, dry and efflorescent in dry air, very alkaline and corrosive.

Reactions and Tests. - It gives the tests of sodium (p. 617), and not of potassium. Its solution in water, acidulated by nitric acid, effervesces only slightly (limit of carbonate) and gives only scanty white precipitates with nitrate of silver and chloride of barium (limit of chlorides and sulphates). Impurities. - Carbonate, chlorides, sulphates.

Preparation containing Caustic Soda. Liquor Sodae...........................18.8 grains in 1 fluid ounce.

Use. - It is used as caustic like potash, but has less affinity for water, and so does not take it from the tissues and destroy them so powerfully. At the same time it has less tendency to run over adjacent parts.