(Sodium Orthophosphate.)

Origin. - Prepared by digesting bone ash with sulphuric acid. The solution is filtered, and to it is added sodium carbonate, and the filtrate evaporated to crystallization.

Description and Properties. - Large, colorless, monoclinic prisms, odorless, and having a cooling, saline taste. The crystals effloresce in the air, and gradually lose 5 molecules of water of crystallization. Soluble in 5.5 parts of water; insoluble in alcohol. Sodium phosphate should be kept in well-stoppered bottles, in a cool place.

Dose. - 5 grains to I ounce (0.32-32.0 Gm.) [30 grains (2 Gm.), U. S. P.].

Official Preparations

Sodii Phosphas Exsiccatus, 15 grains (1 Gm.).

Sodii Pyrophosphas, 30 grains (2 Gm.).

Sodii Phosphas Effervescens, 2 drams (8 Gm.).

Liquor Sodii Phosphatis Compositus, 2 drams (8 Cc), are all useful.