Prep. By neutralizing the bisulphite of soda with carbonate of soda, and crystallizing. The bisulphite is formed by saturating a solution of carbonate of soda with sulphurous acid gas.

Prop. & Comp. White prisms, having a slight odour of sulphurous acid; soluble in water. Composition (Na O, So2 + 8 HO).

Therapeutics. The same as sulphurous acid, and adapted for internal administration in cases of chronic vomiting connected with the presence of sarcinte ventriculi in the stomach. It may also be applied in the form of lotion (see Acidum sulphurosum).

Dose. 20 gr. to 60 gr.

Hyposulphite of Soda. Appendix B. [Not officinal in U. S. P.]

It occurs in large rhombic prisms with oblique faces, which are very soluble in water. The hyposulphite of soda, in common with other soluble hyposulphites has the peculiar property of dissolving chloride of silver, and also of rendering colourless a solution of iodine; the explanation of this latter phenomenon will be found among the volumetric tests. Its composition is represented by the formula, Na O, S2 O2 + 5 HO.

Use. It is introduced into the Appendix of the Pharmacopoeia for the formation of one of the volumetric solutions.

Therapeutics. The same as the Sulphite; when decomposed sulphurous acid is set free along with sulphur. Dose. 20 gr. to 60 gr.

Nitrate of Soda. Appendix A. [Not officinal in U. S. P.]

Prop. & Comp. A deliquescent salt crystallizing in obtuse rhombohedra; it is soluble in water; the solution should give no precipitate with nitrate of silver or chloride of barium, showing the absence of chlorides and sulphates. Composition (Na 0, No4).

Therapeutics. It is not employed in medicine, but is introduced for making the nitrite of soda.