Prep. From the carbonate, in the same way as the bicarbonate of potash is prepared.

Prop. & Comp. It forms an opaque white powder, or minute crystals, slightly alkaline, and not caustic; soluble in water; it dissolves with much effervescence in dilute hydrochloric acid, forming a solution which does not precipitate with bichloride of platinum, nor with sulphate of magnesia, unless heated (this last negative test distinguishes it from the proto-carbonate): when supersaturated with nitric acid, its solution scarcely precipitates with chloride of barium or nitrate of silver. It loses a portion of its carbonic acid at 212°. Eighty-four grains exposed to a red heat leave 53 of an alkaline residue (carbonate of soda), which requires for neutralization 100 measures of the volumetric solution of oxalic acid. It gives a precipitate with antimoniate of potash. Composition (Na O, Co2 + HO, Co2).

Therapeutics. Very similar to bicarbonate of potash, and almost all that has been stated of the action of that salt applies to this, except that the urate of soda is very much less soluble than the potash salt, and hence soda is less adapted for the treatment of the uric acid diathesis. Other differences probably exist, but are not well made out. Some practitioners are of opinion that the bicarbonate of soda agrees better with the stomach than the potash salt.

Dose. 10 gr. to 60 gr.

Adulteration. Carbonate and sulphate of soda in an efflorescent state, detected by the magnesia and baryta tests.

Sodae Arsenias. See Arsenical Preparations.