Present name. - Hydro-disodic Arseniate. Na2Ha8o4, 12H10.

Arseniate of Soda.

May be prepared by adding Carbonate of Soda to a hot solution of Arsenic Acid, and allowing it to crystallize on evaporation.

Characters and Tests. - In colourless transparent prisms soluble in water; the solution is alkaline, giving white precipitates with Chloride of Barium, Chloride of Calcium, and Sulphate of Zinc, and a brick-red precipitate with Nitrate of Silver, all of which are soluble in Nitric Acid. Heated to 300°, it loses 40.38 per cent. of its weight. A watery solution of 10 grains of the residue, treated with 53 grain measures of the volumetric solution of Soda, continues to give a precipitate with the volumetric solution of Nitrate of Silver until 1,613 grain measures of the latter have been added.

No proving of this has been made, but it has been found useful in certain forms of scrofula.

Preparation. - Solution in water up to 1, using distilled water to which 5 per cent. of rectified spirit has been added for 3x and 2, dilute alcohol for 3, and afterwards rectified spirit.