Sodium ditungstate

Barium ditungstate, BaO.2WO3.HoO, is obtained according to Lefort by double decomposition from solutions of sodium ditungstate and barium acetate, as a white amorphous precipitate, slightly soluble in water. The existence of this compound has been disputed. ... 

Calcium ditungsiiaic in the anhydrous state was supposed by Lefort to result from the double decomposition of sodium ditungstate and calcium acetate, whilst concentration of the mother-liquor yielded crystals prc-sumed to be the trihydrate. However, the existence of these compounds is not established since the products obtained vary in composition. 

Ferrous ditungstate, PeO.2WO3.2H2O, results as a dlmamon-bro vn precipitate when a ferrous salt is added to a solution of sodium ditungstate. 

Strontium ditungstate. SrO.SWOj.sHjO, is described by Lefort as a white precipitate formed by the addition of strontium acetate to sodium ditungstate solution. It is only slightly soluble in water and becomes anhydrous on heating. 

The ditungstate, ZnO.2WO3.8H2O, is obtained as needle-shaped crystals on adding a zinc salt to a solution of sodium ditungstate and concentrating the mixture. It is soluble in 10 parts of water at 15 C. 

See also Isolation of samarium, europium, and ytterbium materials by means of sodium amalgam, synthesis 10 Sodium monothiophos-phate, synthesis 28 Tripotassium enneachlo-ro ditungstate (III), synthesis 38... 

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