Sodium tungstate, normal

Restriction of the molybdenum intake by young rats in a synthetic purified casein diet results in a decreased level of tissue, particularly small intestinal, xanthine oxidase. The enzyme levels arc rest tired to normal by the inclusion of sodium molybdate and other molybdate compounds. Sodium tungstate is a competitive inhibitor of molybdate, and dietary intakes of tungstate greatly reduce the molybdenum and xanthine oxidase concentrations in tissues. 

Barium Tungstates.—The anhydrous normal salt, BaW04, may be obtained by fusing together sodium tungstate, sodium chloride, and barium chloride. It crystallises in colourless octahedra—tetragonal... 

Cadmium Tungstates.—The anhydrous normal salt, CdWO, remains as colourless crystals when a mixture containing sodium tungstate (4 parts), sodium chloride (16 parts), and cadmium cliloride (11 parts) is heated to complete fusion and allowed to cool. The hydrate, CdW04.2H20, is formed by double decomposition. ... 

Calcium Tungstates.—The normal tungstate, CaWOj, occurs native as scheelite (see p. 182). It may be obtained by fusing together sodium tungstate and anhydrous calcium chloride, either with or rithout the addition of common salt/ the resulting crystals are similar in form to scheelite, that is, tetragonal bipyramidal, a c=l 1-5336,... 

Sodium Tungstates.—The anhydrous normal tungstate, NajWOi, is prepared by the fusion method described for potassium tungstate (see p. 222), or by complete dehydration of the hydrates at 100° C. or over sulphuric acid. It may be obtained from the mineral wolframite by fusion with alkali as already described (see p. 202). 

Saturation of a solution of normal sodium tungstate with carbon dioxide. ... 

Zinc Tungstates.—The anhydrous normal salt, Z11WO4, is obtained as rhombic crystals by fusing together sodium tungstate (1 part), sodium chloride (2 parts), and zinc chloride (2 parts). The monc-hjdrate, ZnW04.H20, is obtained by double decomposition as a white amorphous precipitate, slightly soluble in water. ... 

Salts of this acid ma be prepared b - boiling a mixture containing normal sodium tungstate, Na2 V04.2H26 (2 parts), s Taip phosphoric acid (3 parts), and water (1 part). The solution turns j ellow, and on... 

Tungsto-arsenates.—Only the ammonium salt, XH4)3H has been prepared. It separates as a white crystalline precipitate when a solution containing normal sodium tungstate... 

Normally, the raw sodium tungstate solution after NaOH digestion contains 200 g W04 /l, which is too high for the ion exchange process. The ion exchange capacity decreases with increasing WO3 concentration, as is shown in Fig. 5.11. 

Tungsten bronzes can be prepared by a variety of reductive techniques but probably the most general method consists of heating the normal tungstate with tungsten metal. They are extremely inert chemically, being resistant both to alkalis and to acids, even when hot and concentrated. Their colours depend in the proportion of M and W present. In the case of sodium... 

Calcium Molybdate, CaMo04, occurs Yvith the tungstate in the mineral powellite (see p. 111). The normal salt is formed as a white precipitate when calcium chloride is added to a hot concentrated solution of sodium molybdate. - It may also be obtained, in a manner similar to that used for the barium salt, as white microscopic crystals, tetragonal bipyramidal, with a c==l 1-5457. 

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