Sodium tungstate is an anhydrous salt of sodium tungstate formed by dissolving sodium carbonate and tungsten oxide stoichiometrically. If the anhydrous salt is recrystallized from an aqueous solution above 6°C, the dihydrate salt will be precipitated, and if the anhydrous salt is recrystallized in an aqueous solution below 6°C, the decahydrate salt will be obtained. Generally, Na2WO4 is prepared from CaWO4 etc. in industry, and its reaction formula is as follows:
CaWO4+2HCl→H2WO4+CaCl2
H2WO4+2NaOH→Na2WO4+2H2O
(1) Anhydrous salt is a white opaque orthorhombic crystal block, which is divided into three types: δ body, γ body and β body. The transformation temperature from δ to γ is about 570°C, and the transformation temperature from γ to β is about 585°C. The relative density is 4.18 (18.5°C). The melting point is 700°C. It does not change when heated to below 700°C in hydrogen, but it turns into metallic tungsten when heated to 1100°C. Solubility in water: 57.5 (0°C), 73.0 (20°C), 77.9 (40°C), 90.1 (80°C), 96.8 (100°C).
(2) Dihydrate salt is a colorless orthorhombic plate crystal with luster. The relative density is 3.23 (19°C). The melting point is 698°C. It is stable in air, and becomes anhydrous salt when heated to 100°C. The solubility in water is 82.5 g/100g (20°C). The aqueous solution is slightly alkaline (pH8~9). Form insoluble tungstic acid in water.
(3) The decahydrate salt is a colorless crystal, and it is easy to become a dihydrate salt when it is above 6°C. Rat oral LD501190 mg/kg. It is mainly used as raw material and reagent of heteropoly ammonium tungstate and other tungstates.
More details of tungstic acid product, please visit website: tungstic-acid.com
Please contact CHINATUNGSTEN for inquiry and order of tungstic acid:
Email: sales@chinatungsten.com
Tel.: 86 592 5129595
