Na2WO4 tungsten dioxide and sodium carbonate are melted according to the calculated amount to obtain anhydrous sodium tungstate. The anhydrous product is recrystallized in an aqueous solution above 6°C to obtain dihydrate crystals. Below this temperature, the decahydrate is obtained.
In industry, wolframite [(Fe, Mn) WO4] or scheelite [Scheelite][CaWO4] and artificially synthesized scheelite are extracted with sodium hydroxide solution to obtain crude sodium tungstate, which is converted with acid Become H2WO4, and then use sodium hydroxide to make Na2WO4•2H2O:
CaWO4+2HCl→H2WO4+CaCl2
H2WO4+2NaOH→ Na2WO4+2H2O
The anhydrous substance is a white opaque crystal block with three crystal forms of δ, γ, and β. The transition temperature from δ to γ is about 570°C, and the transition temperature from γ to β is about 585°C. The relative density is 4.18 (18.5°C), and the melting point is 700°C. Even if it is heated to 700°C in hydrogen, it will not change, and it will turn into metal tungsten at 1100°C. When heated together with chlorine gas, it turns into yellow oxychloride.
The dihydrate Na2WO4•2H2O is a very thin colorless orthorhombic plate crystal with luster. The relative density is 3.23 (19°C), and the melting point is 698°C. It is stable in air and becomes anhydrous when heated to 100°C. The solubility to water is 82.5g/100g (20°C), and the aqueous solution is slightly alkaline (pH= 8-9). It decomposes under the action of acid and crystallizes tungstic acid which is insoluble in water.
Decahydrate is a colorless crystal. It is easy to transform into dihydrate above 6°C.
More details of tungstate product, please visit website: tungstate.net
Please contact CHINATUNGSTEN for inquiry and order of tungstate:
Email: sales@chinatungsten.com
Tel.: 86 592 5129595
