Tungstate of Soda

Sodium paratungstate is known commercially as "tungstate of soda" and may be prepared on a large scale by fusing wolframite with soda ash and lixiviating the fused mass. On nearly neutralising the boiling solution with hydrochloric acid and allowing to crystallise, large triclinic crystals of the salt separate.

The salt may be formed in solution by any of the following methods:
1.Saturation of a solution of sodium hydroxide, carbonate, or tungstate, with anhydrous tungstic acid.
2.Treatment of a sodium tungstate solution with hydrochloric acid at boiling-point (as described above) until only faintly alkaline to litmus.
3.Addition of a solution of sodium metatungstate (containing 5.8 grams Na2O.4WO3.10H2O) to one of the normal tungstate (containing 2 grams Na2O.WO3.2H2O).
4.Saturation of a solution of normal sodium tungstate with carbon dioxide.
5.Electrolysis of sodium tungstate solution in a cell in which the electrodes are separated by a diaphragm (see above).