Sodium Tungstate Preparation

Sodium tungstate is typically prepared by reacting tungsten oxide or tungstic acid with sodium hydroxide. The reaction takes place in aqueous solution and produces sodium tungstate, water, and sometimes hydrogen gas (if excess sodium hydroxide is used).

The general equation for the reaction is:

WO3 + 2 NaOH → Na2WO4 + H2O

Alternatively, if ammonium paratungstate (APT) is available, it can be converted to sodium tungstate by reacting it with sodium hydroxide:

(NH4)10[H2W12O42]·4H2O + 12 NaOH → Na2WO4·2H2O + 10 Na2[W12O40]

After the reaction is complete, the resulting solution can be filtered to remove any insoluble impurities. The filtrate can then be concentrated by evaporation to yield solid sodium tungstate.

It is important to note that the handling of tungsten compounds should be done with care as they can be toxic and carcinogenic. Proper protective equipment should be worn when handling these materials.