Fine yellow tungsten oxide or fine tungsten trioxide is prepared by using double salt method. The finer the granular of yellow tungsten oxide is, the smaller the corresponding apparent density is. Fine WO3 is also produced by the reaction between artificial scheelite and hydrochloric acid (HCL).
By using double salt method to produce fine tungsten trioxide, white amorphous gel tungstic acid will be formed first if the double salt and HCL react under cold conditions. And the greater the actual bulk of gel tungstic acid with lower concentration is, the finer the particle size of prepared tungsten trioxide is. But, this is not unlimited.
Relevant process practice data show that in the case of constant acidity of reaction system, the minimum apparent density of prepared tungsten trioxide can reach 0.23~0.25g/cm3 if concentration of double salt slurry is intentionally reduced and volume of white gel tungstic acid is effectively increased. If relevant operating conditions are controlled more optimally and effectively, the apparent density of fine tungsten trioxide finally obtained in the process can be further reduced.
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