Coarse yellow tungsten oxide or coarse tungsten trioxide may be prepared by the ammonium paratungstate - sodium complex salt method. And the coarser the particle size of prepared tungsten trioxide is, the greater the corresponding apparent density is.
The Laws of Coarse Tungsten Trioxide Produced by Complex Salt Method
1. The apparent density is greater if the particle size of tungsten trioxide prepared by maintaining the original grain structure of "ammonium paratungstate - sodium complex salt" is coarser. This is because the double salt itself has very coarse grains.
2. Acidolysis between the complex salt and HCL, if the concentration of complex salt water slurry and the reaction temperature are higher, the particle size of the prepared tungsten trioxide is also coarser and vice versa.
3. For the intermediate products such as tungstic acid and ammonium paratungstate in this process, the higher the calcination temperature is, the coarser the particle size of tungsten trioxide is.
Coarse tungsten trioxide may also be prepared by the reaction between concentrated nitric acid (HNO3) and artificial scheelite at high temperature.
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