Abstract: Complex-Homogeneous Precipitation Method was developed for precipitation of tungstic acid at room temperature and low acidity.This method can also be used to remove trace molybdenum from tungsten by selective reduction decomposition when SO₂ is introduced to the mixed solution.The linear relationship between peroxotungstate and peroxomolybdate concentration in solution was established, i e. ln=[W]=kln[Mo]+A which A=ln[W]₀ - kln[Mo]₀.The separation constant k becomes large when temperature and acidic strength rise and their relationship is k rises slightly with the increase of [H⁺]²(from [H⁺]=0.5 to 4.0 mol/L) and exp (-1/T) (T=273 +t , 20≤t≤50℃).The kinetics mechanism was also discussed.

Key words: 4:2 Peroxotungstate, Selective reduction decomposition by SO₂, Removing molybdenum from tungsten