Abstract: In a catalyst preparation process wherein effluent solvent or diluent is water washed to remove impurities and subsequently recycled to the process, the formation of solids upon mixing organic and aqueous phases is prevented by the admixture in appropriate proportions of effluent portions containing, e.g., an organoaluminum compound such as ethylaluminum sesquichloride and a transition metal tetrahalide such as titanium tetrachloride, respectively, then mixing with water, followed by optional neutralization of the acidic aqueous phase with a chemical base such as NH.sub.4 OH.