Aluminium silicotungstate

This compound is extremely soluble in water and three hydrates are known. The hydrate 2Al₂O₃(SiO₂.12WO₃)₃.93H₂O crystallises in regular octahedra; the hydrate with 87H₂O crystallises in rhombohedra (a:c = 1:2.6653); and the hydrate with 60H₂O forms triclinic crystals (a:b:c = 0.8563:1:1.0658; α = 87°44', β = 105°11', γ = 91°48'). The first two salts are therefore isomorphous with the corresponding gallium salts.