Silver Metatungstate, Ag₂W₄O₁₃

Silver Metatungstate, Ag₂W₄O₁₃.3H₂O, is prepared by mixing together boiling solutions containing equivalent quantities of sodium metatungstate and silver nitrate in the presence of a little nitric acid. On cooling, the solution deposits a crust consisting of microscopic octahedra, which readily dissolve in water and may be recrystallised (by allowing the solution to evaporate) over sulphuric acid. The salt decomposes on heating.