Lead Metatungstate, PbW4O13.5H2O, is obtained as a white flocculent precipitate by double decomposition. It is insoluble in water; soluble in hot nitric acid. However, by the addition of lead nitrate to an alkali tungstate solution, a crystalline precipitate has been obtained, of composition PbW4O13.Pb(NO3)2.10H2O. This is only very slightly soluble in water, and when heated it loses 7H2O.
Lithium Metatungstate cannot be prepared by either of Scheibler's methods, i.e. by neutralising metatungstic acid with lithium carbonate, or by adding lithium sulphate to a solution of barium metatungstate. The anhydrous tetratungstate has been prepared. |