摘要:
Ammonium tungstate, ammonium paratungstate, ammonium metatungstate or hydrated tungsten trioxide is produced by passing tungstate anions through an anion exchange membrane into an aqueous solution containing ammonium cations under the driving force of an electrical potential for a time sufficient to achieve a pH within the range in which the desired tungsten compound will form.
摘要:
Heteropoly acids of tungsten and molybdenum, such as tungstosilicic acid and molybdosilicic acid, are produced by first preparing an aqueous solution of an alkali metal tungstate or molybdate and an alkali metal salt of the hetero atom, and then removing the alkali metal cations from the solution by means of a cation exchange membrane under the influence of an applied electrical potential, whereby the reactive tungstate or molybdate and hetero species anions react to form the desired heteropoly acid.