Method of producing crystalline ammonium metatungstate.

摘要

A method is disclosed for producing crystalline ammonium metatungstate from ammonium paratungstate. The method involves heating the ammonium paratungstate at from about 130 to about 400°C for from about 1 to about 8 hours to remove some ammonia and water, and heating a slurry of the resulting heated ammonium paratungstate in water at from about 80 to about 100°C at relatively constant volume until the pH of the slurry becomes stabilized at from about 5.8 to about 6.0. The pH of the resulting pH stabilized slurry is then adjusted to from about 4.2 to about 3.0 by introducing a porous container containing a strongly acidic cation exchange resin into the slurry, the amount of resin being essentially sufficient to accomplish the pH adjustment. Thereafter the container and resin are removed from the resulting pH adjusted slurry which is then digested at from about 80 to about 100°C for from about 2 to about 6 hours at relatively constant volume to form a solution of ammonium metatungstate. The solution is then evaporated to a fraction of its original volume to concentrate it. Any insoluble material is then separated from the solution, and ammonium metatungstate is.crystallized from the solution.