Abstract: A method is disclosed for producing crystalline ammonium metatungstate from ammonium paratungstate. The method involves heating ammonium paratungstate in a multiple hearth furnace at from about 200.degree. C. to about 400.degree. C. to form a relatively uniformly heated ammonium paratungstate. A slurry of the heated ammonium paratungstate in water is then digested at from about 70.degree. C. to about 100.degree. C. for less than about 6 hours at relatively constant volume while maintaining the pH of the slurry at from about 4.2 to about 3.0 by the addition of ammonia as necessary to form a solution of ammonium metatungstate. The resulting ammonium metatungstate solution is then evaporated to a fraction of its original volume to concentrate it and any insolubles are removed. The ammonium metatungstate is then crystallized from the concentrated solution.

Abstract: A method is disclosed for producing crystalline ammonium metatungstate from ammonium paratungstate. The method involves heating the ammonium paratungstate in a multiple hearth furnace at from about 200.degree. C. to about 400.degree. C. to form a relatively uniformly heated ammonium paratungstate, followed by digesting the heated ammonium paratungstate in water to form an aqueous ammonium metatungstate solution. The digestion is carried out by adding the heated ammonium paratungstate to the water in separate portions, the addition of each portion being followed by heating the respective resulting mixture at from about 80.degree. to about 100.degree. C. for from about 5 to about 13 hours at relatively constant volume while maintaining the pH of the respective resulting mixture at from about 3.5 to about 4.5 by the addition of ammonia as necessary.

Abstract: A process is disclosed for removing ammonia from a sodium tungstate solution. The process involves heating the solution at from about 80.degree. C. to about 95.degree. C., while at the same time maintaining the pH above about 9.4 by addition of sodium hydroxide to the sodium tungstate solution. The heating is carried out for a period of time sufficient to allow the essentially complete removal of the ammonia.

Abstract: In a two component extraction system for producing ammonium tungstate from aqueous alkali metal tungstate from aqueous alkali metal tungstate solution, the stripped organic is washed to form a wash solution which is mixed with concentrated ammonia solution to form an aqueous ammonia solution which is mixed with product ammonia tungstate and fed as the stripping solution for contacting the loaded organic extractant.