1. The method of producing ammonium metatungstate crystals which comprises heating ammonium paratungstate at a temperature within the range of 300 F. to 700 F. until an aqueous slurry containing about 9% by Weight of the material so heated exhibits a pH of between 3 and 5; mixing the material with water at a temperature in the range from above about 70 C. to below the boiling point of water to form a slurry thereof containing from about 9% to about 10% of the material; maintaining the slurry at a temperature in the aforesaid range and adding ammonium hydroxide thereto as needed to maintain the slurry at a pH of from about 3.0 to about 5.0 until the slurry has been reduced to about one-third of its original volume; filtering the concentrated slurry; and crystallizing ammonium metatungstate from the filtrate.

 

2. The method of producing ammonium metatungstate which comprises heating ammonium paratungstate at a temperature of between about 500 F. and 600 F. to evolve ammonia and water therefrom; discontinuing said heating when an aqueous slurry containing about 9% by weight of the material so heated exhibits a pH of between about 3.5 and about 4.0; mixing the material with sufiicient Water at a temperature in the range of C. to C. to form a slurry containing from about 9% to about 10% by weight of the material; maintaining the slurry at a temperature in the aforesaid range and adding ammonium hydroxide thereto as needed to maintain the slurry at a pH of from about 3.5 to 4.0 until suificient water and ammonia has been evolved therefrom to reduce the slurry to about one-third of its original volume; filtering the concentrated slurry; and crystallizing ammonium metatungstate from the filtrate.