PRODUCTION OF WATER SOLUBLE TUNGSTEN COMPOUND CRYSTAL AND HIGH-PURITY TUNGSTIC ACID CRYSTAL

摘要

PURPOSE:To produce the titled crystal having less content of radioactive element and transition elements by adding high-purity inorganic acid to an aq. soln. of ammonium metatungstate. CONSTITUTION:Ammonium metatungstate is dissolved in pure water and the soln. is filtrated to obtain =50g/l concn. aq. soln. contg. tungsten. From 5-12 N conc. high-purity inorganic acid (e.g. nitric acid) is added to this aq. soln. and crystal of water soluble tungsten compd. is deposited by heating the soln. at 10-50 deg.C under stirring and filtered. A mother liquor wherein purified tungstic acid crystal is deposited therefrom is obtained by dissolving this crystal in (ultra)pure water and filtering it. After adding 3-12 N concn. high-purity inorganic acid (e.g. nitric acid) to this mother liquor and heating this soln. at =50 deg.C to deposit tungstic acid crystal, it is filtered and washed to obtain high- purity tungstic acid having =80ppb alkali metal, =1ppb radioactive element and =1ppm transition elements.