Tungstic Acid Processing
Outline of the Process:
1. Mix 100 parts of finely ground scheelite with 60 parts of soda ash, and fuse the mixture for an hour at about 800℃.
2. Pour the molten mass into water and heat to boiling with constant stirring.
3. Allow the insoluble residue to settle and pour off the clear solution.
4. Evaporate the solution from (3) until the concentration of the sodium tungstate is about 20%.
5. Pour the hot concentrated solution into 114 lbs. of hot muriatic acid and boil for 15 minutes.
6. Allow the precipitated tungstic acid to settle pour off the acid liquor.
7. Wash with hot water containing a trace of muriatic acid, filter and dry.
8. Neutralize the acid liquor from (6) with solid caustic soda, boil and filter from any precipitate which may form.
9. Pour the filtrate into 50 lbs. muriatic acid and proceed as in (6) and (7).
10. Wash the insoluble residue from (3) with hot water. These washings are used for lixiviation in (2).
11. Decompose the residue by treating with 125 lbs. muriatic acid.
12. Allow the tungstic acid and residue to settle, pour off the liquid and wash.
13. Dissolve out the tungstic acid with 4.65 lbs. ammonia and filter from the insoluble material.
14. Pour the ammoniacal filtrate into 20 lbs. muriatic acid and proceed as in (6) and (7).