The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 16, 1993
Filed:
Aug. 27, 1991
Applicant:
Inventors:
Walter Bludssus, Vienenburg, DE;
Erk-Rudiger Feuerhahn, Osterode, DE;
Horst Zimmermann, Bad Harzburg, DE;
Assignee:
Hermann C. Starck Berlin GmbH & Co. KG, Berlin, DE;
Attorneys:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
C01G / ; C01G / ;
U.S. Cl.
CPC ...
423 65 ; 423 62 ; 423 63 ; 423 66 ; 423 67 ;
Abstract
Fluorine content of tantalum and niobium hydroxides is reduced to under 0.5 weight % by washing such hydroxide precipitates (as obtained by HF digestion and solvent extraction) with dilute ammonia (1 to 10%) and then water in two washing stages. The first washing stage includes a partial neutralization and the used wash water of the second stage is advantageously recycled, after adjustment of its ammonia concentration, for use as the first stage washing liquid.