H. C. Starck, Gmbh & Co Kg

Hermann C. Starck Berlin Gmbh & Co Kg

Hermann C. Starck Gmbh & Co. Kg

Herman C. Starck Berlin Gmbh & Co. Kg

Walter Bludssus

Karlheinz Reichert

Joachim Eckert

Udo Sulkowski

Erk-Rudiger Feuerhahn

Horst Zimmermann

Uwe Bohmke

The present invention relates to a process for removing antimony from hydrofluoric acid solutions which contain Ta/Nb and have an acidity of &gt;18 N, by addition of a base metal reducing agent to the solution and heating at 40 to 60.degree. C. for 4 to 8 hours.

Process for removing antimony from hydrofluoric acid solutions which

Phase-pure, crystalline tungstates of general composition Me(II)WO.sub.4, where Me(II)=Co, Ni, Zn, Pb, Mg, Ca, Sr and/or Ba. These are prepared by wet mixing tungsten components (preferably ammonium paratungstate or metatungstate) with corresponding sponding Me(II) oxides and used, preferably, in making perovskites and X-ray intensifier phosphors.

Metal tungstates and method of preparing them and their use

Improved solvent extraction recovery of tantalum and niobium oxides from an acid solution of raw materials containing such oxides wherein the charged organic solvent [e.g., MIBK] is washed out (a) with 8-16N sulfuric acid and then (b) with water or dilute HF. This avoids the use of a second mineral acid addition after digestion by HF of raw materials (and avoids problems attendant to use a second mineral acid).

Process for the recovery and separation of tantalum and niobium

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.

Process for the preparation of tantalum/niobium hydroxides and oxides

A highly pure tantalum pentoxide powder and a process for its preparation are disclosed. The powder is substantially free of impurities and is further characterized by improved flow characteristics.

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Vienenburg, Germany

Walter Bludssus