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:
Dec. 28, 1993
Filed:
Nov. 23, 1992
Rainer Weber, Leverkusen, DE;
Bernd Rosenow, Leverkusen, DE;
Hans-Dieter Block, Leverkusen, DE;
Norbert Lonhoff, Leverkusen, DE;
Bayer Aktiengesellschaft, Leverkusen, DE;
Abstract
A process for the preparation of sodium dichromate and sodium dichromate solutions by alkaline oxidizing roasting of chromium ores, leaching resulting roast with water, adjustment of the pH to 7 to 9.5, removal of the insoluble constituents by filtration, a sodium monochromate solution containing 300 to 400 g/l of Na.sub.2 CrO.sub.4 being obtained, conversion of the monochromate ions of this solution into dichromate ions by addition of an acid and/or by electrolysis and/or by reaction with carbon dioxide under pressure and crystallization of sodium dichromate by concentration of this solution. The improvement wherein before the conversion into a sodium dichromate solution, the sodium monochromate solution is concentrated to contents of 700 to 1000 g/l of Na.sub.2 CrO.sub.4, the monochromatic ions, the solution is subsequently freed as far as possible from sodium sulphate by cooling to a temperature of below 0.degree. C. and filtration, and the residual monochromate ions which remain in the solution are converted into dichromate ions by electrolysis and/or by reaction with carbon dioxide and/or with chromic acid.