Process for the production of sodium dichromate

US5250274A · kind A · utility

Assignee

• BAYER HEALTHCARE LLC · DE

Inventors

• Norbert Lonhoff · Leverkusen, DE
• Bernhard Spreckelmeyer · Johannesburg, ZA
• Hans-Dieter Block · Cologne, DE
• Rainer Weber · Leverkusen, DE
• Jost Halstenberg
• Bernd Rosenow · Leverkusen, DE

Key dates

• Filing date: Jan 21, 1992
• Grant date: Oct 5, 1993
• Expiry date: Jan 21, 2012

Classification

• Technology area (CPC C): Chemistry; Metallurgy
• CPC primary: C01G37/14
• WIPO field: Materials, metallurgy
• WIPO sector: Chemistry

Abstract

The invention relates to a process for the production of sodium dichromate and sodium dichromate solutions by oxidative roasting of chrome ores under alkaline conditions, leaching of the furnace clinker obtained with water or an aqueous chromate-containing solution, adjustment of the pH to from 7 to 9.5, removal of the insoluble constituents by filtration, a sodium monochromate solution being obtained, conversion of the monochromate ions of this solution into dichromate ions by acidification and crystallization of sodium dichromate by concentration of this solution, characterized in that the acidification is carried out with carbon dioxide under pressure with removal of sodium hydrogen carbonate, the remaining solution is then very largely freed from sodium monochromate by cooling to a temperature below 10.degree. C. and filtration, any monochromate ions still present in the remaining solution are converted into dichromate ions by addition of an acid and the sodium monochromate filtered off is added to the sodium monochromate solution before conversion with carbon dioxide into a sodium dichromate solution.