Process for the preparation of sodium dichromate

Details Process for the preparation of sodium dichromate Process for the preparation of sodium dichromate

1992-11-23

1993-12-28

Straub, Gary P.

Chemistry of inorganic compounds

Oxygen or compound thereof

Metal containing

423 58, 423 61, C01G 3714

Patent

active

052737357

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.

REFERENCES:
patent: 3027245 (1962-03-01), Kearley
patent: 3137541 (1964-06-01), Cooke
patent: 3305463 (1967-02-01), Carlin
patent: 3933972 (1976-01-01), Bauwens et al.
Winnacker-Kuchler, Chemische Technologie (Chemical Technology), vol. 2, 4th edition, 1982, p. 657 to p. 664.

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