Chemetics International Company, Ltd.

Raymond E Alford

Felix M Mok

Deceased Warren

Process for separating sulphate from a contaminating chromium component contained in an aqueous liquor by the crystallization of a sulphate compound. The sulphate may be separated substantially free of chromium component by adjustment of the pH to the range of from about 2.0 to about 6.5, followed by cooling of the liquor to precipitate the sulphate compound from solution which sulphate is subsequently removed. The process provides an effective method for the separation of sulphate from dichromate, and is particularly useful in the production of chlorate.

Process for the separation of sulphate

Metal electrodes provided with a coating consisting essentially of a mixed oxide compound of (i) a compound of the general formula ABO.sub.4, having a structure of the rutile-type, where A is an element in the trivalent state selected from the group consisting of Al, Rh and Cr, and B is an element in the pentavalent state selected from the group consisting of Sb and Ta, (ii) RuO.sub.2 and (iii) TiO.sub.2 ; wherein the mole fraction of ABO.sub.4 is between 0.01 and 0.42, the mole fraction of RuO.sub.2 is between 0.03 and 0.42, and the mole fraction of TiO.sub.2 is between 0.55 and 0.96. The electrodes have low precious metal content, provide improved durability and improved current efficiency-anodic overvoltage performance. They are used in the electrolysis of chloride containing liquors in the production of, for example, chlorine and more particularly, chlorate.

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Vancouver, Canada

Raymond E Alford