Process for reducing hexavalent chromium in oxidic solids, which comprises the steps: a) mixing of the oxidic solid containing Cr(VI) with a carbon-containing compound which is liquid in the range from 20 to 100° C., b) treatment of the mixture obtained after a) in an indirectly heated reactor at a temperature of from 700° C. to 1100° C., particularly preferably at a temperature of from 800° C. to 1000° C., under a protective atmosphere, c) cooling of the reaction product obtained after b) to at least 300° C., preferably at least 150° C., under a protective atmosphere.