Abstract: A method for manufacturing alkali chromates by the reacting of chromium ore with alkali compounds and oxidation in an atmosphere containing at least 50% oxygen is described, in which the mixture consisting of chromium ore, alkali compound and optionally leaning materials is heated in a first stage in an atmosphere containing not more than 5 vol. % oxygen to a temperature between 1000.degree. and 1 400.degree. C., and in a second stage is oxidized at a lower temperature of 900.degree. to 1 070.degree. C. with supply of an atmosphere containing at least 50% oxygen.

Abstract: In the disintegration of a chromite or chromium-containing residue, wherein the chromium-containing material is disintegrated with an alkaline compound in the presence of oxygen and a diluent at a temperature above about 800.degree. C. and thereafter leached, the improvement which comprises pre-roasting the chromium-containing material prior to addition of the alkaline compound. Pre-roasting can be effected at 400.degree. to 1200.degree. C. with addition of certain amounts of silica dioxide and/or aluminum oxide and such additives, depending on the chromium containing material, if still required, are added--prior to disintegration and leaching--in such a quantity to establish a ratio of SiO.sub.2 : AL.sub.2 O.sub.3 of about 2:1 and further a ratio, calculated on the basis of NaOH as the alkaline compound, of SiO.sub.2 : Na.sub.2 O of about 1:0.5 plus a Cr.sub.2 O.sub.3 : Na.sub.2 O ratio of about 1:2 to 1:4.

Abstract: In the alkaline-oxidative disintegration of chromites into chromates with an alkali comprising reacting a chromium ore in the presence of oxygen and a diluent, and leaching the reaction mixture with at least one of water and/or a chromate-containing aqueous solution, the improvement which comprises reacting the residue obtained after leaching with an excess of alkali, based on the chromium oxide content of the residue, in the presence of oxygen, grinding the reaction mixture and, without leaching, employing the ground reaction mixture as an alkali source in another chromite disintegration cycle. The alkali reacted with the leaching residue is preferably sodium and/or potassium hydroxide and/or carbonate and is employed in about 100 to 400%, and preferably about 150 to 330%, of the stoichiometric amount based on the chromium oxide content of the leaching residue.