Colloidal particles of chromia have been prepared by forced hydrolysis of an aqueous solution containing chromium chloride hexahydrate. At elevated temperature, a controlled addition of potassium hydroxide yielded colloidal chromia particles. After the sol coagulation, amorphous dried residues (I) were converted to crystalline form (II) by heating at 1073 K. The thermal treatment was also accompanied by a reduction in both surface area (from 75 to 9 m(2)/g) and point of zero charge (pH(pzc); from 4.7 to 4.0). Chromia dissolution over the studied pH range (pH = 2-12) exhibits a parabolic trend, with minimum solubility at pH(pzc). (C) 2003 Elsevier Ltd. All rights reserved.