Formation of Cr(III) hydroxides from chrome alum solutions .1. Precipitation of active chromium hydroxide

The formation of active chromium hydroxide, Cr(OH)(3) . 3H(2)O, was studied through potentiometric titrations and turbidimetric measurements. UV-Vis and IR spectroscopies were also employed to characterize the synthesized solid, The rapid addition of NaOH solution to aqueous chrome alum (KCr(SO4)(2) . 12H(2)O) solutions caused the immediate precipitation of the active material. Only monomeric Cr(III) species seemed to be participating in the precipitation process; neither chromium polymers nor complexes with anions (SO42-, Cl-, NO3-, ClO4-) influenced the fast formation of Cr(OH)(3) . 3H(2)O. Titration studies allowed the determination of several hydrolysis and precipitation constants for Cr(III). Nevertheless, they cannot be used for the estimate of Cr(OH)(3)(0) formation constant. (C) 1996 Academic Press, Inc.