Critical study of methods employed in ion esparation of chromium (III) from other elements-iron (III) and aluminium (III)

Methods previously reported for the quantitative separation of chromium (III) from iron (III) or aluminum by ion exchange chromatographic processes have been reinvestigated. Methods based on the fast reaction rates of iron (III) or aluminum (III) with thiocyanate ions, citrate ions and oxalate ions as eluting solutions have been found to give poor results. The method based on the oxidation of chromium (III) to chromium (VI) in an acid medium has also been found to give poor results. The oxidation of chromium (III) to chromium (VI) in a basic solution gave good results. The methods based on the formation of a very stable complex of chromium (III) with the thiocyanate ion while iron (III) or aluminim (III) remain uncompleted under the conditions given gave very good results. The methods based on the fast formation of complexes of iron (III) with EDTA and pyrophosphate while chromium (III) remains virtually uncomplexed under conditions given also gave very good results.