Spectrophotometric investigation of titanium and zirconium complexing with xylenol orange

Interaction of titanium (4) and zirconium with xylenol orange (H6R), purified by gel-filtration is investigated. Zirconium at the optimum for photometric determination pH values 1.5-1.8 independent of the M:H6R ratio forms a complex of the composition 1:1 with λmax=555 nm. In more acid medium (pH ∼ 0.7) in case of metal excess complex of the composition Zr:H6R=2:1 with λmax=551 nm is formed. With reagent concentration increase the complex transforms into the complex of the composition 1:1. Both metals interact in the form of M(OH)22+, replacing two protons from each reagent ion of H4R2- (zirconium) and H3R3- (titanium)