[en] 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 λ_max=555 nm. In more acid medium (pH ∼ 0.7) in case of metal excess complex of the composition Zr:H₆R=2:1 with λ_max=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 H₄R^2- (zirconium) and H₃R^3- (titanium)