Extraction-spectrophotometric investigations on two ternary ion-association complexes of gallium(III)

Complex formation and liquid-liquid extraction were studied in systems containing Ga(III), azoderivative of resorcinol {4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR)}, 2,3,5-triphenyltetrazolium chloride (TTC), water and chloroform. The optimum conditions w.r.t. pH, extraction time, concentration of ADR and concentration of TTC for the extraction of Ga(III) as an ion-associate complex were found.. The composition of the extracted complexes, (TT⁺)Ga(PAR)₂] (I), (TT⁺)Ga(TAR)₂] (II) or (TT⁺)₂Ga(OH)(TAR)₂] (III), and the constants of association (β) between 2,3,5-triphenyltetrazolium cation (TT⁺) with corresponding anionic chelates were established by several methods. The constants of distribution (K_D) and extraction (K_ex) of the principal species I and III were determined as well. The apparent molar absorptivities of the chloroform extract at the optimum extraction-spectrophotometric conditions were ɛ′₅₁₀=9.5×10⁴ L mol⁻¹ cm⁻¹ (I) and ɛ′₅₃₀=4.6×10⁴ L mol⁻¹ cm⁻¹ (III). The validity of Beer’s law was checked and analytical characteristics that were calculated are reported herein.