Application of 4,5,6-trihydroxy-9-phenylfluorones as analytical reagents

A system allowing the flotation condensation of inidium as its complex with gallein has been worked out. Benzene was used as a floating solvent. The effect of pH as well as those of the complexing agent concentration and a neutral electrolyte were studied and the optimum conditions for the reaction (pH approximately equal to 5) have been found. The metal-to-ligand molar ratio (1:1) and the number of protons exchanged by indium atom during the complexation (n=2) have been determined. The flotation-spectrophotometric method of indium-trace determination has been elaborated. Molar absorptivity of this complex in DMSO solution is equal to 3.104 and Λsub(max) is 540 nm. The method is very convenient since its blank test has the zero value. The effect of foreign ions was also studied and low selectivity of the method was stated. (author)