ELECTROANALYTICAL STUDY OF ALUMINUM FLUORIDE COMPLEXATION IN 2-PROPANOL-WATER MIXTURES

Theoretical approaches to aluminum-ion determination by two potentiome tric methods (potentiometric titration and analyte subtraction potenti ometry) are discussed. The computed theoretical titration curves show that the equivalence point is signaled by a sufficiently large change in the potential only in media where aluminum forms a hexafluoride com plex; the overall formation constant of this complex is beta(AlF63-)gr eater than or equal to 10(28). On the basis of the potentiometric titr ation and the known subtraction experiments in 2-propanol-water, buffe red with acetate buffer (pH 5), the overall conditional constants (bet a') were calculated. The calculated average beta'-values are 10(31) an d 10(33), depending on the vol% of organic solvent, 50% and 67%. In th e mixtures having a vol% of organic solvent of 50% or 67%, both method s can be applied for the determination of aluminum, via AlF63- complex formation, in the concentration range from 10(-4) to 10(-3) M.