ALUMINUM SPECIATION AND EQUILIBRIA IN AQUEOUS-SOLUTION .4. A POTENTIOMETRIC STUDY OF ALUMINUM ACETATE COMPLEXATION IN ACIDIC NACL BRINES TO 150-DEGREES-C

The molal formation quotients for Al(Ac)(n)(3-n) were measured potentiometrically from 25 to 150 degrees C at ionic strengths of 0.1, 0.2, 0.3, 0.6, and 1.0 mol kg(-1) in an aqueous NaCl medium. The titrations were carried out over the pH range 1.9 to 3.1 in a hydrogen-electrode, concentration cell. Aluminum acetate species with values of ligand number, ($) over bar n, from one to three were detected, although the stability fields in which they represented a significant fraction of the total aluminum were limited to restricted conditions of temperature and ionic strength. Two empirical equations were formulated containing four adjustable parameters to describe the temperature and ionic strength dependencies of the formation equilibrium quotients for Al(Ac)(2+) and Al(Ac)(2)(+). Limited thermodynamic data are presented for the Al(Ac)(3) degrees species. Comparisons are made with the limited thermodynamic information available in the literature.