MEASUREMENTS OF AL(NO3)3 ACTIVITIES IN AQUEOUS NITRATE SOLUTIONS

Aluminum nitrate activity coefficients obtained by vapor pressure osmo metry are compared with activity coefficients derived from nitric acid extraction measurements and Bromley's correlation. This solvent extra ction approach was possible because of the poor extraction of Al3+ (di stribution ratio less-than-or-equal-to 10(-3)) by the chosen solvents. The solvents compositions were 0.25M CMPO (octyl(phenyl)-N,N-diisobut ylcarbamoyl methylphosphine oxide) in tetrachloroethylene (TCE) and 0. 25M CMPO with 0.75M tributyl phosphate (TBP) in TCE. In both approache s, nitric acid was used to supress the hydrolysis of Al3+. At high ion ic strengths, the two techniques yielded very similar activity coeffic ients for Al(NO3)3. However, at intermediate and very low ionic streng ths, the two procedures produced considerably different activity coeff icients.