167 Geochemistry

Tuesday, 18 October 2005
1:30 PM - 5:30 PM

ASSOCIATION QUOTIENTS OF ALUMINUM OXALATE COMPLEXES IN AQUEOUS SOLUTIONS

Paper number: 167-3
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

Although a number of measurements of the association quotients of Al-oxalate species have been made at 25°C, relatively few measurements exist at higher and lower temperatures. To assess the significance of Al-oxalate speciation in geological systems we have measured equilibria of the form

Al3+ + nC2O42- = Al(C2O4)n3-2n n≤3

Formation constants were measured by potentiometric titration using a hydrogen electrode concentration cell. Measurements were made at 8 temperatures ranging from 5 to 150°C and at ionic strengths ranging from 0.1 mol-kg-1 to 1.0 mol-kg-1 in aqueous NaCl media. When I=0.6 mol-kg-1, the values of Q1, Q2, and Q3 increase from 105.33, 109.87, and 1014.12, respectively, at 5°C to 107.41, 1012.76, and 1016.94, respectively, at 125°C. Values of Q1, Q2, and Q3 at 25°C and I=0.6 mol-kg-1 are in good agreement with those published previously after recalculation using more recent values of the dissociation of oxalic acid.