Determination of formation constants of hydroxo carbonate complexes of Pr3+ in 2M NaCl at 303 K

The hydrolysis of Praseodymium III in 2M sodium chloride at 303 K was studied. Two methods were used: pH titration followed by a computational refinement and solvent extraction in the presence of a competitive ligand. The hydrolysis constants obtained by pH titration were: log β1,H = -7.68 ± 0.07, log β1,2H = -15.10 ± 0.03, and β1,3H -23.8 ± 0.04. The stability constants of Praseodymium carbonates were determined by pH titration as well and were: log β1,CO32- = 5.94 ± 0.08 and log β1,2CO32- = 11.15 ± 0.15. Praseodymium carbonate species were taken into consideration for calculating the first hydrolysis constants by the solvent extraction method and the value obtained was: log β1,H = -7.69 ± 0.27. The values for log β1,H attained by both methods are the same. The species-distribution diagram was obtained from the stability constants of Praseodymium carbonates and hydrolysis products in the conditions of the present work. (Author)