Osmotic and activity coefficients of aqueous NaTcO4 and NaReO4 solutions at 25�C

Abstract

Isopiestic vapor-pressure comparison experiments were performed with aqueous binary sodium perchlorate, pertechnetate, and perrhenate solutions to concentrations of approximately 8.5 m. Osmotic coefficients for these solutions and mean molal ionic activity coefficients for NaTcO4 and NaReO4 were derived from the isotonic molalities. Pitzer's treatment was applied to describe the concentration dependence of the osmotic coefficients of NaClO4, NaTcO4, and NaReO4, and the implications of the parameters derived from a leastsquares fit are discussed in terms of solvent structure and interionic forces.