ACTIVITY-COEFFICIENTS OF ELECTROLYTES FROM THE EMF OF LIQUID MEMBRANE CELLS .4. REVISED ACTIVITY-COEFFICIENTS OF LANTHANUM HEXACYANOFERRATE(III)

Lanthanum ferricyanide is so far the only 3-3 electrolyte whose activity coefficients have been studied carefully; however, the results have been acknowledged to be inconsistent below 1x10(-4) mol-kg(-1). New measurements have been made with an improved cell, proving that the wrong trend was due to chemical interference in the original cell. The new cell makes it possible to reach dilution levels of the order of 4x10(-6) mol-kg(-1). The salt behaves radically unlike Debye-Huckel's predictions, but agrees with other more refined treatments of the hard sphere models without needing any further hypotheses, such as e.g., association. The revised values of the activity coefficients are reported.