POTENTIOMETRIC STUDY OF ACETATE COMPLEXES OF LANTHANUM(III)

The stability constants of La(III) - acetate complexes in aqueous medi um were determined by a potentiometric method, using a glass electrode , at (25.0 +/- 0. 1)degrees C and ionic strength 1.00 M (NaClO4). Four mononuclear stepwise complexes were detected with the Leden's graphic al method. Matrix solutions of weighted simultaneous equations with Fr onaeus function data lead to the following overall stability constants : beta(1) = (34.4 +/- 0.1) L.mol(-1), beta(2) = (274 +/- 1) L(2).mol(- 2), beta(3) = (464 +/- 5) L(3).mol(-3), beta(4) = (1.93 +/- 0.03)x10(3 ) L(4).mol(-4). A marked increase in affinity for the fourth acetate s pecies suggests a change of configuration after the third species.