Hydroxide complexes of lanthanides-IV ytterbium(III) in perchlorate medium

From the precipitation borderline in the pM'-pC(H) diagram, determined experimentally under CO(2)-free conditions, the stability constants of the mononuclear species of ytterbium hydroxide have been established. The values found are log *beta(1) = -7.7, log *beta(2) = -15.5, log *beta(3) = -23.2, log *beta(4) = -37.5, log *beta(5) = -51.9, log *beta(6) = -66.2 and log *K(S0) = 18.0. The data refer to fresh precipitates, prepared at room temperature (21.5 +/- 0.2 degrees ) in sodium perchlorate medium with an ionic strength of 1. The formation of polynuclear hydroxide complexes has been considered and rejected as unlikely to occur.