Yttrium and rare earth element complexation by chloride ions at 25°C

Formation constants for yttrium and rare earth element (YREE) chloride complexation have been measured at 25 degreesC by examining the influence of medium (NaClO4 and NaCl) on YREE complexation by fluoride ions and methyliminodiacetate (MIDA). YREE chloride complexation constants (Cl)beta (1) (M) obtained in this work using dissimilar procedures are in good agreement and indicate that, at constant temperature and ionic strength, (Cl)beta (1) (M) does not vary significantly across the fifteen-member series of elements. The ionic strength tt dependence of YREE chloride formation constants between 0 and 6 molar ionic strength can be written, for all YREE. as log (Cl)beta (1) (M) = log (Cl)beta (o)(1) (M) - 3.066 mu (0.5)/(1+1.727 mu (0.5)) where (Cl)beta (1) (M) = [MCl2+][M3+](-1)[Cl-1](-1) and log (Cl)beta (o)(1) (M) represents the MCl2+ formation constant for all YREE at zero ionic strength: log (Cl)beta (o)(1) = 0.65 +/-0.05.