MODEL OF SHORT-RANGE ORDER IN A CONCENTRATED LACL3 AQUEOUS-SOLUTION FROM X-RAY-DIFFRACTION STUDIES

A concentrated aqueous solution of LaCl3 has been investigated by the X-ray diffraction method. The main features of the pair function are consistent with the presence of the [La(H2O)9Cl2]+ complex additionally hydrated in the second sphere. The outer-sphere Cl- ions are hydrogen bonded to the inner-sphere water molecules. The La3+-Cl- distance points either to a trigonal orientation of inner-sphere water molecules and the hydrogen bond angle of 170-degrees or to the tilt angle of 30-degrees and a linear hydrogen bond.