Energy of the Crystalline Lattice and Sound Velocity of Lanthanide Chlorides in Aqueous T-Butanol

The ultrasonic velocity of lanthanide chlorides in aqueous t-butanol has been determined, using a single-crystal interferometer at 25, 30, 35 and 40\degree C. The velocities are accurate to ± 0.003 %. The velocity data are correlated with lattice energies of the substances on the basis of Kudriavtsev's theory. The agreement between the calculated and experimental values is good at low concentration (C = 0.03 mole/liter) of electrolytes containing structure-breaking ions, while it becomes poor with a further increase in concentration. The discrepancy is believed to be due to the invalidity of the theory in the case of higher valance electrolytes, such as rare-earth chlorides. It has been observed that, almost at any concentration, the apparent lowering of velocity is in the order of gadolinium chloride > samarium chloride > neodymium chloride, while lanthanum chloride > neodymium chloride at low concentration and is reversed as the concentration increases. The results are discussed in the light of the structure breaking property of the ions studied.