The effect of rare-earth chlorides on the structure of water has been investigated at low concentrations by determining the ultrasonic velocity and density at several temperatures around temperatures corresponding to adiabatic compressibility minimum (TACM) and sound velocity maximum (TSVM) of water. Ultrasonic velocity is determined with an accuracy of ±0.003% using single crystal variable path interferometer and densities to an accuracy of ±0.002% using Pycnometer. The results are discussed in the light of structure breaking or structure making of the Rare-Earth chlorides in water.