The aqueous solution behavior of some rare-earth chlorides has been investigated at 25° C. in the concentration range between 0.02 molal and saturation. Density measurements on solutions of lanthanum, neodymium, samarium, gadolinium, dysprosium, erbium, and ytterbium chlorides were carried out by a pycnometric method with an estimated accuracy of 1 x 10-5 gm.per ml. From the density data the apparent molal volumes for these rare-earth chlorides were calculated. The apparent molal volume data for each rare-earth chloride were expressed as a function of the square root of the molality by a five-parameter power series from which partial molal volumes were calculated. Conductance measurements on solutions of these rare-earth chlorides were carried out over the same concentration range using the conventional alternating-current technique. In addition, the solubilities of the rare-earth chlorides at 25° c. were determined.