New Type of Freezing-Point Apparatus. Freezing Points of Dilute Lanthanum Chloride Solutions

A new type of freezing-point apparatus is described that reduces the errors of previous types. The freezing-point depressions of aqueous lanthanum chloride solutions up to 0.04 m are adequately expressed by the Debye-Hückel approximation for ions with a=6.15 A plus a very small linear term. The ``higher terms'' are computed by combining the equations of Mayer and Kirkwood, using the tables of Poirier, and are found to be very small in this case. The parameters for the calculation of the activity of water from freezing point depressions, for the Debye-Hückel theory, and for the Kirkwood parameter Bik are redetermined, and the more general use of Bik is discussed.