The Aging Effect in the Mobility of Positive Ions.

volume very much less than under changes of temperature at constant pressure. He finds an expression for (n/br) in terms of the compressibility and the velocity of sound in the substance. Tested against the data of this paper this expression fails by a factor which may amount to thousands of fold. The very large pressure effects, the great variability of the pressure effect with the nature of the material, and the fact that the pressure effect is high in substances with complicated molecules suggests that there may be a very important element which is neglected in the usual explanations of the viscosity of liquids, namely an actual interlocking effect between the molecules. A complicated molecule may be thought to have geometrical projections which interfere with its free motion with respect to its neighbors. The restraint offered by such an interlocking will evidently be decreased by rising temperature, even at constant volume, and would be expected to be increased to a smaller or a very large extent (depending on the particular geometrical configuration) by decreases of volume under increasing pressure. 1 H. P. Phillips, these PROCUEDINGS, 7, 172-177 (1921). 2 L. Bri11ouin, Jour. Phys. Rad. (VI), 3,326-340,362-383 (1922).