Die physikalisdie Deutung des molaren Sdiallvolumens und der darin enthaltenen Raosdien Regel

A critical reviews is given on the use of RAO'S expression u1/a V (“molar velocity of sound”). In continuation of an earlier investigation it is shown that RAO'S expression is part of a certain volume called “molar sound volume”. The molar sound volume is equal to the product of the radius of the molecule and the cross-section of the unit cell. The collision coefficient, which is of great significance in the propagation of sound is contained in the molar sound volume. It is shown that with decreasing temperature the collision coefficient approximates to the ideal value of 4 at absolute zero. The additivity of RAO'S expression from atomic increments is poor; this is in contrast to the good additivity of the molecular volume per mole. “Molar velocity of sound" is not an independent quantity of physical significance.