抄録
The molecular sound velocity of Rao R=M⁄ρ·V1⁄3 and the molecular compressibility introduced by Wada B=M⁄ρ·β−1⁄7 (=M⁄ρ6⁄7·V2⁄7), where M means the molecular weight, ρ the density, V the sound velocity and β the adiabatic compressibility, have been computed for 37 mixtures of mutually soluble liquids employing existing ultrasonic velocity data and the number average molecular weights. Although the sound velocity in and the adiabatic compressibility of liquid mixtures are known to be not necessarily monotonous functions of the concentration, exhibiting maxima or minima in some cases, the molecular compressibilities were found to be linear functions of concentration (molar fraction) in most of the liquids examined. The molecular sound velocities were found to be linear functions of the molar fraction in many of the mixtures, but they deviated from straight lines and became concave upwards in mixtures consisting of one heavy component (such as carbon tetrachloride and chloroform) and one light component. Both R and B, however, failed to be linear functions of molar fraction in water-alcohol mixtures, slightly deviating upwards from the straight lines with maxima of deviation in the neighbourhood of the concentrations corresponding to the velocity maxima. A few mixtures showed irregular R- and B-curves. This is presumably attributable to the inaccuracy of velocity data employed.
