The Study of the Molecular Structure of Organic Liquids by Means of Ultrasonics

Abstract

A modified resonance and reverberation technique has been developed for the measurement of ultrasonic absorption in liquids from about 1 megacycle per second down to below 20 kilocycles per second, the limits being a function of the absorption. A spherical container is calibrated with a carefully chosen set of liquids by using the extrapolated values of absorption coefficients which have been obtained at higher frequencies by the pulse technique. The calibrated container can then be used to measure the absorption in an unknown liquid, the calibration curves being used to give the true value of the liquid's absorption (i.e., less the container wall effect). The significant features of this technique are that only one container is necessary, the nature of the container reduces the possibility of contaminating the liquid to a minimum, and quantities of liquid as small as 5 milliliters can be studied. Over 40 liquids have been measured. Hitherto unknown relaxation phenomena have been observed in 12 liquids. A mechanism which accounts for the relaxation processes is proposed.