Theory of Ultrasonic Thermal Relaxation Times in Liquids

The theory of thermal relaxation phenomena in liquids is considered from the standpoint that the mechanism of energy transfer in the liquid is the same as in a gas. This would mean that binary collisions and not cooperative action of the molecules are important. The data on ultrasonic relaxation in CS2 is considered. It is found that values predicted by use of the cell model, proposed for liquids and dense gases, in combination with binary collision theory give values for the pressure and temperature dependence of ultrasonic relaxation times which are in good agreement with experiment. Furthermore excellent agreement is found between the values of the probability of energy transfer per collision found in the liquid and gaseous CS2. It also appears that the Schwarz‐Herzfeld theory which has been applied to gases can also be applied to liquids and dense gases. It is concluded that the mechanism of energy transfer in thermal relaxation is not affected by the change in state from gas to liquid.