Experimental Investigation of Relaxation Processes Arising When Ultrasonic Waves Pass through Liquids

The article describes relaxation processes in acetates and formiates found experimentally. The investigation was carried on by impulse and optical methods at frequencies 1–30 Mc. In the interval of temperatures from −40°C to +30°C in methyl acetate, athyl acetate, methyl formiate, and athyl formiate, two complete regions of relaxation are found in every substance. In athyl acetate an investigation of ultrasonic waves absorption along the line of saturation was carried on, including critical and supercritical regions: one in the interval of temperatures 160°–210°C, the other in the critical region of the liquid phase of athyl acetate. For every relaxation region the time of relaxation and frequencies corresponding to the centre of relaxation were determined and volumetric viscosity of thermal capacity, relating to internal and external degrees of freedom and heats of activation were calculated. In conclusion, possible mechanisms of experimentally established relaxation processes are discussed.