Measurement of the acoustic nonlinearity parameter B/A in solvents: Dependence on chain length and sound velocity

Abstract

This work consists of a systematic study of the acoustic nonlinearity parameter (B/A) in 1-alkanols from methanol to 1-decanol, ketones from acetone to methyl hexyl ketone, and alkyl acetates from ethyl to octyl acetate. By focusing a 14-MHz tone burst through a spherical quartz lens in each solvent, the second harmonic is generated and measured by a 28-MHz transducer at various distances from the focus. This provides the point of maximum second harmonic power, and enables the computation of the nonlinear parameter using a simple model. The B/A values thus obtained are in reasonable agreement with these available in the literature. The B/A values are found to increase with chain length and sound velocity, this increase being in contradiction with Ballou’s rule. Moreover, a hybrid model based on Schaaffs’ formula for sound velocity fits the experimental results, questioning the validity of Ballou’s rule for solvents within a single chemical family.