Ultrasonic absorption of nitrobenzene–isooctane mixtures of non-critical composition
Abstract
The dynamic scaling theory of Ferrell and Bhattacharjee (Phys. Rev. A, 1985, 31, 1788) has been used to analyse ultrasonic absorption data of two nitrobenzene–isooctane mixtures of non-critical composition. The measurements were carried out as a function of temperature [1 ⩽(T–Tp)/K ⩽ 20; Tp, temperature of phase separation] and frequency (3 ⩽f/MHz ⩽ 57). The data describing the temperature- and frequency-dependent contributions of composition fluctuations to the ultrasonic absorption follow a single curve. The data can be represented by a modified dynamic scaling function similar to that proposed by Ferrell and Bhattacharjee to describe the ultrasonic absorption of a mixture of critical composition. The temperature dependence of the scaling variable Ωnc for the mixtures of non-critical compostion is calculated by replacing the critical temperature Tc by an empirical pseudospinodal temperature Tps or the temperature of phase separation Tp of the mixture of non-critical composition. The frequency- and temperature-independent parameter ω0, nc of the scaling variable Ωnc is used as the only free parameter of the fit of the scaling function F(Ωnc) to the experimental data. The value of ω0 is found to be composition dependent.