Adiabatic Coupling Constant of Nitrobenzene-n-Alkane Critical Mixtures. Evidence from Ultrasonic Spectra and Thermodynamic Data

作者：Mirzaev Sirojiddin Z; Kaatze Udo^*

来源：International Journal of Thermophysics, 2016, 37(9): 89.

DOI：10.1007/s10765-016-2095-4

• Adiabatic coupling constant
• Binary liquids
• Critical demixing
• Dynamic scaling
• Ultrasonic spectroscopy

Ultrasonic spectra of mixtures of nitrobenzene with n-alkanes, from n-hexane to n-nonane, are analyzed. They feature up to two Debye-type relaxation terms with discrete relaxation times and, near the critical point, an additional relaxation term due to the fluctuations in the local concentration. The latter can be well represented by the dynamic scaling theory. Its amplitude parameter reveals the adiabatic coupling constant of the mixtures of critical composition. The dependence of this thermodynamic parameter upon the length of the n-alkanes corresponds to that of the slope in the pressure dependence of the critical temperature and is thus taken another confirmation of the dynamic scaling model. The change in the variation of the coupling constant and of several other mixture parameters with alkane length probably reflects a structural change in the nitrobenzene-n-alkane mixtures when the number of carbon atoms per alkane exceeds eight.

• 出版日期2016-9