The binary system triethylamine-water near its critical consolute point: An ultrasonic spectrometry, dynamic light scattering, and shear viscosity study
2002 | journal article. A publication of Göttingen
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The binary system triethylamine-water near its critical consolute point: An ultrasonic spectrometry, dynamic light scattering, and shear viscosity study
Behrends, R.; Telgmann, T. & Kaatze, U. (2002)
The Journal of Chemical Physics, 117(21) pp. 9828-9837. DOI: https://doi.org/10.1063/1.1517609
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Details
- Authors
- Behrends, Ralph; Telgmann, T.; Kaatze, Udo
- Abstract
- Ultrasonic attenuation spectra between 100 kHz and 500 MHz, mutual diffusion coefficients and shear viscosities of the triethylamine/water mixture of critical composition have been measured at various temperatures near the critical one. The broadband ultrasonic spectra reveal two relaxation terms with discrete relaxation time and a term that is subject to a broad relaxation time distribution. The former have been discussed to be due to a protolysis reaction and a structural isomerization. The latter term has been evaluated in the light of the Bhattacharjee-Ferrell dynamic scaling theory, relating the sonic spectrum to fluctuations in the local mixture concentrations. The relaxation rate of the Bhattacharjee-Ferrell term follows power law behavior. However, its amplitude (Gamma(0)=45x10(9) s(-1)) is considerably smaller than that derived from the dynamic light scattering and shear viscosity measurements (Gamma(0)=96x10(9) s(-1)). This result is assumed to be due to a shear viscosity relaxation. Using density and heat capacity measurements from the literature, the adiabatic coupling constant g of the triethylamine/water system has been derived from the amplitude of the Bhattacharjee-Ferrell term in the ultrasonic spectra and from a thermodynamic relation as well. Again, a discrepancy is found. The ultrasonic spectra yield g=0.19, whereas g=0.98 follows otherwise. This difference in the g values is taken as an indication of the limitations of the Bhattacharjee-Ferrell model. It had been derived assuming a small amplitude in the singular part of the heat capacity, a precondition which is clearly not fulfilled with the triethylamine/water system. (C) 2002 American Institute of Physics.
- Issue Date
- 2002
- Status
- published
- Publisher
- Amer Inst Physics
- Journal
- The Journal of Chemical Physics
- ISSN
- 0021-9606