Abstract
We describe an instrument for the measurement of the Soret and thermodiffusion coefficients in ternary systems based on the transient holographic grating technique, which is called Soret forced Rayleigh scattering (SFRS) or thermal diffusion forced Rayleigh scattering (TDFRS). We integrated the SFRS technique and the two-wavelength detection technique, which enabled us to obtain two different signals to determine the two independent Soret coefficients and thermodiffusion coefficients in ternary systems. The instrument has been designed to read the mass transport simultaneously by two-wavelength lasers with wavelengths of λ = 403 nm and λ = 639 nm. The irradiation time of the probing lasers is controlled to reduce the effect of laser absorption to the sample with dye (quinizarin), which is added to convert the interference pattern of the heating laser of λ = 532 nm to the temperature grating. The result of the measurement of binary benchmark mixtures composed of 1,2,3,4-tetrahydronaphthalene (THN), isobutylbenzene (IBB), and n-dodecane (nC12) shows that the simultaneous two-wavelength observation of the Soret effect and the mass diffusion are adequately performed. To evaluate performance in the measurement of ternary systems, we carried out experiments on the ternary benchmark mixtures of THN/IBB/nC12 with the mass fractions of 0.800/0.100/0.100 at a temperature of 298.2 K. The Soret coefficient and thermodiffusion coefficient agreed with the ternary benchmark values within the range of the standard uncertainties (23% for the Soret coefficient of THN and 30% for the thermodiffusion coefficient of THN).
Highlights
We describe an instrument for the measurement of the Soret and thermodiffusion coefficients in ternary systems based on the transient holographic grating technique, which is called Soret forced Rayleigh scattering (SFRS) or thermal diffusion forced Rayleigh scattering (TDFRS)
The first observation of thermodiffusion by this technique was reported by Thyagarajan and Lallemand on CS2-ethanol mixtures in 1978.6 Kohler et al significantly improved the transient holographic grating technique using heterodyne detection schemes, and their improved method is known as thermal diffusion forced Rayleigh scattering (TDFRS)
We have presented an experimental instrument based on the optical holographic grating technique, which we call the Soret forced Rayleigh scattering (SFRS) or thermal diffusion forced Rayleigh scattering (TDFRS), for the measurement of the Soret and thermodiffusion coefficients in ternary systems
Summary
Mass transport phenomena including thermodiffusion (or the Soret effect, Ludwig-Soret effect) play significant roles in many natural systems and engineering processes. Since there is as yet no comprehensive microscopic description of thermodiffusion in multicomponent liquid mixtures, both experimental and theoretical approaches are important for understanding and applications. The transient holographic grating technique is one of the experimental methods used to examine mass diffusion and thermodiffusion. The first observation of thermodiffusion by this technique was reported by Thyagarajan and Lallemand on CS2-ethanol mixtures in 1978.6 Kohler et al significantly improved the transient holographic grating technique using heterodyne detection schemes, and their improved method is known as thermal diffusion forced Rayleigh scattering (TDFRS). This technique has been employed in the investigation of various binary mixtures, including polymer solutions, polymer blends, isotopic systems, and aqueous solutions.. The first observation of thermodiffusion by this technique was reported by Thyagarajan and Lallemand on CS2-ethanol mixtures in 1978.6 Kohler et al significantly improved the transient holographic grating technique using heterodyne detection schemes, and their improved method is known as thermal diffusion forced Rayleigh scattering (TDFRS).. The first observation of thermodiffusion by this technique was reported by Thyagarajan and Lallemand on CS2-ethanol mixtures in 1978.6 Kohler et al significantly improved the transient holographic grating technique using heterodyne detection schemes, and their improved method is known as thermal diffusion forced Rayleigh scattering (TDFRS).4,7,8 This technique has been employed in the investigation of various binary mixtures, including polymer solutions, polymer blends, isotopic systems, and aqueous solutions.. The standard uncertainties of the Soret coefficient and the thermodiffusion coefficient based on the Guide to the Expression of Uncertainty in Measurement (GUM) are shown with the experimental data
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