Diffusion and Soret in Ternary Mixtures. Preparation of the DCMIX sub(2) Experiment on the ISS

• Published in: Microgravity science and technology Vol. 25; no. 5; pp. 275 - 283
• Main Authors: Shevtsova, Valentina, Santos, Cecilia, Sechenyh, Vitaliy, Legros, Jean Claude, Mialdun, Aliaksandr
• Format: Journal Article
• Language: English
• Published: 01-02-2014
• Subjects: Density; Diffusion; Diffusion coefficient; International Space Station; Microgravity; Miscibility gap; Sealing; Soret coefficient
• ISSN: 0938-0108; 1875-0494
• DOI: 10.1007/s12217-013-9349-6

We report on ground-based studies in course of preparation of the experiment DCMIX sub(2) (Diffusion coefficient in mixtures) to be performed on the International Space Station (ISS). In microgravity experiment the diffusion and thermodiffusion coefficients will be measured at six points with different compositions of the ternary mixture Toluene-Methanol-Cyclohexane. This mixture attracts attention of the researchers, as it has a miscibility gap and presumably large region with negative Soret coefficients. By using Optical Digital Interferometry we have measured the variations of refractive index Delta n in the full parameter space of concentrations. The regions of stable and unstable behavior of system were determined from the time-dependent behavior of Delta n. The system is hydrodynamically unstable in a wide region of compositions where Soret measurement should be done in microgravity. We present the results of the study of the compatibility of this mixture with often used sealing materials:Viton (R), Chemraz (R) and different types of Kalrez. To facilitate the expected theoretical studies we have measured density and thermal expansion in the points of the interest.