Optical techniques were used to study the critical behaviour of the pure fluids CHF₃, CCIF₃ and Xe, and binary mixtures He-Xe and nicotine + water. We find that for all these substances, the order parameter is described by a power law in the reduced temperature t = (Tc - T)/Tc with a leading exponent β = 0.327 ± 0.002. Also, we determine the first correction to scaling exponent to be Δ = 0.43 ± 0.02 for the pure fluids and Δ = 0.50 ± 0.02 for the He-Xe system.
The coexistence curve diameter in CHF₃ and CCIF₃ exhibits a deviation from rectilinear
diameter, in agreement with a modern theory which interprets this behaviour as resulting from three-body effects. In contrast, no such deviation is observed in Xe where, according to that theory, it should be more pronounced than in other substances.
In the polar fluid CHF₃, the order parameter, isothermal compressibility and the chemical potential along the critical isotherm were simultaneously measured in the same experiment in an effort to ensure self-consistency of the results. From the data, two amplitude ratios which are predicted to be universal are determined: Γ+⃘ /Γ-⃘= 4.8 ± 0.6 and D⃘Γ+⃘B⃘δ-₁ = 1.66 ± 0.14.
In the binary liquid system nicotine + water, the diffusivity was measured both by light scattering and by interferometry. The results agree qualitatively, but differ by a factor of ≈ 2. From the light scattering data, the critical exponent of the viscosity is found to be zη = 0.044 ± 0.008.
The interferometric experiments on Xe and He-Xe furnish a direct way to maesure the effects of wetting: From the data, the exponent of the surface tension is found to be n = 1.24 ± 0.06. The similarity of the order parameter and compressibility in Xe and a He-Xe mixture containing 5% He indicate that the phase transition in this He-Xe mixture is of the liquid-gas type rather than the binary liquid type. / Science, Faculty of / Physics and Astronomy, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/30786 |
| Date | January 1990 |
| Creators | Närger, Ulrike |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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