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Optical studies of critical phenomena in fluids Fameli, Nicola
Abstract
Accurate optical techniques were employed to study the behaviour of the binary liquid mixture n-heptane+nitrobenzene (C₇H₁₆ + C₆H₅NO₂) and of the pure fluid 1,1-difluoroethylene (C₂H₂F₂) near their respective critical regions. It is found that, in the region of reduced temperature, t = (T[sub c] — T)/T[sub c] < 3 x 10 ⁻⁴ , the order parameter ΔΦ[sub H] for the binary mixture follows a power law ΔΦ[sub H]« t[sup β], with a leading exponent β = 0.367 ± 0.006, which is higher than the predicted theoretical value of β = 0.326 ± 0.002. A careful study of the effect of refractive index gradients caused by the Earth's gravitational field, potential variation of the optical thickness of the sample cells due to wetting of the cell walls by one the phases, and the long thermal equilibration times of binary mixtures has failed to resolve the disagreement between β measured on n-heptane+nitrobenzene and its theoretical value. A significant feature of this investigation is the novel application of an optical technique (the image plane technique) for studying critical phenomena in transparent binary liquids. The Lorentz-Lorenz function, £, of 1,1-difluoroethylene was measured in order to determine the fluid's density from its refractive index. The quantity £. is found to vary by about 1.4% with density of the fluid, p, with a gentle maximum at a density slightly higher than the critical density, p[sub c]. The density measurements were then used to construct the coexistence curve for this material. The coexistence curve of C₂H₂F₂ was measured with the 'Lorentz-Lorenz' experiment and with a new apparatus combining two complementary optical methods, the prism cell technique and the focal plane technique, into one. The measurements carried out on C₂H₂F₂ in this thesis serve as a test of this apparatus. The order parameter data of C₂H₂F₂ are described accurately by a scaling power law in terms of the reduced temperature t, with the critical exponents at their theoretical values. The coexistence curve data^ taken simultaneously with the two combined techniques agree well with each over the whole range of temperature investigated.
Item Metadata
Title |
Optical studies of critical phenomena in fluids
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Creator | |
Publisher |
University of British Columbia
|
Date Issued |
2000
|
Description |
Accurate optical techniques were employed to study the behaviour of the
binary liquid mixture n-heptane+nitrobenzene (C₇H₁₆ + C₆H₅NO₂) and of
the pure fluid 1,1-difluoroethylene (C₂H₂F₂)
near their respective critical
regions.
It is found that, in the region of reduced temperature, t = (T[sub c] — T)/T[sub c] <
3 x 10 ⁻⁴ , the order parameter ΔΦ[sub H] for the binary mixture follows a power
law ΔΦ[sub H]« t[sup β], with a leading exponent β = 0.367 ± 0.006, which is higher
than the predicted theoretical value of β = 0.326 ± 0.002. A careful study
of the effect of refractive index gradients caused by the Earth's gravitational
field, potential variation of the optical thickness of the sample cells due to
wetting of the cell walls by one the phases, and the long thermal equilibration
times of binary mixtures has failed to resolve the disagreement between β
measured on n-heptane+nitrobenzene and its theoretical value. A significant
feature of this investigation is the novel application of an optical technique
(the image plane technique) for studying critical phenomena in transparent
binary liquids.
The Lorentz-Lorenz function, £, of 1,1-difluoroethylene was measured in
order to determine the fluid's density from its refractive index. The quantity
£. is found to vary by about 1.4% with density of the fluid, p, with a gentle
maximum at a density slightly higher than the critical density, p[sub c]. The
density measurements were then used to construct the coexistence curve for
this material.
The coexistence curve of C₂H₂F₂ was measured with the 'Lorentz-Lorenz'
experiment and with a new apparatus combining two complementary optical
methods, the prism cell technique and the focal plane technique, into one.
The measurements carried out on C₂H₂F₂ in this thesis serve as a test of this
apparatus. The order parameter data of C₂H₂F₂ are described accurately
by a scaling power law in terms of the reduced temperature t, with the
critical exponents at their theoretical values. The coexistence curve data^
taken simultaneously with the two combined techniques agree well with each
over the whole range of temperature investigated.
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Extent |
7374083 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-20
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Provider |
Vancouver : University of British Columbia Library
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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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DOI |
10.14288/1.0085498
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2000-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
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.