ISSN:
1089-7690
Quelle:
AIP Digital Archive
Thema:
Physik
,
Chemie und Pharmazie
Notizen:
We report turbidity, light scattering, and coexistence curve data for a solution of triethyl n-hexyl ammonium triethyl n-hexyl borate in diphenylether. We recently reported that the present sample shows much higher turbidity than that of K. S. Zhang, M. E. Briggs, R. W. Gammon, and J. M. H. Levelt Sengers [J. Chem. Phys. 109, 4533 (1998)] for an earlier sample. An analysis of the data shows that nonclassical critical behavior is favored in the reduced temperature range from 10−5 to 10−2. At fixed reduced temperature, the correlation length is about twice as large as that of the previous sample. The correlation length amplitude calculated from the fit is 1.4 nm±0.1 nm. A detailed data analysis points out the limitations of turbidity measurements far away from the critical point. The intensity of scattered light was measured at 90°. Multiple scattering is relevant in the wider vicinity of the critical point and was corrected for by a Monte Carlo simulation method. An Ising-type exponent for the correlation length was obtained: ν=0.641±0.003, and the amplitude of the correlation length ξ0=1.34 nm±0.01 nm agrees with that of the turbidity experiment. Mean-field behavior can be ruled out. The refractive indices of coexisting phases were measured in the reduced temperature range from t=10−4 to 0.04. These measurements disagree with results reported by R. R. Singh and K. S. Pitzer [J. Chem. Phys. 92, 6775 (1990)]. The present data lead to an exponent β=0.34±0.01, close to the Ising value. The coexistence curve is much narrower than that of Singh and Pitzer. Crossover could not be detected in any of the experiments. Two-scale-factor universality could be confirmed for this and another ionic system within the experimental uncertainty. © 1998 American Institute of Physics.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1063/1.477574
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