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Measurements of the Osmotic Pressure in Liquid Mixtures of exp 3 He and exp 4 He Near the lambda Line and Tricritical Point.

TID27646

Publication Date	1977
Personal Author	Gearhart, C. A.
Page Count	215
Abstract	Values of the concentration susceptibility near the lambda line and tricritical point in liquid mixtures of exp 3 He and exp 4 He have been calculated from measurements of osmotic pressure differences. Measurements were made by inducing a small exp 3 He mole fraction difference delta x between two chambers separated by a pressure transducer, and measuring the resulting osmotic pressure difference as a function of temperature. Osmotic equilibrium was established through a Vycor glass superleak, which for exp 3 He mole fraction x > 0.55 functions not only in the superfluid phase but in portions of the normal fluid region of the phase diagram as well. Measurements were made at four exp 3 He mole fractions, x = 0.59, x = 0.64, x = 0.68, and x = 0.70. In contrast with determinations from light scattering and vapor pressure measurements, the present measurements show a pronounced peak at the lambda transition for the two values of x less than the tricritical value (x/sub t/ = 0.675). The susceptibilities are consistent with alpha = 0 both above and below the lambda transition except at x = 0.64, where some combination of alpha and alpha ' greater than zero seems to be preferred. (The result alpha = 0 corresponds to a logarithmic divergence.) It is possible that this positive value of alpha or alpha ' represents the influence of tricritical effects. It should be emphasized that there is considerable ambiguity in our determination of alpha , with acceptable least-squares fits corresponding to values of alpha between 0.0 and 0.2 being found at both concentrations, both above and below T/sub lambda/. The results appear to be consistent with the results of other experiments away from the lambda line, and also to be consistent with a simple tricritical scaling relationship. (ERA citation 03:022324)
Keywords	Helium 3 Helium 4 Lambda point Mixtures Osmosis Quantity ratio Temperature dependence ERDA/640460 Liquid helium
Source Agency	Technical Information Center Oak Ridge Tennessee
NTIS Subject Category	46 - Physics
Corporate Authors	Minnesota Univ., Minneapolis.; Department of Energy.
Supplemental Notes	Thesis.
Document Type	Technical Report
NTIS Issue Number	197814
Contract Number	EY-76-S-02-1569

Measurements of the Osmotic Pressure in Liquid Mixtures of exp 3 He and exp 4 He Near the lambda Line and Tricritical Point.

Measurements of the Osmotic Pressure in Liquid Mixtures of exp 3 He and exp 4 He Near the lambda Line and Tricritical Point.
TID27646

Publication Date	1977
Personal Author	Gearhart, C. A.
Page Count	215
Abstract	Values of the concentration susceptibility near the lambda line and tricritical point in liquid mixtures of exp 3 He and exp 4 He have been calculated from measurements of osmotic pressure differences. Measurements were made by inducing a small exp 3 He mole fraction difference delta x between two chambers separated by a pressure transducer, and measuring the resulting osmotic pressure difference as a function of temperature. Osmotic equilibrium was established through a Vycor glass superleak, which for exp 3 He mole fraction x > 0.55 functions not only in the superfluid phase but in portions of the normal fluid region of the phase diagram as well. Measurements were made at four exp 3 He mole fractions, x = 0.59, x = 0.64, x = 0.68, and x = 0.70. In contrast with determinations from light scattering and vapor pressure measurements, the present measurements show a pronounced peak at the lambda transition for the two values of x less than the tricritical value (x/sub t/ = 0.675). The susceptibilities are consistent with alpha = 0 both above and below the lambda transition except at x = 0.64, where some combination of alpha and alpha ' greater than zero seems to be preferred. (The result alpha = 0 corresponds to a logarithmic divergence.) It is possible that this positive value of alpha or alpha ' represents the influence of tricritical effects. It should be emphasized that there is considerable ambiguity in our determination of alpha , with acceptable least-squares fits corresponding to values of alpha between 0.0 and 0.2 being found at both concentrations, both above and below T/sub lambda/. The results appear to be consistent with the results of other experiments away from the lambda line, and also to be consistent with a simple tricritical scaling relationship. (ERA citation 03:022324)
Keywords	Helium 3 Helium 4 Lambda point Mixtures Osmosis Quantity ratio Temperature dependence ERDA/640460 Liquid helium
Source Agency	Technical Information Center Oak Ridge Tennessee
NTIS Subject Category	46 - Physics
Corporate Authors	Minnesota Univ., Minneapolis.; Department of Energy.
Supplemental Notes	Thesis.
Document Type	Technical Report
NTIS Issue Number	197814
Contract Number	EY-76-S-02-1569