Measurements of the osmotic pressure in liquid mixtures of /sup 3/He and /sup 4/He near the lambda line and tricritical point

Technical Report · Wed Jun 01 04:00:00 EDT 1977

OSTI ID:5243744

Gearhart, Jr, C A

Values of the concentration susceptibility near the lambda line and tricritical point in liquid mixtures of /sup 3/He and /sup 4/He have been calculated from measurements of osmotic pressure differences. Measurements were made by inducing a small /sup 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 /sup 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 /sup 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 ..cap alpha.. = 0 both above and below the lambda transition except at x = 0.64, where some combination of ..cap alpha.. and ..cap alpha..' greater than zero seems to be preferred. (The result ..cap alpha.. = 0 corresponds to a logarithmic divergence.) It is possible that this positive value of ..cap alpha.. or ..cap alpha..' represents the influence of tricritical effects. It should be emphasized that there is considerable ambiguity in our determination of ..cap alpha.., with acceptable least-squares fits corresponding to values of ..cap 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.

• Research Organization: Minnesota Univ., Minneapolis (USA)
• DOE Contract Number: EY-76-S-02-1569
• OSTI ID: 5243744
• Report Number(s): TID-27646; E-1569-143
• Country of Publication: United States
• Language: English

Related Subjects

640460* -- Fluid Physics-- Other Quantum Fluids
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
DISPERSIONS
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FLUIDS
HELIUM 3
HELIUM 4
HELIUM ISOTOPES
ISOTOPES
LAMBDA POINT
LIGHT NUCLEI
LIQUIDS
MIXTURES
NUCLEI
OSMOSIS
PHYSICAL PROPERTIES
QUANTITY RATIO
STABLE ISOTOPES
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION TEMPERATURE