Lambda-Temperatures of Solutions ofHe3inHe4

Abstract

An expression for the effect of ${\mathrm{He}}^3$ on the lambda-point of ${\mathrm{He}}^4$ is developed from thermodynamic principles. Use is made of the idea that normal ${\mathrm{He}}^4$ and superfluid ${\mathrm{He}}^4$ are in equilibrium with each other and that the lambda-temperature is the temperature at which superfluid first appears. This expression contains the difference in enthalpy of normal fluid and superfluid. The lambda-points of mixtures containing large amounts of ${\mathrm{He}}^3$ are discussed on the basis of various assumptions regarding this difference in enthalpy as a function of temperature.