The molar volume and expansion coefficient of liquid He4

Abstract

The density of liquid He4 under its own vapor pressure has been measured over the range 0.5-2.8°K with a precision of about 0.006%. A direct pycnometric method was used; the cell was immersed in a liquid He3 bath. Detailed measurements in the neighborhood of the lambda point temperature showed the density maximum to occur 0.006°K above Tλ. Analysis of these data and other available data has yielded analytical equations from which the coefficient of expansion has been determined. Below 2.14°K the Landau formulations of He II was found to represent the data. In the neighborhood of Tλ the density changes logarithmically in |T - Tλ|. Above 2.2°K all available data are fitted as a function of the He4 vapor pressure. The behavior near Tλ is analyzed in terms of the theory of Buckingham and Fairbank. © 1964.