Excess volume of an equimolar 3He–4He mixture

The molar volume of a 3He–4He mixture with 50.7% 3He has been determined by measurements of the dielectric permittivity. Measurements were made along isotherms in the pressure interval 0.3–25 atm at temperatures in the range 4.2–14°K as well as along isobars at pressures ranging from 1.0 to 16 atm. The excess volume VE, by which the molar volume of the mixture exceeds the ideal value, was determined as a function of temperature and density. It was found that this function has a complicated sign-alternating character. Calculations of the excess volume based upon the theory of Prigogine are presented, and it is shown that this theory exhibits quantitative agreement with the experiment. A small deviation between the experimental and theoretical values of VE arising at large densities is connected with the appearance of quantum statistical effects.