Experimental study of the equation of state of helium isotopes (4He and 3He) over the temperature range from 3.3°K to 14°K

The P-V-T relations for the helium isotopes 3He and 4He are studied experimentally by the method of determining the dielectric constant of the substances in a UHF cavity resonator. The measurements are conducted in the temperature ranges from the critical points of the isotopes up to ∼ 14°K, which have not previously been investigated practically. For 3He and 4He, measurements of the molar volumes are made along 11 isotherms and 6 isobars. The data obtained about the equations of state of the helium isotopes are found to be in good agreement with the results available in the literature for adjoining temperature regions. Our results for 4He are found to be in satisfactory agreement with the only known measurements of Hill and Lounasmaa in the temperature range investigated.