Second-sound velocity in superfluid 3He–4He solutions

The second-sound velocity was measured in superfluid 3He–4He solutions containing up to 13% 3He in the temperature range from 1.3°K to Tλ. Together with earlier experimental data, the results enabled us to construct the concentration dependence of the second-sound velocity in superfluid solutions. Comparison of the experimental values of the second-sound velocity with the results given by the theory of Khalatnikov1 showed good agreement.