Entropy of the Superfluid Component of Helium

The specific entropy deficit $\Delta s=s-s_s$ of the superfluid component of liquid helium II has been determined over the temperature range 1.27°K to 1.93°K. Here $s$ and $s_s$ are the specific entropy of the bulk liquid and of the superfluid component, respectively. Superfluid was transferred into a thermally isolated reservoir from a constant temperature reservoir by film flow. Values of $\Delta s$ were determined from flow rates obtained by driving the film by thermal means. Flow rates were measured with a capacitor death gauge. The present results indicate that $\Delta s=s$ within ± 3%.