Thermodynamic Properties of Liquid Helium Three. I. The Specific Heat and Entropy

Abstract

Specific heats of saturated liquid ${\mathrm{He}}^{3}$ have been measured between 0.37\ifmmode^\circ\else\textdegree\fi{} and 2.36\ifmmode^\circ\else\textdegree\fi{}K. The data fit the empirical equation, $C=0.577+0.388T+0.0613{T}^{3}$ (cal/mole deg), to about \ifmmode\pm\else\textpm\fi{}1.0 percent between 0.5\ifmmode^\circ\else\textdegree\fi{} and 1.7\ifmmode^\circ\else\textdegree\fi{}K. The standard deviations of most of the individual points are between 1 and 2 percent.Entropy differences are calculated from the above equation and combined with a value of entropy of 1.44 cal ${\mathrm{mole}}^{\ensuremath{-}1}$ ${\mathrm{deg}}^{\ensuremath{-}1}$ at 0.5\ifmmode^\circ\else\textdegree\fi{}K to give the total entropies.The difference between the total entropy and the entropy of nuclear spin disorder is remarkably linear with and nearly proportional to $T$.The present and earlier warmup experiments give no indication of existence of a specific heat anomaly in liquid ${\mathrm{He}}^{3}$ between 3.21\ifmmode^\circ\else\textdegree\fi{}K and 0.37\ifmmode^\circ\else\textdegree\fi{}K. The present work also shows that a $\ensuremath{\lambda}$ transition comparable to that occurring in liquid ${\mathrm{He}}^{4}$ will not be found in liquid ${\mathrm{He}}^{3}$ at any temperature below 0.37\ifmmode^\circ\else\textdegree\fi{}K.