β-Uranium Hydride: Heat Capacities from 1.4 to 23 °K and Some Derived Properties

The heat capacity of the metallic, ferromagnetic compound $\beta -\mathrm{U}{\mathrm{H}}_3$ was determined from 1.4 to 23 °K. An attempt was made to fit the data at the lowest temperatures by an equation of the form $C_p=\gamma T+A{T}^3+B{T}^{\frac{3}{2}}$, where $\gamma T$ is the contribution of the conduction electrons, $A{T}^3$ is the lattice contribution, and $B{T}^{\frac{3}{2}}$ is the magnetic contribution. The coefficient $\gamma$ is 29±1 mJ °${\mathrm{K}}^{-2\mathrm{}}$ ${\mathrm{mole}}^{-1\mathrm{}}$. Because of uncertainty in the magnetic contribution, no reliable estimate of $A$ or of the Debye $\Theta$ could be made. The thermodynamic functions $S^{\circ }$, $\frac{(H^{\circ }-H_0^{}{}_{}{}^{\circ })}{T}$ and $\frac{(G^{\circ }-H_0^{}{}_{}{}^{\circ })}{T}$ were reevaluated as 63.67±0.13, 30.24±0.06, and -33.43±0.07 J ${\left(\mathrm{°}\mathrm{K}\mathrm{m}\mathrm{o}\mathrm{l}\mathrm{e}\right)}^{-1\mathrm{}}$, respectively, at 298.15 °K.