Density Changes in SolidH2

Abstract

The relative difference in molar volume between solid ortho- and para-${\mathrm{H}}_2$ is found to by $\frac{(V_p-V_o)}{\overline{V}}=(1.3\mathrm{}\pm 0.2)\%$ at 4.2°K. We also report the change in molar volume for a given ortho concentration as a function of temperature, in particular, upon the transition from hcp to fcc.