Adsorption of Mixtures ofHe3andHe4

The distribution of ${\mathrm{He}}^3$ between the vapor phase and dilute mixtures of ${\mathrm{He}}^3$ in ${\mathrm{He}}^4$ adsorbed on jewellers' rouge (${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$) has been measured between 1.6°K and 2.3°K, for saturations in the range 15 percent to 99 percent, corresponding to film thicknesses of 1.3 to 34 layers. The ratio of the mole fraction of ${\mathrm{He}}^3$ in the vapor phase to that in the adsorbed phase is practically independent of the thickness of the asdorbed film, and essentially the same as for the bulk liquid case. The onset of superfluidity in the adsorbed films does not influence the ${\mathrm{He}}^3$ concentration in samples taken by simple desorption techniques.