Adsorption of Mixtures of He3 and He4

The distribution of He³ between the vapor phase and dilute mixtures of He³ in He⁴ adsorbed on jewellers' rouge (Fe₂O₃) 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 He³ 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 He³ concentration in samples taken by simple desorption techniques.