Thermodynamic data in the «-phase of thehydrogen-palladium system offer particularly relevant quantitative tests of statistical models for hydrogen absorption by palladium, 1-6 since complications, such as hystere-sis, arising from the formation of the high content ßphase are absent and yet the postulated HH interac-tion which leads to the/3-phase formation must still be present. Below~ 120 equilibrium isotherm data utilizing conventional gas phase absorption techniques have been difficult to obtain because of slow equilibration. The early gas phase absorption isotherms (0, 30, and 80) of Gillespie and Hall1 23456 were the only available «-phase data at low temperatures until the recent, and quite different, resultsbetween 0 and 75 obtained by Wicke and Nernst, 7 8using a novel gas phase technique in which a catalyst, more active for H2 dissocia-tion than a palladium surface, was placed in intimate contact with a palladium sample, thus allowing a rela-tively rapid attainment of equilibrium. In view of the difficulties encountered with conven-tional gas phase techniques at lower temperatures (< 120), thepresent study of the «-phase, which was undertaken prior to the publication of Wicke and Nernst’s results, utilized the technique of absorption from dilute HC1 solutions. The technique of direct absorption from hydrogen-stirred dilute HC1 solutions has been shown to be a valid method of obtaining ther-modynamic data in the two-phase region of the hy-drogen-palladium system. 8-11 While it has been known for some time that theelectrode potentials and resistiv-