The densities of solid thallium amalgams were measured pycnometrically at −79.0°C with the following results in g/ml: 13.946, 13.851, 13.465, 13.379, 13.219, 13.263, 13.267, 13.264, 13.184, 13.180, 13.177, 13.132, 13.063, 13.055 for the concentrations in weight % thallium of 8.72, 11.15, 19.45, susceptibilities of the amalgams were measured by the Gouy method over the same concentration range at temperatures from −180°C to 150°C. The alloys were diamagnetic and the susceptibilities were compatible with the phase diagram. The densities and the e.m.f. measurements on concentration cells show that the alpha phase at −79°C extends from 21.35 to 30.7 weight % thallium and at 0°C the alpha phase extends to 33.75 weight % thallium.