The Thermal Expansion of Bismuth Crystals

IN order to provide data which shall form a basis for a theory of non-cubic metallic crystals, Gruneisen and Goens have carried out experiments on the thermal expansion from 180° C. to 100° C. and on other properties of single crystals of zinc and cadmium, the results of which were published in the Physikalische Zeitschrift for December 15, 1923. They mention that crystals of bismuth and antimony have not yet been studied. For some time I have been engaged on an investigation of the thermal expansion of bismuth crystals from ordinary temperatures up to the melting-point 269° C. The experiments above 220° C. are not yet quite complete, but the results obtained up to this temperature indicate that the behaviour of bismuth crystals is different from that of the metals examined by Gruneisen and Goens. In the case of bismuth the expansion in either direction, i.e. parallel or perpendicular to the axis, is practically uniform over this wide range. The results of Gruneisen and Goens show a considerable variation in both expansion coefficients in the range 0° to 70° C. for cadmium crystals, and in the expansion coefficient perpendicular to the axis for zinc crystals. It is hoped that full details of these experiments will be published shortly.