Electrical Resistance and Thermo-Electric Power of the Alkali Metals

Electrical resistance and thermo-electric power of the five alkali metals, -183°C to 250°C.—Pure samples of the metals were fused into glass or quartz tubes, and measurements were made by means of thermo-junctions sealed into each end. Enough points were secured in each case to determine the slopes and the breaks in the curves. In both the resistance and thermo-electric power lines, changes of slope are observed beginning gradually 100 degrees or more below the melting point. These are taken to indicate transformations in each case from an $\alpha$ to a $\beta$ form. These transformations occur at approximately the temperatures, 50°C for Li, -20°C to +20°C for Na, -120°C for K, -35°C for Rb, and -80°C for Cs. In all cases a sharp rise in thermo-electric power and resistance occurs as the melting point is approached. The temperature coefficients of resistance decrease smoothly with increasing atomic weight for all forms.