Electric Resistance and Thermo-electric Power of Germanium, from — 191° to 675° $R=log A+aT+\frac{Q}{\mathrm{kT}}$.—Measurements were made on a pure specimen of this rare metal in the form of a rod 2.4 by 0.44 by 0.41 cm., prepared under the direction of L. M. Dennis. The current was led in through graphite blocks and thermo-junctions were placed in grooves near each end. For the thermo-electric power determinations a temperature gradient was secured by placing the specimen in a non-uniform part of a furnace or refrigerator and also by using a heater coil wound on one end. Between 125° and 450° the results indicate a slow reversible transformation of some sort, for below and above this range the thermo-electric power is a linear function of the temperature and also, except in the range 100° to 600°, the resistance is an exponential function of the form $log R=log A+aT+\frac{Q}{\mathrm{kT}}$. The specific resistance reaches a minimum at - 116° and again at 645°, the temperature coefficient changing from positive to negative with rising temperature. Its value at 0° is 0.089 ohm per cm. cube.

Periodic Relations among the Elements with Reference to Temperature Variation of Resistance are pointed out. High resistance elements toward the right side of the Periodic Table have characteristically negative coefficients while the good conductors toward the left side have positive coefficients. The elements in Group IV, C, Si, Ti, Ge and Zr show transitional behavior, each giving indications at least of a minimum resistance at temperatures which decrease regularly from very high for the lightest to very low for the heaviest element.

Transformation in Germanium, 125° to 450° $C$., as indicated by the above data, shows no hysteresis, the rapid cooling curves duplicating the slow cooling and heating ones. The phases are always in equilibrium, one, perhaps, being dissolved in the other.

• Received 1 December 1921

DOI:https://doi.org/10.1103/PhysRev.19.447