Some Thermal and Electrical Properties of Beryllium

Abstract

Specific heat.---The specific heat of beryllium was obtained from cooling data by equating the heat loss per cm length per unit time from beryllium to that from zinc. The values obtained increase rapidly with a rise in temperature from 0.0389 at -175.6\ifmmode^\circ\else\textdegree\fi{}C to 0.593 at 190\ifmmode^\circ\else\textdegree\fi{}C.Thermal conductivity.---The modified Forbes method of Bidwell was used to determine the thermal conductivity of this metal. Values of $k$ were calculated with three different sets of distances from the first junction as origin for each run at a given surrounding temperature. $k$ was found to increase with a rise in temperature from 0.232 at -176.2\ifmmode^\circ\else\textdegree\fi{}C to 0.508 at 190.4\ifmmode^\circ\else\textdegree\fi{}C.Specific resistance.---The specific resistance varies according to the heat treatment given the sample. Values recorded in this article are those obtained after a steady condition had been established after repeated treatments from liquid air temperature to 700\ifmmode^\circ\else\textdegree\fi{}C. Measurements made on two samples check each other closely. They are: 1.56 microhms at -191\ifmmode^\circ\else\textdegree\fi{}C; 6.76 microhms at 22\ifmmode^\circ\else\textdegree\fi{}C; 19.05 microhms at 305\ifmmode^\circ\else\textdegree\fi{}C; and 40.00 microhms at 690\ifmmode^\circ\else\textdegree\fi{}C.Temperature coefficient of resistance.---The temperature coefficient of resistance, \ensuremath{\alpha}, is not a constant over the above range. It increases with a rise of temperature but not linearly. The graph of this quantity plotted against temperature shows three distinct sections, $\ensuremath{\alpha}$ has the following values: 0.000371 at -190\ifmmode^\circ\else\textdegree\fi{}C; 0.00667 at 20\ifmmode^\circ\else\textdegree\fi{}C; 0.00800 at 310\ifmmode^\circ\else\textdegree\fi{}C; 0.00858 at 500\ifmmode^\circ\else\textdegree\fi{}C; and 0.01196 at 685\ifmmode^\circ\else\textdegree\fi{}C.Thermoelectric power.---The thermoelectric power of beryllium against lead seems to vary linearly with temperature. However, at -50\ifmmode^\circ\else\textdegree\fi{}C the graph of the thermoelectric power plotted against temperature shows a break. This, considered in connection with the results obtained for the temperature coefficient of resistance, suggests the probability of a change in allotropic form.Wiedemann-Frantz-Lorentz law.---The Wiedemann-Frantz-Lorentz law, that $\frac{k}{\ensuremath{\sigma}T}$ is a constant, is not obeyed by this metal.