The rate of evaporation of tantalum was determined by measuring the change of resistance and the change of weight of uniform filaments. Temperatures were held constant throughout each run by adjustments of voltage $V$ and current $A$ so that $V{A}^{\frac{1}{3}}$ remained approximately unchanged. The rate of evaporation can be expressed by ${log}_{10}M=7.86-\frac{39,310}{T}$, where $M$ is the rate of evaporation in grams per ${\mathrm{cm}}^2$ per sec. and $T$ is the temperature on the Kelvin scale.

• Received 2 March 1939

DOI:https://doi.org/10.1103/PhysRev.55.748