Measurement of Sodium-Vapor Density at Very Low Pressures by an Optical Method*

Abstract

The density of sodium-saturated vapor has been measured in the range 100°C–180°C. The density values were obtained by measuring the absorption coefficient of the D_I line by magnetic scanning. The absorption line was scanned by placing a spectral lamp in a variable magnetic field and by filtering out one of the components of the emitted D₁ line. The experimental points have been fitted with the equation logp = A − B/T + C logT. Together with our measurements we considered as well all of the other available data below 300°C. The best values of A, B, and C were found to be A = −55.182 40; B = 1081.2523; C = 20.029 33.