Flame photometric determinations of diffusion coefficients. Part 2.—Results for sodium

Abstract

The diffusion coefficient for sodium atoms present in trace quantities in the burned gases of H₂+O₂+N₂ flames has been measured over the temperature range 1920-2520 K. The technique employed was the point source one adapted to atmospheric pressure flames. After various tests, the procedures used have been found capable of measuring diffusion coefficients accurate to within about 7 %. In addition, the velocity constants for thermal ionization of sodium atoms have been determined in the flames of highest temperature. The data on diffusion are found to be in accordance with predictions based on the Chapman-Enskog theory using a Lennard-Jones (12 : 6) potential function to describe interactions between flame species. The results indicate values of the Lennard-Jones force constants for sodium of σ= 2.11 × 10^–10 m and (ε/k)= 750 K.