Flame photometric determinations of diffusion coefficients. Part 5.—Results for calcium hydroxide, strontium hydroxide, barium hydroxide and copper

Abstract

Diffusion coefficients are measured for trace quantities of the additives Ca, Sr, Ba and Cu in the burnt gases of flames of H₂, O₂ and N₂ over the temperature range 1900–2520 K. The alkaline earth metals exist in these flames chiefly as the dihydroxides, whereas with copper the dominant species is free atoms. The measured diffusion coefficients are interpreted in terms of two intermolecular potential functions to describe interactions between the diffusing and flame species, which are H₂, H₂O and N₂. It is concluded that the Lennard-Jones function is preferable here to a purely repulsive inverse power one. Values of the Lennard-Jones parameters are presented together with the constants characterising purely repulsive forces. In addition, two mixing rules are investigated for describing the overall diffusivity of a tracer in a multicomponent mixture in terms of a set of binary diffusion coefficients.