A capillary technique was used to investigate the diffusion of 42K in melts of better than 99% purity (table 164). The data for 870 to 1017C could be described by:

D (cm2/s) = 2.46 x 10-3 exp[-7.5(kcal/mol)/RT]

Self-Diffusion of Na+ and K+ in their Molten Fluorides. K.Grjotheim, S.Zuca: Acta Chemica Scandinavica, 1968, 2[2], 531-7