Diffusion of thallous ions in potassium bromide, measured by the spectrophotometric method

The diffusion of thallous ions in potassium bromide, in the impurity range of temperatures, was measured by the spectrophotometric method.¹ The energy of activation Q was found to be 23,500 cal/mole. The pre-exponential factor D₀ varied with the experimental conditions, the effect being attributed to variations in the "face boundary", as indicated by experiments carried out under a reduced atmospheric pressure. From experiments with pressed pellets it was deduced that the original equation (containing the factor 6² to account for the "face boundary") used in calculating the diffusion constants D needed correcting as follows: D = (E_t/E_∞)²tl²/(10.3)²t. This gives for the diffusion of thallous ions in potassium bromide: D_Tl+ = 0.23 exp (-23,500/RT)cm²/sec. Previous values of D and D₀ reported for the diffusion of thallous and lead ions in potassium chloride should similarly be divided by a factor of three.