The diffusivity of oxygen in dilute alkaline solution from 0° to 65°C

Diffusion coefficients for oxygen in 0·1 M sodium hydroxide solution have been determined from 0° to 65°C using a rotating platinum electrode. The results may be represented with a standard deviation of approximately 1% by the expression:

where D_o = 8·03 × 10^?3cm²s^?1 and the apparent activation energy, Q_D, is 3·49 kcal mol^?1. Between 25° and 65°C the product of the diffusivity and the solution viscosity is essentially constant:

Values for diffusion coefficients for oxygen in pure water have been derived from these data with an absolute error probably less than 4%.Difficulties in obtaining reproducible results at a rotating platinum electrode are attributed to deactivation of the electrode by reduction of a surface oxygen phase. Results at the higher temperatures indicate that methods of determining diffusivities by diffusion through a stagnant layer of solution involve an increasing indeterminate error as the temperature rises, due to convective mass transport.