Convection and thermal diffusion in a solution heated from below II. The system CHBr2 center dot CHBr2-CHCl2 center dot CHCl2

The critical point for the onset of convection (Benard point) was determined for the system CHBr2 center dot CHBr2 - CHCl2 center dot CHCl2. No stabilizing effect was observed. Experiments which sampled this and a conventional thermal diffusion cell (cf. following letter) to directly measure the concentration gradient due to thermal diffusion revealed that the gradient was destroyed when the solution is heated from below. This is an unexpected and important observation.