Study of Soret effect and convection in an orginic solution

Placing a 1 mm thick chloroaluminum phthalocyanine-ethanol solution parallel and vertical to the optical table respectively, we measure the transmittance and deflection of a CW HeNe laser light normally incident on the sample. As a result, we observe monotonous increase of transmittance with time in the former geometry and lower transmittance first ascending and then descending with time in the latter geometry. According to additional path deflection measurements with a CCD camera, transmittance curves pertaining to both geometries are attributed to thermal diffusion alone and thermal diffusion followed by convection.