Abstract
The velocity of thermophoresis of aerosol particles in the slip flow region, about which no conclusion has yet been drawn from the many results of experimental and theoretical work, was studied from the experimental point of view. A new experimental method using an ultramicroscope was developed to meet most of the necessary conditions to obtain reliable data on thermophoresis, such as accurate observation of velocity under an accurately known temperature gradient and prevention of the action of any forces except thermal force. The experimental results were compared with some of the most representative theories, and were found in good agreement with Derjaguin''s theory.
