Simultaneous heat and mass transfer in buoyancy-induced laminar boundary-layer flow along a vertical plate is studied for any ratio of the solutal buoyancy force to the thermal buoyancy force by using a new similarity transformation. The effects of the buoyancy ratio and Lewis number on the rates of heat and mass transfer are presented explicitly for most practical gaseous solutions (Pr=0.7, 0.21 less than or equal to Sc less than or equal to 2.1) and aqueous Sc solutions (Pr=7, 140 less than or equal to Sc less than or equal to 1400). Very accurate correlations of Sh the mass transfer and heat transfer rates are developed for the cases of single and combined buoyancy forces.
