The objective of this work is to study the Diffusion-thermo effect (Dufour effect) on unsteady MHD free convective heat and mass transfer flow of a viscous incompressible electrically conducting, radiating and chemically reacting fluid past a semi-infinite vertical permeable plate embedded in high porous medium with time dependent suction. A uniform magnetic field of strength Β is applied in the transverse direction to the fluid flow. The dimensionless governing equations are solved by a regular perturbation technique. The effect of flow parameters on velocity, temperature, concentration, the rate of heat transfer, the rate of mass transfer and the skin friction coefficients are shown in graphical and tabular forms.Β It is observed that the effect of Dufour number on temperature and velocity field is significant near the plate. Keywords: chemical reaction, MHD, porous medium, radiation and Dufour number
