Convection in a partially divided square enclosure with combined horizontal temperature and concentration: gradients was studied experimentally. An electrochemical system was employed to impose the concentration gradients. The concentration and temperature differences were achieved by heating the cathode and cooling the anode. The partition plate was adiabatic and was oriented parallel to the isothermal sidewalls. Thermal Grashof numbers ranging from 6.94 x 10(5) to 1.1 x 10(6) solutal Grashof numbers from 7.02 x 10(6) to 1.62 x 10(7), and partition ratios of 0.125 and 0.25 were investigated. Because of the large difference between the thermal and solutal diffusion rates, the pow had double-diffusive characteristics. Various flow patterns were observed under different experimental conditions. It was demonstrated that the partition ratio has strong effects on both the mass transfer rate and the flow pattern.