Effect of sodium bicarbonate and sodium arsenite on the facilitated transport of carbon dioxide through alkaline liquid membrane was investigated in view of the ionic strength and the pH of the solution through the boundary layer approximation. With the increase in the content of sodium bicarbonate, the pH of the solution increased while the difference of pH across the membrane decreased. Under the same ionic strength of the solution the concentration gradient of bicarbonate ion in the membrane increased and the pH and its gradient decreased with the content of sodium arsenite. It was confirmed that sodium arsenite facilitated the transport of carbon dioxide not only by catalyzing the hydrolysis of carbondioxide but also by buffering the pH.