With the quantitative Schlieren system, Marangoni convection in the process of the physical desorption of acetone from water is observed and analyzed. An unstable desorption process is selected to investigate the flow patterns of the Marangoni convection and its driven mechanism. Based on the shadow Schlieren images, the flow patterns of Marangoni convection are analyzed and the concentration gradients in the vicinity of interface are obtained. The experimental results show that chaotic flow patterns happen frequently and they are different from regular Marangoni flow such as roll and cellular. The further researches indicate that it is the main reason to induce the Marangoni convection that the local sharp concentration gradients along the interface of the gas and liquid. (c) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved.