The objective of this paper is to analyze the onset of Marangoni convection for absorption process accompanied by heat transfer using propagation theory. Ammonia-water is used as a representative solution pair for the absorption process and 2-ethyl-1-hexonal is considered an additive. The re-modified solutal Marangoni number MBs is linearly related to the modified solutal Biot number Bs*. Rearranging this relation, a useful correlation of the solutal Marangoni number Ms with respect to the solutal Biot number Bs is obtained in a linear form. It is found that there is a critical Bs causing the most unstable state of fluid layer. The critical time tau(c) to mark the onset of Marangoni convection can be predicted using the correlation developed in the present study. The results from the present study will provide a guideline to enhance heat and mass transfer performance during the absorption process. (C) 2003 Elsevier Ltd. All rights reserved.