Abstract: The interaction of drops floating on liquid surfaces is important for many natural processes and industrial applications. In many cases, the system is multicomponent, leading to Marangoni flows on the surface, which might lead to repulsive forces between the drops. Here we investigate the combined effect of the attractive ``Cheerios effect'' and the repulsive solutal Marangoni flow by observing the behaviors of two identical oil drops floating on a partially miscible pool made of ethanol-water mixtures. Three typical behaviors are found: Repel, Attract-Coalesce and Attract-Rebound, in which the drops repel each other, attract each other and then coalesce, and attract and rebound upon contact. A scaling theory based on the two competing forces is developed to distinguish the repulsive and attractive behaviors of the drops. For the transition from Attract-Coalesce to Attract-Rebound, a lubrication layer is found to form when the immersed lower halves of the drops are more than half a sphere, which prevents the drops from coalescing. Our work may improve the knowledge on drop manipulations on liquid surfaces.

Key words: floating drops, Cheerios effect, Marangoni flows