Interaction of as-prepared single-walled carbon nanotubes (SWNTs), containing a mixture of metallic and semiconducting species with the potassium salt of coronene tetracarboxylic acid, I, in an aqueous medium provides a simple method of separating semiconducting and metallic species. The metallic nanotubes precipitate out on interaction with I while the semiconducting nanotubes remain in solution. The method avoids centrifugation and is amenable for large-scale separation and can be used as a routine laboratory procedure. Interestingly, interaction with strong electron acceptor molecules brings about metal-semiconductor transitions in SWNTs