Microflotation showed nickel (II) oxide responded to amyl xanthate over a pH range 4 to 8. Zeta potential measurements confirmed the presence of xanthate on the surface by an acid shift in isoclectric point. Solid-state absorption infrared spectroscopy (KBr pellet technique) suggested chemisorption in which a terminal anionic sulphur of amyl xanthate bonds to nickel in a monodentate fashion. The solid state IR technique required excess xanthate over that used by flotation. Headspace analysis gas-phase infrared spectroscopy (HAGIS) permitted analysis at the concentration used in flotation and supported the interpretation of the surface species. (C) 2002 Elsevier Science B.V. All rights reserved.