The interactions of As(III) ion with C2H5OCS2- and C2H5SCS2-, known as the most popular collector ions, were studied by density functional theory (DFT) at the B3LYP/6-31G** level in connection with the arsenic-containing minerals realgar, orpiment, and arsenopyrite. The dixanthogen formations of these ions were also investigated at the same level of theory. The central purpose of this paper is to compare the stabilities of the major flotation products, namely As(III) xanthates and dixanthogens. The results show that the magnitudes of the interaction energies for the formations of As(III) xanthates and dixanthogens increase when the oxygen atom is replaced by the sulfur atom in C2H5OCS2-. Therefore, the C2H5OCS2- ion is preferred in these formations. The results obtained are in agreement with the experimental data reported. (c) 2004 Elsevier Inc. All rights reserved.