The simultaneous presence of both PAX and cyanide species and their resulting impedance spectra in Fig. 12(b) and (d) suggest that both free cyanide and cuprous cyanide at the concentration studied completely inhibited the interaction between PAX and pyrite, but did not adsorb onto the mineral surface, since the capacitance went back to a similar value in background solution with the addition of cyanide species to PAX containing solution. It is apparent that in the presence of cyanide, the hydrophobic xanthate species are unstable and decompose from pyrite surface by forming much more stable cyanoferrous or cyanoferric complexes which might be soluble.