Modem IR instruments such as interferometers used with diffuse reflectance accessories or "in situ" ATR experiments allow the characterization of the state of sulphide mineral surfaces and specially galena after wet or dry grinding and collection with xanthates. After dry grinding only lead xanthate, either monocoordinated or in the three dimensional form, is formed depending on the initial xanthate concentration. Wet grinding leads to heterogeneous adsorbed layer formed with monocoordinated lead xanthate and dixanthogen at low concentrations (monolayer domain), stoichiometric or non-stoichiometric lead xanthate, dixanthogen, and the dimer of the monothiocarbonate for higher concentrations.