for many ores (e.g. those of cu, mo, w, ni), the collectors are anionic sulfur ligands. particularly popular are xanthate salts, including potassium amyl xanthate (pax), potassium isobutyl xanthate (pibx), potassium ethyl xanthate (kex), sodium isobutyl xanthate (sibx), sodium isopropyl xanthate (sipx), sodium ethyl xanthate (sex). other collectors include related sulfur-based ligands: dithiophosphates, dithiocarbamates. still other classes of collectors include the thiourea thiocarbanilide. fatty acids have also been used.