n-hydrocinnamoyl-n-phenylhydroxylamine (hcnpha) was found to float sphalerite without activation by copper sulphate. however, concomitant flotation of sulphidic gangue minerals, such as pyrite, significantly reduced the grade. adding 200 g/t of copper sulphate, which is approximately 80% reduction in the amount consumed in the xanthate reagent scheme currently used in the industry, improved the grade and the recovery.