In the practice of ore dressing for depression of sphalerite flotation, ZnSO₄ or FeSO₄ in combinations with KCN, Na₂CO₃, Ca(OH)₂ in quantities ensuring the formation of a precipitate in the pulp, consisting of one or more compounds are used. P. A. Rebinder and coworkers, in a study of the contact angle of water on polished sections of sphalerite, did not detect a depressing effect of zinc sulfate on the surface of sphalerite, whether unactivated or pre-activated with copper ions. Currently, a number of authors believe that a possible cause of depression of sphalerite flotation is the adhesion of precipitates to the surface of mineral particles.