Black medicine No. 3501 is a kind of high-grade black medicine. It has stronger harvesting ability than butyl ammonium and sodium butyl sulphate. It has strong trapping ability for copper, silver, zinc and molybdenum sulfide ore. It is selective for iron sulfide ore. The medium mine also has a strong harvesting capacity, which is fast and can be added to the graded overflow or roughing operation, and must be added in stages. With strong foaming, the amount of addition must be controlled to adjust the foaming conditions.