the amount of highly-liberated particles recovered decreased with the increase of flotation time. A greater amount of this liberation class was recovered when the flotation pulp was conditioned in the presence of SIBX. For example, when flotation pulp was treated with 25 g/t of SIBX, the Con-2 had 10% more highly liberated particles than in the absence of SIBX. The increase of SIBX dosage also improved recovery of particles having less than 25% of copper sulphide, particularly in the later concentrates.