Summary:1.The velocity and selectivity of mineral flotation from ores depends markedly on the formation of the optimum volume of flocculated-structure foam in the cell.2.When flocculated foams are formed in basic flotation without further purification operations, it is possible to obtain apatite concentrates with 39.4% P2O5 at 85–88% extraction; coarsely crushed ores largely promote the formation of these concentrates.3.The hydrodynamic conditions in the cell govern the formation of flocculated foams with highly dispersed air bubbles; increase of hydraulic resistance in the slurry leads to the formation of concentrates with large P2O5 contents, but at lower velocity; as the solids content of the slurry increases, the relative flotation velocity at first increases, then, in dense slurries, decreases.