Abstract: The invention relates to a method and an apparatus for the separation of hydrophobic substances by froth flotation that basically consists of feeding pulp in the form of a thin layer on at least a lower gas-permeable slanted surfaces in which low pressure gas is injected generating small bubbles that collect hydrophobic particles. The froth containing concentrate is separated and washed before removal in a froth reservoir formed by a lower gas-permeable slanted surface and a wall at its lower end. At the top of the wall, the froth overflows to a launder for removal. At the bottom of the wall, the pulp containing the tailings discharges through an opening. Froth washing is performed by means of baffles that force the froth to flow underneath water sprays.