A flotation cell for separating hydrophobic particles from hydrophilic particles uses a mixer (1) with an air inlet (8) and slurry feed (7) to form a bubbly mixture in a u-tube mixer (4, 5, 6) and feed the mixture into a separation vessel (2). Plant cost and operating efficiencies are optimised by gravity feed of slurry and admitting air at atmospheric pressure. The separation vessel (2) has an upper inclined plate (9) which guides the froth layer (33) containing the hydrophobic particles to an overflow launder (11) without any significant turbulence or change in direction optimising the retention of hydrophobic particles in the froth, while the hydrophilic particles drop down in the liquid layer (34) guided along a lower inclined plate (24) to a tailings outlet (14).