Abstract: A flotation apparatus has an array of flotation cells which are in serial fluid flow communication from a first to a last cell. Each cell is in overflow communication with an overflow froth receiving receptacle which preferably has a top lip of slightly varying height in each cell. Air inlet and mechanical agitation are provided for each cell and are so positioned to promote an upright circular fluid flow in each cell toward the froth receiving receptacle. Each cell has internal surfaces shaped and oriented to promote the upright circular fluid flow and to discourage the creation of reverse eddy currents within the cell.

Abstract: A process for recovering gold from a refractory sulfidic ore which has been suspended in an aqueous slurry and oxidized using nitric acid so that substantially all of the gold in the ore is made available for recovery and at least a portion of the sulfidic components present during the oxidation are oxidized to elemental sulfur, comprises bubbling air as a discontinuous phase upwardly through the oxidized slurry, thereby creating a froth containing elemental gold and sulfur. The froth is separated from the slurry to provide a concentrate, and the gold is recovered from the concentrate.

Abstract: A shut off seal in a device having a rotatable shaft extending through a nozzle side entry structure of a tank is provided by means of a slidable stuffing box housing which can be moved by jack screws into engagement with a sealing collar fastened to the shaft inboard of the housing. The arrangement enables the changing of the packing about the shaft without draining the tank.

Abstract: An oxidation process for releasing a metal of interest in an ore is described. The process is especially useful for releasing a metal of interest entrapped in a refractory ore. The process comprises reacting the ore with nitric acid until sufficient oxidation has occurred to release the metal of interest so that it may be recovered by conventional techniques. Nitric acid is regenerated in situ by aerating the liquid medium and contacting it with the off gases generated by the oxidation. The process is continuous and the nitric acid is recycled to the reactor preferably after removal of accumulated sulfate.

Abstract: A device for suspending solid particles in a turbulent fluid for the purpose of concentrating particles of interest such as mineral particles comprises an upright column provided with a plurality of impellers spaced along a rotatable shaft extending centrally within the column. An inlet is provided near the bottom of the column to introduce compressed gas which is dispersed by the rotating impellers to create a rising column of bubbles through a slurry of particles in a liquid so that a gas to liquid gradient is provided along the column. Disks are spaced along the shaft between the impellers, and baffles are provided longitudinally at the inner surface of the column to control the swirling of the fluid caused by the impellers.

Abstract: An oxidation process for releasing a metal of interest in an ore is described. The process is especially useful for releasing a metal of interest entrapped in a refractory ore. The process comprises reacting the ore with nitric acid until sufficient oxidation has occurred to release the metal of interest so that it may be recovered by conventional techniques. Nitric acid is regenerated in situ by aerating the liquid medium and contacting it with the off gases generated by the oxidation. The process is continuous and the nitric acid is recycled to the reactor preferably after removal of accumulated sulfate and dissolved metal cations.