1. It has been confirmed that the flotation of sulfur black suspensions is dependent on the electrokinetic poten tial of the dye, as measured by the migration velocity.2. Several new floating agents have been found to be effective alone and in mixtures.3. Partial coagulation of the dye with electrolytes or positive colloids before addition of floating agents has proved to be effective. The improvement is directly con nected with the change in the electrokinetic potential of the dye caused by the coagulating agent.