Abstract: An injector for injecting gas into a molten metal. The injector has a rotor that is rotatable about an axis of rotation, the rotor having a cylindrical projection-free side surface, a bottom surface, and a cavity for receiving molten metal located centrally of the rotor with respect to the axis of rotation. The rotor is provided with a plurality of openings in the side surface spaced around the rotor for ejecting molten metal and gas from the rotor upon rotation of the rotor about the axis of rotation. At least one opening in the bottom surface communicates with the cavity permitting entry of molten metal into the cavity, and a plurality of passages disposed in the rotor interconnect the cavity and the openings in the side surface. A gas passageway introduces gas into molten metal present within the rotor but lacks direct communication with the cavity, and is provided with at least one outlet opening into at least one of the plurality of passages to ensure regular and even gas distribution.