A feedstock injector for connection to a source of heated gas comprises a converging channel extending from the upstream end to the downstream end of the injector. A splitting arm extends diagonally within the converging channel, the splitting arm comprising two symmetrically opposed surfaces extending from the inlet to the outlet ends of the converging channel. A feedstock injection passage opens axially at the downstream end of the splitting arm. The gas stream discharged by the injector contacts and entrains the feedstock with improved uniformity.