Method of making silicon nitride

In the manufacture of silicon nitride powder by the vapor phase reaction of a silicon halide with ammonia at an elevated temperature in a system where the silicon halide and ammonia are introduced into the entrance end of a reactor tube, pass through a hot zone thereof where they react with each other to form a reaction product, and where the reaction product passes out of the reaction tube at the exit end thereof and thence to collection means where the reaction product is collected in powder form, the improvement which comprises introducing moisture into the system at a point between the exit end of the reactor tube and the collection means while preventing the entry of room air into the system, both at the entrance end and exit end of the reactor tube, the moisture being introduced into the system under controlled conditions by flowing nitrogen through water and thence into the system.