Abstract: A process is disclosed for the mixing of relatively small amounts of liquid or liquefied additive with relatively large amounts of solid granular material comprising: forming, in a conduit, a continuous pneumatic- or gravity-borne stream of solid granular material; passing an inert gas stream through a constricting orifice to maintain sonic velocity flow conditions therein; concurrently introducing a stream of said liquid or liquefied additive into said inert gas stream in said constricting orifice under conditions such that combined stream sonic velocity flow conditions are maintained; and introducing the resulting combined liquid or liquefied additive and inert gas streams into said conduit to effect addition of said liquid or liquefied additive to said solid granular material.