Abstract: Apparatus for ejecting a mixture of liquids, e.g. urethane foam, comprises a cylindrical chamber into which the liquids are separately introduced under pressure and mixed and ejected from the open end of the chamber. A reciprocable plunger alternately exposes the inlets in its rear portion and seals the inlets from each other and purges the chamber in its forward position. The inlets are axially spaced apart and separated from each other by a throat that has interference fit with the plunger in the forward position of the plunger, the plunger having for this purpose an elastic deformable surface.