A flow through pressure reaction apparatus that permits chemical reactions to take place between fluids maintained under pressure as the component fluids are moved from one location to another. The reaction is allowed to take place within an enclosed fluid conduit connected between the discharges of opposed pumps. At least one pump is a non-positive displacement pump that will allow reverse flow of fluid through it in response to increases in fluid pressure within the conduit. One pump receives fluid material and forces it through its discharge into the conduit. A second pump at the opposite end of the conduit receives the material at its discharge. The second pump is operated in opposition to the first pump at a pressure head that is lower than the pressure head of the first pump. A fluid flow will therefore be maintained through the second pump in a direction opposite to the flow it would normally produce because of the differential of the pressure heads of the two pumps.
