Abstract: Enhanced macromixing, mesomixing, and micromixing of multiple discrete reactant streams, particularly for precipitation reactions of low density pumpable fluids, are obtained by controlled continuous high pressure multiple reactant streams flowing into a chemical mixer/reactor. Individual reactant streams are pressurized to about 8,000 to 50,000 psi and achieve velocities up to about 250 meters/second in the final stage of the chemical mixer/reactor. Reactant flows are controlled by a combination of a fixed restriction and a variable driving pump.