Abstract: An interfacial surface generating means having an inlet end, an outlet end and a plurality of separate passageways connecting the two ends. The ends of the passageways at the inlet end lie along a first line and the ends of the passageways at the outlet end lie along a second line. The second line extends substantially normal to the first line. Each of the ends being dish-shaped and having connecting means to fasten a plurality of surface generators together in a liquid-tight manner. The adjacent dish-shaped ends forming a mixing chamber between adjacent surface generators.