An apparatus for preparation of a chemical solution, comprising: a lower housing having a base , an upper plate , and a side wall , the side wall extending upwardly from the base to the upper plate, the upper plate having a central opening therein so that the upper plate has an annular shape; an upper housing having a side wall , a lower extremity of said side wall connected to the upper plate; a grid mounted on the upper plate and covering the central opening, the grid forming at least a portion of a lower boundary of an upper chamber within the upper housing; a wall in the interior of the lower housing, said interior wall connected to the base and extending into an upper portion of the lower housing, said interior wall thereby dividing the interior of the lower housing into a central inner chamber and an annular outer chamber , at least a portion of said interior wall having a reduced height to permit fluid flow from the inner chamber to the outer chamber; a nozzle disposed in the inner chamber for discharging fluid into the inner chamber toward the grid, so as to cause a fluid surface in the inner chamber to be locally elevated in a portion of said surface; and an outlet port in the side wall of the lower housing for conducting the chemical solution out of the outer chamber; wherein the inner chamber is substantially cylindrical and said nozzle is disposed vertically in a central portion of the inner chamber, so that said locally elevated portion of said surface is above a central portion of the grid; characterised by said nozzle comprising an eductor oriented so as to discharge fluid vertically upward toward the grid; and the eductor having fluid intake ports effective to create a Venturi effect and thereby draw fluid in the inner chamber into the eductor. a lower housing having a base , an upper plate , and a side wall , the side wall extending upwardly from the base to the upper plate, the upper plate having a central opening therein so that the upper plate has an annular shape; an upper housing having a side wall , a lower extremity of said side wall connected to the upper plate; a grid mounted on the upper plate and covering the central opening, the grid forming at least a portion of a lower boundary of an upper chamber within the upper housing; a wall in the interior of the lower housing, said interior wall connected to the base and extending into an upper portion of the lower housing, said interior wall thereby dividing the interior of the lower housing into a central inner chamber and an annular outer chamber , at least a portion of said interior wall having a reduced height to permit fluid flow from the inner chamber to the outer chamber; a nozzle disposed in the inner chamber for discharging fluid into the inner chamber toward the grid, so as to cause a fluid surface in the inner chamber to be locally elevated in a portion of said surface; and an outlet port in the side wall of the lower housing for conducting the chemical solution out of the outer chamber; wherein the inner chamber is substantially cylindrical and said nozzle is disposed vertically in a central portion of the inner chamber, so that said locally elevated portion of said surface is above a central portion of the grid; characterised by said nozzle comprising an eductor oriented so as to discharge fluid vertically upward toward the grid; and the eductor having fluid intake ports effective to create a Venturi effect and thereby draw fluid in the inner chamber into the eductor. <EOS>