A valve apparatus (2) for selectively distributing the sequential passage of separate, organic fluids to a common receiver, such as a reaction vessel. The valve apparatus comprises a valve body member (16) having multiple openings (56) and a plurality of separate conduits (54) each communicating a fluid source with one of the openings. The body member also has a common passage (60) with circular groove portions (62) surrounding the openings so that fluid flows radially outward from the openings toward the common passage. A plurality of pistons (30) are individually reciprocable between first and second positions for controlling fluid flow between associated openings and the common passage. The invention also provides a system (100) and method for measuring and delivering a precise quantity of each of the organic fluids, e.g., chemical reagents, to the reaction vessel.