The present invention relates to a processing solution supply cartridge that utilizes a single developer solution holding area having interconnected compartments for a single-part developer concentrate. The holding area has interconnected compartments and includes valves that permit the cartridge to be utilized on an existing processor or processing machine. The design of the present invention assures a complete emptying of the cartridge by permitting the simultaneous replenishment of single-part developer through the valves into the processing machine.