The present invention relates to a processing solution supply cartridge which utilizes a single container for a single-part developer concentrate. The single container has at least two valves or necks and is adapted to be utilized on a existing processor or processing machine. The single developer container design of the present invention assures a complete emptying of the container by permitting the simultaneous replenishment of single-part developer through each of the valves into the processing machine. With the combination of the single developer container and the single-part developer the process of metering distinct developers through distinct containers is not required. By facilitating the complete emptying of the developer container, the likelihood of developer solution remaining in the container is minimized.