A volume-control receptacle has a reservoir with a bottom. The reservoir is adapted for receiving a fluid. The receptacle has a plurality of capillaries opening on the reservoir at a specific height above the bottom; the capillaries draw off the excess fluid from the receptacle, thereby leaving a specific amount of fluid in the reservoir. In a preferred embodiment, the volume-control receptacle is adapted for use with a disposable cuvette. The reservoir of the receptacle has a drain at the bottom connected to the cuvette for delivering the fluid to a testing instrument or other final application point. The volume-control receptacle has a lip projecting upward from a promontory of the receptacle. A rib extends downward from the lip to the bottom of the reservoir for guiding the fluid into the reservoir.