Abstract: An apparatus for mixing a plurality of vessels containing various sample and reagent materials is disclosed. The apparatus comprises mechanisms for holding the vessels and rotating the vessels about an axis. A valve for venting pressure is provided and is controlled by a solenoid that is actuated only when the vessels are in a generally upright position so that liquid or solid contents of the vessels will not escape through the pressure venting valve. Additionally a work station is provided that houses the apparatus of the present invention and allows the user to complete the mixing and extracting process without removing the vessels from the holding tray.