A rack for holding containers containing liquids used in clinical chemistry analyzers. The rack comprises (a) a frame having two or more sections, each section being adapted for receiving a liquid containing component, at least one of the sections of the frame being adapted for receiving a first liquid containing component which is adapted for being removably but tightly mechanically connected to said frame, (b) at least one movable part adapted to be removably coupled to a shaker device, the movable part being adapted for receiving and holding a second liquid containing component, at least one of the sections of the frame being adapted for receiving the movable part and allowing motion of the movable part within predetermined limits.