Closed cell for use in spectrophotometers

A closed cell adapted to receive a liquid to be subjected to analysis and an air space or bubble to absorb pressure differentials, the cell including means to retain the air space or bubble in a predetermined location in the cell, the said means comprising a restriction element formed in a passage connecting the first chamber and the second chamber and adapted to facilitate the air space or bubble passing from the first to the second chamber and to inhibit the air space or bubble passing from the second chamber to the first chamber, the restriction element being formed by a transverse wall that extends partially across the chamber to define a passage between a wall of the first chamber and the free end of the transverse wall and wherein, the free end of the transverse wall is profiled such that the area of the passage decreases in a direction from the first to the second chamber.