The demountable cells Type 49, with removable window, must be held together when being used. Cell holder Type CH-2049 is designed for this purpose. These cells may be taken apart for easy cleaning. This cell design is especially useful for opaque or viscose solutions. The cell consists of one fully fused component combining one window and the sides of the cell which forms the path length. The other window is separate and the cell can therefore be taken apart for cleaning. The cell wall and the removable window are polished so flat that the two will form a seal when placed in contact. Viscous and aqueous samples will allow the best seal to be formed, organic solvents will creep into the seal area for a less reliable seal.