4. A thin lamina E, cut from a crystal of potassium bichromate, serving
to render the sodium light more monochromatic: When the saccharine
liquids under examination are colored the crystal of bichromate is
removed before the observation is made.
5. The polarizer R, which is rotatable through a small angle by the
lever K:
6. The lever JK for rotating the tube containing the polarizer: This is
operated by the rod X extending to the left.