Humboldt State University ® Department of Chemistry
Robert A. Paselk Scientific Instrument Museum
Precision Polarimeter, Rudolph 80
Humboldt State College; 1960
This instrument uses a Nicol prism to produce a beam of plane-polarized light (generally the sodium D line is used as the monochromatic source), which then passes through a sample tube, after which it is analyzed using a second Nicol prism with a circular scale. In order to improve the readability and accuracy of the instrument another Nicol prism, called a Lippich prism, is placed in front of the polarizer to create a split field by introducing a few degree rotation for half of the light. The instrument is now adjusted to match the two halves of the resulting field. The polarimeter can be used to determine concentrations of optically active substances as well as to aid in the identification of unknown compounds.
Some contemporary/early descriptions of the polarimeter and its use are provided below: