Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Precision Polarimeter, Rudolph 80


Humboldt State College; 1960

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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.

The polarimeter was first used as a chemical instrument by Jean Baptiste Biot around 1816.1 By the mid nineteenth century they had achieved essentially modern form and they remained essentially unchanged through the 1980's. This instrument was in use by the HSU Chemistry department from 1960 until the 1980's. Dr. Mervin Hanson, a chemistry major at HSU from 1956 to 1961 and later a professor in the chemistry department, recalls using this instrument to follow the kinetics of mutatrotation. He recalled the polarimeter being purchased at least in part so students would be able to use a research grade instrument.

Some contemporary/early descriptions of the polarimeter and its use are provided below:


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This Polarimeter is described as item R3122, Rudolph High Precision Polarimeter, Model 80 on pg 775 of the Schaar Scientific Company catalog, Selected Laboratory Equipment and Chemicals 63/64 (1963).

1 Turner, Gerard L'E. Nineteenth Century Scientific Instruments. Sotheby/U Cal., London/Berkeley (1983) p 222.

From the Analytical/Physical Chemistry Lab - Exhibit Catalog

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HSTC (1921-34)
HSC 54-73 icon
HSC (1954-1973)
HSC 35-53 icon
HSC (1935-1953)

HSC 1956-72 Instrument Collection

© R. Paselk
Last modified 16 August 2010