Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Humboldt College; c.1950
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 aother 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 1953 until 1986.
Winkel was founded in 1857 by Rudolf Winkel and soon began making student microscopes. In 1911 the name was changed to Winkel-Zeiss when Zeiss acquired an interest in the company. Polarizing microscope stands were a specialty. Around 1935 the name was changed to Zeiss-Winkel. Winkel-Werke was still in production after WW2, and remains the principle place of manufacture of West German Zeiss microscope stands.2
The instrument is supported by two tapered iron pillars, to give an overall height of 16" on an oval cast iron base (6 1/2 x 13 1/2"), all in black crinkled finish. The 4.75" readout circle is graduated in degrees, with a vernier readout to 0.1° observed through a magnifier, and illuminated via a small adjustable mirror. Original decal (now removed): State of California/43919.
1 Turner, Gerard L'E. Nineteenth Century Scientific Instruments. Sotheby/U Cal., London/Berkeley (1983) p 222.
2 Bracegirdle, Brian. Notes on Modern Microscope Manufacturers , Quekett Microscopical Club (1996) p 82-3.
© R. Paselk