Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Humboldt State College (c. 19382)
The redesigned stand of this instrumant makes it stand out relative to the earlier Zeiss instruments. The new stand, introduced around 19113, is round with a curved limb, and made from japanned cast iron rather than the nickel plated brass of previous models. Other new features make the instrument more convenient for the user, including the reoriented scale and magnifier so that the telescope, scale, and magnifier all now face the user. The dispersion scale has also been angled so that it can be viewed with a slight movement of the eye from the telescope eyepiece. A handle has been added to the alidade, easing its adjustment. The catalog scan is taken from the Arthur H. Thomas Co. catalog, Laboratory Apparatus and Reagents. Philadelphia (1921).
The design of this instrument remained the basis of Carl Zeiss refractometers until 1950 with the exception of changes in the mirror mount and the alidade fine adjustment, as seen in the 1926 example in this exhibit.
The Abbe refractometer provides a quick and easy means for determining refractive index and dispersion of liquids and solids. Its most common use is the determination of the concentrations of solutions. It is used in the examination of organic compounds (oils, solvents, etc.), solutions, food products, and serum protein concentration. The refractive index is measured by aligning the crosshairs in the telescope with the line of total reflection. This line is moved by rotating the prism assembly with the alidade. Reading at constant temperature is important, thus the prisms are enclosed in a water jacket which may be connected to a constant temperature bath.
Ernst Abbe published his Neue Apparate.... (1874)4 in which he discussed the theory and described instruments for the measurement of refractive index using prisms and by total reflection. It is here that he first describes the Abbé refractometer for determining the refractive index of fluids. This initial instrument includes Amici prisms and is essentially the same as a modern Abbé refractometer, though without temperature jacketing. An instrument very similar to that described by Abbe in 1874 was shown in catalogs beginning in 18935, shortly after the formation of the Instrument Department of the Carl Zeiss works in 1890.6 This style, with slight modifications7, continued to be seen in catalogs at least until 1910. A new design, apparently identical to the specimen in this collection, appears in a catalog of Zeiss instruments exhibited in Dresden in 1911.3 This instrument appears in catalogs at least as late as 1927.8 By 1934 this design had been modified by placing the mirror on a swinging arm attached to the prism axis and by adding a rack and pinion adjustment to the alidade.
A brief essay, The Chemical Refractometer, describes the charecteristics, design, and use of these instruments. A detailed history, The Evolution of the Abbe Refractometer, traces the development of this valuable instrument to around 1980.
The instrument stands 11 1/2" high in the closed, vertical position. The round, cast iron base is 5 1/2" diameter. The curved edge of the base is black japanned, while the top is finished in a fine black crinkle enamel. The post is heavy cast iron, finished in crinkle enamel, and bolted to the base from below with three heavy screws. There is a small (1/2" x 11/16") plaque attached to the base with four screws with the Carl Zeiss Jena "lens " logo with Germany written beneath. The logo is also engraved and black-filled on the telescope arm, along with the serial number: Nr.15645. The inlaid nickel silver scale has black-filled graduations to the thousands place, with numbering to the hundreds-place. The tenths-place is also numbered, with larger numerals (1,X) at the even-numbers, and is carried on a black japanned iron (or steel) arm. The alidade is black crinkle finished brass. The telescope, telescope arm and other furniture are nickel plated, while the prism holder/heating block has a flat black oxidized coating. There is a small, square, watch-key type shaft for adjusting the Amici prisms in the side of the telescope. The original thermometer holder has been replaced with a custom brass adaptor to fit rubber stoppers. The instrument is engraved on the telescope arm: HSC 5374.
The instrument is in its original light hardwood ("alderwood") case (8 1/4 x 6 3/4 x 14" h), with a black painted iron carry-handle and nickel plated keyhole cover.
Research: A refractometer apparently identical with this specimen is illustrated in a catalog of Zeiss instruments exhibited in Dresden in 1911.3 This instrument appears in vendor catalogs at least as late as 1927.7A similar instrument, by Carl Zeiss, Jena, but with a gear drive for prism movement and the mirror mounted on the prism axis instead of the base, is illustrated in the Braun Corp. Catalog 34 (1934) as items 55630/1 on pg 654. A completely new & different model from Carl Zeiss is described in the Braun-Knecht-Heimann-Co. div of Van Waters & Rogers, Inc, Catalog No. 63 (©1961) on pg 885. HSU computer records indicate that this instrument was acquired in November of 1956, however, the HSC property number and its appearance in the HSC inventory book with other instruments acquired by Humboldt in the mid- to late 1930's indicate it was actually purchased c. 1938.
1 "No. 15645 was produced before February, 19., 1920 and delivered to Sussfield, Lorsch & Co. in New York on February 27 1920." Personal communication (1998), Dr. Wolfgang Wimmer, Archivar, Carl Zeiss Jena GMBH.
2 Current HSU inventory records (1998) indicate that this instrument was acquired in November of 1956, however, the HSC property number and its appearance in the HSC inventory book with other instruments acquired by Humboldt in the mid- to late 1930's indicate it was actually purchased c. 1938.
3 Carl Zeiss Optical Works. Catalogue to the Collection of Optical Instruments Exhibited by the Carl Zeiss Optical Works Jena. Dresden International Hygiene Exhibition (1911) pg 13.
4 Abbé, E. Neue Apparate zur Bestimmung des Brechungs - und Zerstreuungsvermögens fester und flüssiger Körper. Mauke's Verlag, Jena (1874) Taffel: Fig. 5-7.
5 Carl Zeiss Optical Works. Optical Measuring Instruments. Carl Zeiss Optical Works, Jena (1893) pp 9, 10.
6 Auerbach, Felix. The Zeiss Works and the Carl Zeiss Foundation in Jena. (English translation by R Kanthack) W. & G. Foyle, Ltd, London (1925).
7 Zeiss. Abbe's Refractometers. 3rd Edition (Mess. 172). Carl Zeiss, Jena (1907) pp 2 & 9.
8 Cenco. Laboratory Apparatus for Chemical, Industrial, Metallurgical, Bacteriological, Board of Health, Clinical, Hospital and Commercial Testing Laboratories. Catalog C. Central Scientific Company, Chicago (1927) pg 592. The engraving in this catalog appears to be identical to the one used in 1911 in reference 10, above.