Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Sugar & Oil Refractometer
Chemical Heritage Foundation
Carl Zeiss introduced the sugar and oil refractometer in 19262, replacing the sugar refractometer. (The butter refractometer remained in production.) The Sugar and oil Refractometer is a specialized version of the Abbé refractometer designed specifically for work with sugar solutions in a production environment. The optics are nearly entirely enclosed and protected from the environment. The prism is horizontal and hinged at teh side, making it very convenient and easy to use. It has a revolving triple-prism compensator, like that in the Dipping refractometer, which is adjusted by a lever on the alidade. The placement of all controls is very convenient. The scale is engraved on a glass window. The narrow scope of the instrument enabled Zeiss to optimize the instrument in a number of ways. The narrower refractive index range (1.33 - 1.54 vs. 1.3 - 1.7) allows the use of a harder, lower refractive index glass for the prisms to give a more robust instrument. The narrow range also allows for easier readability and accuracy by spreading the range out over the readout arc. The scale (% solids for sugar and refractive index for oils) is engraved on a glass window. The illumination is very bright. Tilton and Taylor note that "The illumination for total reflection is particularly well arranged, and the enclosure of telescope, etc. results in but little scattered and nonuseful light." As a result the instrument is particularly effective for dark oils and syrups which use total reflection. The catalog scan is taken from the Arthur H. Thomas Co. catalog, Laboratory Apparatus and Reagents. Philadelphia (1921).
The sugar and oil refractometer is one of a variety of specialty designs adapting the Abbé design for specific purposes of the laboratory and/or industry. Tilton and Taylor note this instrument as "particularly different in apperance" and that it is an industrial model for sugars and oils. A brief essay, The Chemical Refractometer, describes the characteristics, design, and use of various refractometers. A detailed history, The Evolution of the Abbé Refractometer, traces the development of the predecessor to this more specialized instrument.
The instrument consists of a heavy brass cylindrical housing 4 13/16" diameter by 1 3/4" thick. The mirror is a replacement from an unknown microscope maker. The stand is custom made for display purposes since the original stand is missing.
The instrument is in its original light hardwood case ("alderwood"3) ( 10 1/16" x 7 5/8" x 5 1/2" h), with a black hard-rubber(?) coated steel carry-handle and nickel plated keyhole cover. The mirror is a replacement. The stand is custom made for display purposes since the original stand is missing. The case is fitted for the instrument and its accessories without provision for the stand. The stamped sheet-steel key is stamped "-CORBIN CABINET LOCK CO-" "NEW BRITAIN CONN U.S.A." and appears to be original. There is a Sargent and Company Chicago decal on the top of the case.
1 "Nr. 49734 is a sugar refractometer which was produced and sent to New York in April 1936." Personal communication (2004), Dr. Wolfgang Wimmer, Archivar, Carl Zeiss Jena GMBH.
2 Carl Zeiss (internal document) Entwurf zu einer Chronik der Abteilung Mess (An Outline of the History of the Measurement Division).
3 As noted on p 2 of the Carl Zeiss Sugar Refractometer instruction manual.
Tilton, Leroy W. and John K. Taylor. "Refractive Index Measurement." in Physical Methods in Chemical Analysis Vol. 1, 2nd ed. ; Walter G. Berl, editor, Academic Press, New York.(1961) p 431.