Humboldt State University

Robert A. Paselk Scientific Instrument Museum

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Abbe Refractometer


Ser No 2009


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The Spencer Lens Company began selling an Abbe refractometer in about 1920. Catalog illustrations differed from the current instrument in having a tripod base and a gear-drive alidade. The base was redesigned by 1924, as illustrated in catalogs, and as seen in the Spencer instrument in this exhibit. AO-Spencer replaced the rack and pinion alidade drive with a clamp and slow motion screw around 1941, as shown in the Cenco 1941 catalog (the older rack and pinion form is still illustrated in the 1942 Fisher catalog). Around 1976 American Optical Co. (successor to Spencer) introduced an Abbe refractometer with digital readout of the refractive index. This easy to read instrument is still sold under the Leica name.

The current instrument was in use at Humboldt from 1953 until it was replaced in 1982 with a B&L Abbe 3L. This instrument is described in detail in the 1953 (?) American Optical Company Scientific Instrument catalog as item 10075, AO Spencer Standard Refractometer with Amici prisms. The catalog illustration provided comes from: Cenco. Cat J- 150 General Catalog Laboratory Apparatus & Scientific Instruments. Chicago. (1950). This instrument is also shown as item 73­563 - Refractometer - Abbe, with Amici Prisms on pg. 782 of the 1950 Adolf Frese Corp. Catalog. According to HSU Inventory this instrument was purchased in 1953 for $556.20.


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. A brief essay, The Chemical Refractometer, describes the characteristics, 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 11.5" high in the closed, vertical position. The base is of cast iron with black crinkle finish, some of which has come off to expose the iron below the mirror rail. The scale and readout arms are of brass held together with steel screws. All of the control knobs and the alidade handle are in heavy chrome plating. The solid metal (chrome plated?) two sided mirror is mounted on an adjustable dovetail slide. The scale is finely engraved on an inlaid German silver strip with scale divisions to the thousands place (nD 1,300­1,710), and numbered to the hundreds place on either side of the scale, allowing it to be read in either direction. The number: 788432618 is engraved on the scale just past 1710. The readout is viewed with an adjustable triplet magnifier. A hairline engraved on a glass window affixed via a threaded retaining ring to the prism alidade determines the index. The prism alidade has a tangent screw fine adjustment. The refractometer telescope is heavy black enameled brass, with the AO shield logo engraved and white filled on the arm over Spencer and the serial number: 2009. The Amici color compensating prism scale is finished in brushed chrome with black filled engraved divisions (0-60-0) and adjusted with a knurled wheel. The prism holder is finished in brushed chrome with polished chrome tubulatures for connecting to a circulating bath for temperature control. There is a chromed brass thermometer shield and mercury-filled thermometer. Engraved: HSU 43923.

A detailed description of this instrument is found in Chapter L, "Optical Measuring Instruments" of the 1950 American Optical Instrument Catalog.

The instrument has its original black leatherette covered hardwood case (14 in x 8 in x 8 in) and its original glass block refractive index standard (nD = 1.5179; 0.658" x 0.494" x 0.125", with one side and one end polished) in a small plastic vial (5/8" x 1 1/2" with AO molded into the inside of the cap). An instruction manual and a dispersion table accompanied the instrument.

1 According to Humboldt State University property records this instrument was aquired in 1953.

Refractometer Exhibit Catalog

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

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© R. Paselk
Last modified 23 August 2010