Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Ernst Abbe constructed the first Abbe refractometer in 1869.2 In 1874, he published a comprehensive booklet3 where he discusses the theory and describes instruments for the measurement of refractive index using prisms and by total reflection. It is here that he first describes and illustrates the Abbe refractometer for determining the refractive index of fluids.
This initial instrument includes Amici prisms and has all of the essential features of a modern Abbe refractometer, though without temperature jacketing. Like other instruments developed at Carl Zeiss to support microscope manufacture, refractometers were initially produced mostly for internal company use. Beginning around 1881 refractometers were described and offered, though not illustrated, in Carl Zeiss microscope catalogs.4 For example, the No. 27 catalog of 1885 lists four refractometers including a "No. 75 Grosses Refractometer nach Abbe," corresponding to Abbe's original design.5 According to the 1893 "Optical Measuring Instruments" catalog "Until recently these instruments have only occasionally been supplied .... But ... instruments in this class are [now] regularly manufactured." 6
The current instrument is very similar to the refractometer first descibed and illustrated by Ernst Abbe in 1874:3
The original Abbe design seems to have been followed in detail with early instruments, as seen in the illustration in the1893 instrument catalog (below), and in the very early instrument (a Refractometer V, Nr. 68, produced October 9, 18807) held at the University of Nebraska-Lincoln.8 The Nebraska instrument is finished completely in laquered brass, with the scale-arm having a decorative patterned polish, and comes in a fitted case as in the current instrument, but with dovetailed joints.
A somewhat later instrument, Nr. 148, held by the Smithsonian Institute Museum of American History (delivered to J. Queen & Co. in Philadelphia on July, 2., 18909) is essentially identical to the example in this exhibit, except that laquered brass replaces the nickel plating in our 1893 example. Thus, by at least 1890 Zeiss had modified the refractometer readout by tilting the scale and adding a magnifier, matching these features in catalog illustrations beginning by at least 189910 (below; and see the 1906 instrument in this exhibit):
Both of these features make the instrument somewhat easier to use: the tilted scale does not require the user to reorient his/her head as much, and the magnifier makes it possible for the average user to read the very fine graduations of the scale without external aids.
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 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.
Description: The instrument stands 11" high in the closed, vertical position. The cast brass base is 3 3/8" x 2 7/8" x 11/16" with a 1 1/8", slightly concave round mirror in a metal holder. No. 162 Carl Zeiss Jena is engraved in the base. An inspection of the current polished brass surfaces it is evident that most of the instrument (base and stand, alidade, telescope, etc.) was originally nickel plated. The scale is polished brass with black filled graduations and numbers, the sector carrying the scale was originally black enameled, along with the mirror-furniture, the prism holder and the scale magnifier and furniture. Partial dismantelling of the instrument revealed that the amici prisms are mounted in pieces of cork.
The instrument is in its original mahogony case (10" x 5 3/4" x 5 3/8" h), which is carefully fitted to hold the folded instrument, with nickel plated keyhole cover.
1 "No. 162 was delivered to Schimmel & Co. in Leipzig on November, 11., 1891." Personal communication (1998), Dr. Wolfgang Wimmer, Archivar, Carl Zeiss Jena GMBH.
2 Wittig, Joachim. Earnst Abbe.
BSB B. G. Teubner Verlagsgesellschaft, Leipzig (1989) pg
3 Abbe, E. Neue Apparate zur Bestimmung des Brechungs - und Zerstreuungsvermögens fester und fluüssiger Körper. Mauke's Verlag, Jena (1874) Taffel: Fig. 5-7.
4 Personnal communication (1998), Dr. Helga Beez, Carl Zeiss Optical Museum, Jena.
5 Carl Zeiss Optical Works. No.
27 Mikroscope und mikroscopische Hilfsapparate der Optichen WQerkstätte
von Carl Zeiss. Jena (1885) pp 47-48.
6 Carl Zeiss Optical Works. Optical Meauring Instruments. Carl Zeiss Optical Works, Jena (1893) pp 9, 10.
7 Personal communication (2003), Dr. Wolfgang Wimmer, Archivar, Carl Zeiss Jena GMBH.
8 A photograph of this instrument available on-line at the Department of Physics and Astronomy Historical Instrument Gallery at the University of Nebraska-Lincoln.
9 Personal communication (1998), Dr. Wolfgang Wimmer, Archivar, Carl Zeiss Jena GMBH.
10 Carl Zeiss Optiche Werkstaette. Specialkatalog über Spectrometer und Refractometer für feste und flüssige körper; hilfsapparate. Carl Zeiss Optiche Werkstaette, Jena (1899) pp 39-43.