Usage/History: The Abbe refractometer provides a quick
and easy means for determining refractive index and dispersion
of liquids and solids. 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)2 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 18933, shortly after the formation of
the Instrument Department of the Carl Zeiss works in 1890.4
This style, with slight modifications5, 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 1911.6
This instrument appears in catalogs at least as late as 1927.7
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.
Early descriptions of the features and use of the Abbe
refractometer are provided below:
Description: The instrument stands 11.5" high
in the closed, vertical position. The base is of cast iron with
polished black enamel on the coved edge and the remainder in
crinkle finish. There is a small tag affixed to the base with
screws inscribed with the Carl Zeiss Jena "achromatic lens"
logo, with Germany beneath it. The scale and readout arms are
of steel. The scale is engraved on an inlaid German silver strip
with scale divisions to the thousands place (nD 1,300-1,700),
and numbered to the hundreds place. Readout is via a hairline
engraved on a glass window affixed with screws to the readout
arm beneath an adjustable magnifier. The refractometer telescope
is heavy nickel-plated brass, with the Zeiss logo engraved on
the front over the serial number: Nr. 15645. The Amici color
compensating prism scale is black enameled with white filled
engraved divisions (0-60-0) and adjusted with a knurled wheel.
The prism holder is in flat black enameled brass with tubulatures
for connecting to a circulating bath for temperature control.
There is a screw-in brushed brass thermometer holder on the upper
rear bath connection (shop made at Humboldt?). Miscellaneous
hardware and screws are nickel-plated. Engraved: 5374 HSC.
The instrument is in its original light hardwood (maple?)
case (8 1/4 x 6 3/4 x 14" h), with a black painted iron
carry-handle and silver plated keyhole cover.
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. However,
see Research above.
2 Abbé, E. Neue Apparate zur Bestimmung
des Brechungs - und Zerstreuungsvermögens fester und flüssiger
Körper. Mauke's Verlag, Jena (1874) Taffel: Fig. 5-7.
3 Carl Zeiss Optical Works. Optical Measuring
Instruments. Carl Zeiss Optical Works, Jena (1893) pp 9,
10.
4 Auerbach, Felix. The Zeiss Works and the
Carl Zeiss Foundation in Jena. (English translation by R
Kanthack) W. & G. Foyle, Ltd, London (1925).
6 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.
7 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.
