Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Precision Abbe Refractometer
Chemical Heritage Foundation
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.
According to the Franklin Institute article1 describing this instrument, it was designed by Warren Valentine after a study of the Zeiss Abbe refractometer in 1917. However, the lack of available mechanics capable of the precision work and lack of optics, due to the war effort, prevented completion of the first instrument until 1919. This study and replication effort resulted in Valentine constructing a second instrument with improvements to both mechanical and optical components to provide greater stability and accuracy than the traditional Abbe design. The 1928 article describes both the "fourth decimal" Precision Refractometer and the "fifth decimal" Improved Precision Refractometer. The catalog scan is from Adolf Frese Co. Scientific Instrument and Laboratory Supply Catalog. Los Angeles, (1950).
A brief essay, The Chemical Refractometer, describes the characteristics, design, and use of these instruments. A detailed history, The Evolution of the Abbé Refractometer, traces the development of this valuable instrument to around 1980.
The instrument stands 14 3/4" high in the closed, vertical position. The base is a 5 7/8" diameter hollow casting. The entire instrument is made of heavy bronze castings or machined brass. The stand and prism housing are finished in dull black enamel, while the sector, alidade, and telescope are finished in black crinkle enamel. All exposed metal is chrome plated. The extraordinarily finely divided scale is protected by a cast bronze shield, requiring illumination by a built in "grain of wheat" lightbulb, and viewing though a small microscope. A small two-prong female plug of the back of the sector casting allows power to be provided to the bulb. An aluminum tag is labeled as follows: VALENTINE REFRACTOMETERS / RICHMONDVILLE, NEW YORK / SERIAL NO / 3016.
1 Valentine, W. P. (1929) J. Franklin Inst. 207, 116.