Humboldt State University
Robert A. Paselk Scientific Instrument Museum
"Abbe 3L" Refractometer
Bausch & Lomb
Serial No. HD3489
The Abbe 3L was introduced by Bausch and Lomb in 19562 "Any instrument of the Abbe type consists of (a) a refracting prism system (b) an appropriate scale, (c) a compensation system consisting of Amici prisms which permit the use of white light, and (d) a telescope with crosshairs which permit the borderline of total reflection to be observed and set precisely. This instrument differs from conventional types in that the refracting prism is fixed and horizontal and that the observing eyepiece is directly above the measuring prism.A pivoted mirror is used to move the total reflection dividing line. The index scale is attached to this moving mirror. A single eyepiece is used to observe both the total reflection field and the scale."3 This particular instrument was used by the Humboldt State University Physics Department. An identical instrument (Serial No. PD9243; 19581) was used in the Chemistry Department in the physical chemistry laboratory and is now (2007) in the biochemistry laboratory. A newer model, with a single course-fine control is currently (2007) in use in Humboldt's organic chemistry course. The catalog scan is courtesy of Van Waters and Rogers, Catalog 69 Scientific Apparatus instruments and supplies for: Industrial, Educational, Clinical and Research Laboratories. San Francisco (1968) p 876.
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 12 3/4" high in the closed position, and the base is 11" x 5 1/4" in its greatest dimension. The instrument is constructed from a hollow, heavy aluminum casting. The right side of the casting, open to allow access to the optics and mechanism (see Figure 5 on p10 in the manual), is covered by a thin aluminum sheet-metal cover. The instrument is painted in a heavy, grey enamel, with exposed metal parts nickle or chrome plated. The dispersion adjustment wheel is located under an acrylic plastic window just beneath the telescope. The refracting prism is fixed, and horizontal, allowing for very convenient specimen application.
The instrument is in its original light hardwood case (15"h x 13" d x 8 1/2" w) and includes a reference manual, an Inspection Certificate (cover, inside) a thermometer (attached to the instrument and visible in the photo), a glass test block (nD = 1.5129; 0.807" x 0.472" x 0.148"; one side and one end are polished) and a bottle of 1-bromonapthalene.
1 After 1941 B&L went to a letter system for serial numbers, with two letters preceeding the serial number. The first letter is the date letter, while the second is a class designation. Personal communication, Stuart Warter, California State University, Biology Dept., Long Beach State University (1998). The date letters are tabulated in Bracegirdle, Brian. Notes on Modern Microscope Manufacturers. Quekett Microscopical Club, Oxford (1996).
2 The reference manual for this instrument, Bausch & Lomb Abbe-3L Refractometer Reference Manual, has the code VIII-56 on the back cover, which experience leads me to believe a publication date of August 1956. The Abbe-3L is also illustrated as a related instrument in the Bausch & Lomb Spectrograph brochure dated Dec. 1956, while the 1955 Chemical Rubber Company Catalog A-L still advertises the Abbe 56 as B&L's refractometer (personal communication, Bill Burns, Long Island NY).
3 Bausch & Lomb Abbe-3L Refractometer Reference Manual, p 6 "Description of the Instrument."