Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Adam Hilger introduced an Abbe refractometer around 1918, as indicated by the October 1, 1918 date on their descriptive leaflet, the December 1918 date on their refractometer manual, and the lack of a listing for the Abbe refractometer in their 1914 instrument catalog. The current instrument is vintage 1920 as indicated by the 1919 dates for the dispersion table and thermometer certification. The Hilger design is very conservative, copying the earlier Carl Zeiss design of the turn of the century to give an instrument of almost identical appearance (see Zeiss 1910), as compared to the contemporaneous instruments of Zeiss (introduced c.1911) and those of Spencer and B&L, as seen in the catalog illustration above. However, Hilger does include the reoriented scale and magnifier facing the user and the angled dispersion scale which Zeiss introduced in their 1911 redesign. The catalog scan is taken from the Arthur H. Thomas Co. catalog, Laboratory Apparatus and Reagents. Philadelphia (1921).
Use/History: 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.
Description: The instrument stands 12 3/4" high in the closed, vertical position. The base is of japanned cast iron, 4 1/2 x 3 1/2 x3/4 in. The remainder of the instrument is of heavy brass with japanned finish, except for the telescope tube and various fittings which are lacquered in an orange-gold color, and the knob for latching the prism assembly which is nickel plated. The refractive index scale is finely engraved on a nickel-silver inlay. The dispersion scale is also engraved on nickel silver, with positive numbers (0-25-0) filled with red enamel and negative numbers (0-25-0) filled in black. The fiduciary line is also engraved on a small section of nickel silver. The instrument is labeled (white filled engraving) on the telescope bracket: ADAM HILGER LTD, and on a second line beneath: LONDON, ENGLAND. The serial number is engraved on the inside of the telescope arm: No M46.304, second line: 19203.
The instrument has its original fitted mahogany case (14"h x 6 1/2"w x 6 1/4"d) with an apparently original bottle of monobromonapthalene, (3 1/4 in h to top of stopper) glass test block, (nD = 1.5174; 0.605" x 0.456" x 0.168", polished on one side and one end) original thermometer with National Physical Laboratory Certificate (the thermometer is frozen in the thermometer shield so it cannot be determined that the certificate in fact goes with this thermometer), instruction manual, and heavy cardboard Dispersion Table.