Humboldt State University
Robert A. Paselk Scientific Instrument Museum
Wm. Gaertner & Co.
Humboldt S-T-C; c.1926
The oldest optical method for chemical analysis, Bunsen and Kirchhoff introduced spectroscopy as a laboratory method in 1860. The basic features of the spectroscope (or spectrometer) include a slit and collimator to produce a parallel beam of light which then falls on the dispersive element (a prism or grating). The resulting spectrum is then observed through a telescope. Spectrometers are particularly valued in two types of studies: 1) The identitfication and quantification of elements by the observation of line spectra (emission or absorption), 2) The identification and quantification of substances by the observation of absorption bands.
Gaertner small model spectroscope. The graduated aluminum circle is 125mm dia, with divisions every 30' and two verniers reading to 1'. A black japanned brass plate protects the graduated circle, having oval cutouts at 180° for reading the verniers. The instrument is stamped on the plate in white filled letters: WM. GAERTNER & CO / CHICAGO / 323. The circle with the attached telescope and the vernier plate move independently, and are both equipped with clamp and tangent screws. The aluminum prism plate is 80mm dia, and is fitted with leveling screws and a clamp for the prism (missing). The telescope and collimator are each held in a cast iron double cradle by five adjusting screws: two near the objective provide a pivot, while the remaining three provide horizontal and vertical angular adjustment. The entire instrument sits on a substantial cat iron tripod. All adjusting screws are of polished nickel plated brass with checkered knurling. The telescope and collimator each have 25mm objectives and 160mm? focal length. The slit has nickel silver jaws, adjusted by a screw to the side (replacement). The telescope focuses by means of a knurled ring. The eyepiece is equipped with a beam splitter accessed through a hole to the right side for superimposing scales etc. on the spectral image. An oval brass tag, attached with brass pins to the opposite right of the collimator, is stamped: HUMBOLDT S-T-C / 2103.
Bennet, J. A. The Celebrated Phaenomena of Colours: the early history of the spectroscope. Whipple Museum of the History of Science, Cambridge (1984).
Brand, John C. D. Lines of Light: The Sources of Dispersive Spectroscopy, 1800-1930. Gordon and Breach Publishers (1995)
Minor, Ralph S., Physical Measurements, A Laboratory Manual in General Physics for Colleges: Part 2, Magnetism and Electricity, Sound and Light 3rd ed, Associated Student's Store, Berkeley (1956) pp. 118-121, 122-124, 158-159.