Usage: 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). The resulting
spectrum is then observed through a telescope. In the Bunsen
spectroscope the relationships of the telescope and collimator
are fixed at angles appropriate to viewing the visible spectrum
through a prism. The telescope may be adjusted slightly to center
appropriate segments of the spectrum. The third tube is a scale
telescope which is used to project an image of a scale. The image
is reflected off the face of the prism in such a way as to superimpose
itself onto the spectrum for ease of measurement. This example
is a student instrument for the determination and analysis of
spectra using either a prism or grating.
Some early descriptions of the spectroscope and its use are
provided below:
"The
Spectrometer" in Minor. Physical Measurements:
... Sound and Light (1917)
Description: The instrument stands 15" high at
its highest point. The legs of the tripod extend 6" from
the center of the column. The prism box is 4" O.D. and 1
3/4" high. The prism table is mounted off-center, with three
screws for leveling against coiled tension springs. The cast
iron stand and the prism box are finished in black crackled lacquer.
There is a 60° prism on the prism table. The telescopes and
collimator are each an inch in diameter. The telescope may be
rotated though a short angle and clamped in place via a screw
clamp to the column. According to the catalog description the
objective lenses of the telescope and collimator are of 125 mm
focal length, the ocular is 14x, and the scale is 15 mm long.
The telescope, collimator, scale telescope and lid of prism box
are all finished in gloss black enamel. There is a yellow decal
on the column: STATE OF CALIFORNIA / HUMBOLDT COLLEGE / 15782.
A manual for the spectroscope was stored in the HSU analytical chemistry prep-room file drawer.
Research: According to HSU property records this instrument
was purchased in 1957 for $140.40. Bausch and Lomb published
a brochure (copy in Smithsonian NMAH Library) in 1932 entitled
New Bunsen Spectroscope, apparently introducing this style
of instrument to their line at this time.
