A long path gas absorption cell especially suited for infrared analyses of components of extremely low concentrations and absorption coefficients is described. The cell can be evacuated or pressurized. With aluminized mirrors and KBr field lenses, the evacuated cell performs with a peak efficiency of 45 percent of incident energy at 10 meters path length. Path length is adjustable by 1.25-meter increments from 1.25 meters to 10 meters. Adjustments are simple and can be made in a matter of a few minutes with good reproducibility. The cell will attach to the Perkin-Elmer Models 12, 112, and 21 spectrometers with compatibility to other attachments. The optical path can be altered quickly so that the usual sampling space of the spectrometer is available.
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