An accessory designed and constructed for use with the Perkin-Elmer double-beam Model 21 spectrophotometer is described, which permits the measurement of spectral emissivities of opaque materials at room temperatures. The measurements made are of total (specular plus diffuse) spectral reflection. From this value the spectral emissivity is obtained by subtraction from one.
The new source consists of a heated enclosure to supply the energy and a twin optical system to lead the respective sample and reference beams into the instrument. Part of this optical system is removable to permit normal operation of the spectrophotometer and replaceable without readjustment. A temperature-controlled water supply is used to cool the sample.
A method for extending the use of this equipment to measure emissivities of materials of low conductivities has been outlined.
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