The refractive indices of a 31° prism of silver chloride were measured at 30 wave-lengths at a constant room temperature of 23.9°C, from 0.578 to 20.6μ by use of a minimum-deviation spectrometer and a Perkin-Elmer infra-red spectrometer equipped with a calibrated screw for operation of the Littrow mirror. A cadmium-mercury lamp was the source from 1 to 2μ. From 2 to 20μ a Globar was used as the source with various Baird’s reflection interference filters and the absorption bands of carbon dioxide, carbon disulfide, water, methylcyclohexane, polystyrene, trichlorobenzene, and chlorobenzotrifluoride for the identification of wave-lengths. In the visible region two prisms, one pressed and polished, the other sawed and lapped, were used and the results compared. The sensitivity of index to temperature is approximately −6.1 × 10−5 per centigrade degree for wave-length 0.610μ.
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