Investigations in the Far Infrared

An instrument is described for investigations of the reflectivity, transmissivity and emission of various materials over the spectral range 20 to 150μ. The following measurements are reported: Reflectivities of rough surfaces, galena, $\beta$-magnesia, zincite, stibinite, corundum, sphalerite, molybdenite and cuprite. Transmissivities of KBr, KI a layer of KCl evaporated on a lacquer film, a thin film of amorphous quartz, liquid C${\mathrm{Cl}}_4$, and powdered Al and Cu. Emission of liquid and solid NaCl near the melting temperature.