Investigations in the infra-red region of the spectrum. Part VI.—The absorption spectra of the dioxides of chlorine and sulphur

Abstract
The infra-red spectrum of chlorine dioxide has not been previously determined, although its photochemical properties and its electronic band spectrum have been the subject of recent extensive enquiry. From the latter attempts have been made to interpret the band spectrum, and to assign values to the characteristic frequencies of the fundamental modes of vibration in the ground electronic state. It will be seen from the following that the values so deduced are incorrect, and it is probable that in no case of a polyatomic molecule is a complete determination of its fundamental frequencies possible without resort to its infra-red spectrum. Experimental . The method of preparation described by Goodeve and Stein ( loc. cit. ) was followed. The gas passed under water-pump vacuum to a trap immersed in a carbon dioxide-acetone freezing mixture; it was then distilled through phosphoric oxide tubes and condensed in a second trap cooled by liquid air. This trap could be removed from the generating system by means of a glass seal and a spherical glass joint; the ground joint was of universal pattern and the trap containing the dioxide could therefore be readily transported and connected to the absorption tube system. The latter was of as small capacity as possible, and no manometer was included, pressure in the absorption tube being regulated by immersing the dioxide trap in a freezing mixture of known temperature. The greatest pressure used during the investigation was the vapour pressure of the gas at 0° C., or approximately 630 mm. The length of the absorbing column of gas was in all cases 45 cm.; the lubrication of taps and of joints between the rocksalt end plates and the absorption tubes was effected by chlorinated vaseline.

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