On the viscosities of gaseous chlorine and bromine

The Object of the Experiments about to be described was to determine the viscosities, at various temperature, of gaseous chlorine, bromine, and iodine, by comparison with air. The apparatus, however, proved unsuitable in several respects for working at higher temperature required. It has, nevertheless, yielded satisfactory results at the lower temperatures ; and the viscosity of chlorine at atmospheric temperature and at 100° C., and that of bromine at the latter temperature only, have been measured by means of it. These values are now published, pending the extension of the investigation on the lines indicated, with a new form of apparatus which promises to be entirely adequate for the purpose. The chief difficulty which presents itself in working with the halogen gases is the readiness with which they attack mercury. On this account, the method I Have previously used* for viscosity determinations was rendered unsuitable; but it has found possible to retain one of its most desirable features, viz., the mercury pellet, which serve the double purpose of creating a constant pressure difference, and of measuring the volume of gas emerging from capillary. In other respects the apparatus is quite different, the main object in its construction being to prevent contamination of the mercury. This has been sufficiently secured by causing the pellet to aspirate the gas through the capillary tube, with a deep layer of air acting as a kind of buffer between them. The failure of the method at high temperature was chiefly due to the mercury pellet becoming unstable, owing to the diminution of surface tension.