. Archives of physical medicine and rehabilitation . o raise or to lower the vacuumby means of palladium tubes. Obviouslyin this tube, the residual gas must behydrogen. In the same section, how-ever, it was stated that the gasesliberated from the ordinary vacuumregulators, are carbin dioxide and watervapour. Which gas, therefore, if any,is the most suitable? Is there any de-cided advantage in one over all theothers? Consider, first, the question ofconstancy of vacuum. We have seenthat, because of the adsorption of theresidual gas by the walls of the tube,as well as by metal surfaces inside it,
. Archives of physical medicine and rehabilitation . o raise or to lower the vacuumby means of palladium tubes. Obviouslyin this tube, the residual gas must behydrogen. In the same section, how-ever, it was stated that the gasesliberated from the ordinary vacuumregulators, are carbin dioxide and watervapour. Which gas, therefore, if any,is the most suitable? Is there any de-cided advantage in one over all theothers? Consider, first, the question ofconstancy of vacuum. We have seenthat, because of the adsorption of theresidual gas by the walls of the tube,as well as by metal surfaces inside it,there is always a progressive hardening. TABLE V. Atomic Atomic Melting Thermal Specific Volatilization Metal Weight Number Point Conductivity Heat detectable at PIrtinum 78 I750°C .03 I200°C Iridium 77 2290°C .03 I400°C Osmium 76 2700 C .03 2300°C Tungsten 184 74 3300 C .03 1800°C Tantalum 181 .5 73 2900 C .04 Molybdenum 96 42 2500 C .07 Copper 29 1084 C .09 Nickel 28 !450°C .10. Fig. 237 X-RAYS AND X-RAY APPARATUS-
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