. Radio-activity . xperi-mental arrangement of the first method is shown clearly in Fig. slow constant stream of gas, entering at A, was passed througha copper spiral S, over 3 metres in length, immersed in a bathof liquid ethylene. The copper spiral was made to act as itsown thermometer by determining its electrical resistance. Theresistance temperature curve was obtained by observation of theresistances at 0°, the boiling point of liquid ethylene — 1035°,the solidification point of ethylene —169° and in liquid air. Thetemperature of the liquid air was deduced from the tables givenby Bal
. Radio-activity . xperi-mental arrangement of the first method is shown clearly in Fig. slow constant stream of gas, entering at A, was passed througha copper spiral S, over 3 metres in length, immersed in a bathof liquid ethylene. The copper spiral was made to act as itsown thermometer by determining its electrical resistance. Theresistance temperature curve was obtained by observation of theresistances at 0°, the boiling point of liquid ethylene — 1035°,the solidification point of ethylene —169° and in liquid air. Thetemperature of the liquid air was deduced from the tables givenby Baly for the boiling point of liquid air for different percentagesof oxygen. The resistance temperature curve, for the particularspiral employed, was found to be nearly a straight line between 1 Societe de Physique, 1903. VIII] RADIO-ACTIVE EMANATIONS 239 0° and — 192° C, cutting the temperature axis if produced nearlyat the absolute zero. The resistance of the spiral, deduced from 2I>Uivoltmeter Ammeter. To Earth Fig. 45. readings on an accurately calibrated Weston millivoltmeter, witha constant current through the spiral, was thus very approximatelyproportional to the absolute temperature. The liquid ethylene waskept vigorously stirred by an electric motor, and was cooled to anydesirable temperature by surrounding the vessel with liquid air. The general method employed for the radium emanation wasto pass a suitable amount of emanation, mixed with the gas to beemployed, from the gas holder B into the spiral, cooled below thetemperature of condensation. After the emanation was condensedin the spiral, a current of electrolytic hydrogen or oxygen waspassed through the spiral. The temperature was allowed torise gradually, and was noted at the instant when a deflection ofthe electrometer, due to the presence of emanation in the testingvessel T, was observed. The resistance, subject to a slight correc-tion due to the time taken for the emanation to be carried intothe test
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