. The interpretation of radium and the structure of the atom . to detect theproduction of helium from the primary radio-elementsuranium and thorium, and succeeded in proving inboth cases that helium is produced, and, moreover,that the rate of production is almost exactly what is tobe expected from the theory of atomic quantity is about one five-hundred-thousand-millionth of the mass of the uranium or thorium perannum ! A photograph of the apparatus employed,as it stood in the Physical Chemistry Laboratory, isshown in Fig. 26. These are seven exactly similararrangements side
. The interpretation of radium and the structure of the atom . to detect theproduction of helium from the primary radio-elementsuranium and thorium, and succeeded in proving inboth cases that helium is produced, and, moreover,that the rate of production is almost exactly what is tobe expected from the theory of atomic quantity is about one five-hundred-thousand-millionth of the mass of the uranium or thorium perannum ! A photograph of the apparatus employed,as it stood in the Physical Chemistry Laboratory, isshown in Fig. 26. These are seven exactly similararrangements side by side, each of which is quite separateand unconnected with the others. Each consistsessentially of a large flask, capable of holding a con-siderable quantity of the material experimented uponin the form of solution. Each is provided with a peculiarform of mercury tap, which, while it serves perfectlyto keep out the atmosphere from the flask for an in-definite time, can at any moment be opened by suckingdown the mercury in the barometer tubes, so that the. w :i 0. S To face p. loo PRODUCTION OF HELIIBI FROM URANIIBI 101 accumulated gases from the flask can be extracted andtested for helium without admitting air. Air has beenthe great trouble. A pins-head-full of air left in thewhole of the large flask or in the solution, or leakingin during the periods of accumulation, would completelyruin the experiment. Most of the elaborations of theapparatus have to do with .the preliminary thoroughremoval of the air from the apparatus before the ex-periments are commenced. The methods of testing forhelium are also entirely new. They depend on thepower I found was possessed by the metal calcium, whenheated to a very liigh temperature in a vacuum, of ab-sorbing the last traces of all gases except the gases ofthe helium and argon type. In this way the minuteamount of helium produced (usually not more than athousandth part of a cubic millimetre) is freed perfectlyfrom every other trace of ga
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectradioac, bookyear1922
