Production of Helium by Radium. 597 



radium salt, and the upper portion of the tube (fig. 3) con- 

 taining the bulb was sealed on. The object of having the 

 bulb in the upper extremity of this tube was to prevent the 

 escape of the radium solution through excessive boiling 

 later under diminished pressure. 



Fig. 3. 



This tube was closed at one end by one short piece of 

 thick-walled rubber tubing and a screw pinchcock. The air 

 was completely removed from the tube, and about 30 cubic 

 centimetres of a dilute solution of hydrochloric acid was 

 introduced through the rubber tubing in such a manner as 

 to preclude the admission of any traces of air. The radium 

 salt was now completely dissolved by gentle warming of the 

 tube and the gases were pumped out of this tube, through 

 small KOH and P 2 5 bulbs, and finally through a thin- 

 walled U tube cooled in liquid air (for removing the radium 

 emanation at this point) attached at (fig. 2). These gases 

 were combined with the gases previously pumped off and 

 the mixture was introduced into the gas burette B. After 

 passing sparks between the electrodes in B, the gases were 

 drawn through the copper oxide in T (heated to low redness) 

 and introduced into the measuring portion of the apparatus, 

 where the volume of the helium was determined in the manner 

 described under the first determination. The cycle of opera- 

 tions carried out in the measurement of this second quantity 

 of helium comprised three separate exposures to the cooled 

 charcoal, with the removal of any condensed gases from the 

 charcoal after each determination. The results obtained 

 were in excellent agreement and showed no such variations 

 at the start as had been observed in the first experiment, 

 when the removal of the hydrogen had not been com- 

 plete previous to the introduction of the gases into A. 



Phil Mag. 8. 6. Voh 22. No. 130, Oct. 191 1 . 2 R 



