126 



W. Duane — Effect of a Magnetic Field 



fected methods used by Ramsay and Soddy in their early 

 experiments on helium, and the purification of the emanation 

 in which the oxygen and hydrogen were absorbed by red 

 hot copper and copper oxide, the carbon dioxide by caustic 

 soda and the water vapor by phosphorus pentoxide, and the 

 traces of gas remaining were removed by a vacuum pump after 

 condensing the emanations by means of liquid air. 



The apparatus is represented in fig. 2. The bulb A contains a 

 solution of over "3 gram of RaCl 2 , kindly placed at my disposal 

 by Madame Curie, and the emanation is allowed to accumulate 



Fig. 2. 



To ryercury pump 



AL 



To Water />umh N ^- 





TT 





§88888 



IE 



in it with the stopcock B closed. When about to begin the 

 purification, the mercury in the tubes C is lowered, and a 

 good vacuum produced by means of the mercury pump. 

 Toward the end of the pumping the tubes to the right of the 

 caustic potash, including the copper and copper oxide, are thor- 

 oughly heated in order to expel all gases as far as possible. 

 After a high vacuum has been obtained the mercury pump is 

 cut off by letting the mercury rise in the tubes C, and the stop- 

 cock B is opened, allowing the gases from the solution, carry- 

 ing with them the emanation, to enter the large reservoirs D 

 and the purifying tubes. To absorb the oxygen and hydro- 

 gen the part of the tube containing the copper and copper 

 oxide must be heated to a very dull red, and during the 

 process, the stopcock B being closed, the mercury from C is 

 allowed to rise into D, filling it and the tube up to the caustic 

 potash. The stopcock F may be used to regulate the flow of 

 gas into the purifying tubes. If desired, the small quantity of 



