Perkins — Molecular Weight of Radium Emanation. 469 



Jan. 31, 



at 275 



° C. 



Feb. 1, 



at 



275 



°C. 



Time after 







Time after 









pump began 





k 



pump began 







k 



in min. 







in min. 









15 





•0379 



15 







•0387 



20 





•0372 



20 







•0389 



25 





•0368 



25 







•0378 



30 





•0368 



30 







•0378 



35 





•0366 



35 







•0382 



40 





•0371 



40 







•0380 



45 





•0366 



45 







•0378 



Feb. 11, 



at 25C 



C. 



Feb. 12, 



at 25C 



° C. 



Time after 







Time after 









pump began 





k 



pump began 







k 



in min. 







in min. 









15 





•0349 



15 







•0344 



20 





•0344 



20 







•0347 



25 





•0342 



25 







•0344 



30 





•0342 



30 







•0347 



35 





•0342 



35 







•0347 



40 





•0337 



40 







•0344 



45 





•0339 



45 







•0347 



The decay curves plotted from the results of the above 

 experiments are indistinguishable from those obtained for the 

 active deposit from radium. 



The following tables give the times of collection in min. 

 and the amounts diffusing per min. in grs. when a constant 

 supply of mercury vapor from about 300 grs. of mercury was 

 kept in the diffusion chamber : 



Feb. 



3, at 250° C. 





Feb. 4, at 250° 



C. 





Feb. 6, at 250° C. 



Time Am 



ts. diffusing 



Time 



Amts. diffusing 



Time 



Amts. diffusing 



ing 



rs. per min. 





in grs. per min. 





in grs. per min. 



45 



•00450 



26 



•00447 





60 



•00456 



46 



•00452 



50 



•00449 





40 



•00454 



67 



•00445 



40 



•00446 





102 



•00451 



64 



•00446 









30 



•00445 



31 



•00450 



50 



Feb. 5, at 250 c 

 •00468 



c. 







Feb. 



6, at 250° C. 







At 275° 



C. 



Time 



Amts. diffusing 





Date 



Time 



Amts. diffusing 





in grs. per min 











in grs. per min. 



55 



•00468 





Feb. 4 



36 





•0102S 



50 



•00444 





a 



30 





•01003 



50 



•00451 





Feb. 5 



26 





•01021 



60 



•00459 





Feb. 6 



60 





•00981 



As the ground ends of the collecting tubes were heated, in a 

 Bunsen flame, to about the temperature of the furnace' each 

 time before insertion, very slight changes took place in the 



