1904.] On the Production of Helium from Radium. 



353 



Fig. 5. 



hence the spectrum tube contained , 000052 c.c, or 0*052 cub. mm. 

 The total quantity obtained was twice this amount, or 0*1 cub. mm. 



As 1 litre of helium weighs 0*18 gramme, for its density is twice 

 that of hydrogen, 0*1 cub. mm. weighs 0*000018 milligramme. This 

 amount is the product of 50 milligrammes of radium bromide in 

 60 days; hence, 1 gramme of the bromide should give in a year 

 0*0022 milligramme. It should be mentioned that the spectrum of 

 argon was present, and it may have seriously interfered with this 

 estimation. The helium, too, may have penetrated and been retained 

 in the glass. 



Experiment 4. — It appeared feasible to 

 attempt to measure the actual volume of 

 the emanation in a fine capillary tube. 

 Thinking that any bought capillary tube 

 would be too wide, we drew a very 

 narrow one, which had an electrode 

 sealed into its end. It turned out, how- 

 ever, to be very irregular, and the results 

 as regards volume are not very trust- 

 worthy. A is the capillary tube, with a 

 platinum electrode of very fine wire 

 sealed into its upper end • the mixed 

 hydrogen and oxygen containing the 

 emanation were introduced into the ex- 

 plosion burette F through the inverted 

 syphon E ; some moist caustic potash 

 had been melted in the top of the burette, 

 so as to remove from the gases any pos- 

 sible carbon dioxide which might have 

 been produced by the flame causing an 

 organic dust in the burette to burn. After 

 the gases had been exploded, the excess 

 of hydrogen, together with the emanation, was allowed to stand for 

 some time in contact with the caustic potash. The upper part of the 

 apparatus having been completely evacuated, the connection with 

 the pump was closed, and the tube leading to the reservoir of the 

 burette was clipped; on making communication by turning the tap 

 of the burette, the hydrogen and the emanation entered the apparatus. 

 Liquid air was then poured into the tube G, so as to cool the bulb B, 

 where the emanation condensed. After raising and lowering the 

 reservoir of the burette several times, in order to convey the emana- 

 tion into the bulb B, the tap of the burette was closed, and that 

 leading to the pump opened. Again opening cautiously the tap of 

 the burette, the mercury was allowed to rise, passing through the 

 tube D containing phosphorus pentoxide as far as G ; the evacuation 



