1904.] On the Production of Helium from Radium. 355 



volumes, the pressures corrected for capillarity, and the products of 

 volume into pressure : — 



Length of 



Volume in 



Pressiu'e in 



Volume x 





mill mm 



mm. 



pressure 



6-80 



0-163 



132-4 



21-6 



2-30 



0-0552 



333-4 



18-4 



1-55 



0-0372 



518-1 



19-3 



1-20 



0-0288 



644-8 



18-6 



0-95 



0-0228 



765-8 



17-5 



2-55 



0-0612 



309-2 



18-9 



11-90 



0-372 



55-3 



20-6 



The mean value of the product is 19-3, and the volume at normal 

 pressure 0*0254 c.mm. The same afternoon, numerous readings 

 were taken, and it was found that the sticking of the mercury 

 in the capillary tube made it difficult to ascertain the true volume. 

 As the pressure, however, was first raised, and then lowered, the mean 

 cannot be far from the truth. Now, a most remarkable circumstance 

 must be chronicled. Whereas the emanation in the previous 

 experiment contracted during its whole life, in this experiment a 

 regular expansion was observed, rapid at first, and slowly falling off 

 from day to day. Between 5 minutes past 1 o'clock and 7 o'clock, the 

 pressure being kept constant at 55-3 mm., the value of P.V. increased 

 from 20-6 to 48*4. This was on January 20th. On the 21st, the 

 P.V. had increased to 71*2, and remained fairly constant all day, and 

 three small bubbles appeared in the thread of mercury, below the level 

 of the emanation. On the 22nd, the value of P.V. had diminished to 

 56'5, and the volume of the bubbles had increased to 2 - 7 mm. length 

 in the tube. On the 23rd, the emanation occupied practically the same 

 volume, but the length of the bubbles had increased to 4-1 mm. The 

 presence of these bubbles made it impossible to obtain correct readings, 

 for the " sticktion " of the mercury was much increased. On the 25th, 

 P.V. had further diminished to 5T2 and the length occupied by bubbles 

 had increased to 5 '5 mm. On Februarj^ 3rd, the bubbles were united 

 with the emanation; the value of P.V. was 132*5 and the volume of 

 the gas under normal pressure, 0*174 cub. mm. On the 9th, the 

 P.V. had increased to 166, and the volume at normal pressure to 

 - 224 cub. mm. Lastly, the volume of the gas was measured on the 

 12th at atmospheric pressure; it amounted to 0*262 cub. mm. The 

 level of the mercury was then lowered, and the gas pumped out, it 

 showed a brilliant spectrum of helium. The tube was then heated, and the 

 volume of the absorbed gas was - 103 cub. mm. at atmospheric pressure ; 

 it, too, showed the helium spectrum, but the tube punctured before 

 this could be confirmed. 



These results are somewhat inexplicable in the light of the former 



