Danysz and Duane — Electric Charges of a- and (3-Rays. 305 



For the same reason there cannot have been a diffusion of 

 the atoms of radium A, B, or C into the mercury a sufficient 

 distance to appreciably absorb the a-rays. 



The average value of the charge per curie is *363 e. s. u. per 

 second, and since, as we have seen, only '00400 of the rays pro- 

 jected in all directions pass through the hole C, the total charge 

 carried by all the a-rays from one curie of emanation with the 

 equilibrium amounts of radium A B C is 90*8 e. s. u. per 

 second. This is almost three times the charge 31'6 carried per 

 second by the a-rays from radium C alone, as measured by 

 Rutherford and Geiger,* and corresponds to three times as 

 many a-particles, those from the emanation and radium A as 

 well as radium C. 



It is well known that a number of important constants can 

 be calculated from the value of the charge carried by the 

 a-rays. Among them the following may be determined by 

 using accurately known data only : 



In the first place we may calculate the volume v of helium 

 produced per second by one gram of radium together with its 

 emanation and radium ABC, using simply the volume of 

 hydrogen liberated in the electrolysis of water. One ampere 

 liberates -123 cm3 of hydrogen per second at 15°, and therefore 

 if N is the number of molecules in l cm3 at 15° and e is the 

 elementary charge in e. s. u. 



Ne = 1*22 X 10 10 



Since each a-particle carries the charge 2e the total charge 

 carried by the a-particles from the gram of radium is %v1&e 

 per second. Remembering to add the a-particle from the 

 radium itself to those from the emanation and radium A and 

 C we have 



2Neu 



= 



4 

 ~3~ 



X 



90-8 





or v 



= 



4-96 



X 



io- £ 



,cm 3 . 

 sec. 



This gives for the volume of helium produced per year per 

 gram of radium 157 mm3 at 15°. Boltwood and Rutherfordf 

 recently found 156 mm3 at 0°. 



The volume Y of the emanation in equilibrium with one 

 gram of radium may be calculated by using in addition to the 

 above data the constants \ of the emanation, which has been 

 very accurately measured,;): and is X = 2*085 XlO" 6 (sec -1 ). 



* Royal Society Proc, A., Aug. 27, 1908. 

 fSitzungsber. Akad. Wiss., Wien, March., 1912. 



X Madame Curie, Trait e de Radioactivite, I, chap. vi. Rutherford, Sitz- 

 ungsber. Akad. Wiss., Wien, March, 1912. 



