on 



the International Standard. 325 



expelled a particles from the three products, emanation, 

 radium A and radium C respectively, then the energy per 

 atom released during the transformation of one atom is 



E x + A for emanation, E 2 + A for radium A, s for radium 



A 



B, E 3 4- ^- for radium C, since the latter expels both an a 



and /3 particle, and thus its nucleus charge is finally lowered 

 by one unit. 



The resultant energy due to a transformation of one atom 

 of all of these substances is E 1 + E 2 + E 3 f 2 A, and the ratio 

 of the energy liberated from radium B and radium G together 

 to the total is 



E 2 + E 2 + E 3 +2A t 1 ' 



In this calculation, no account is taken of the energy ex- 

 pelled in the form of primary /3 rays and y rays, but only of 

 the energy from the a rays and from the electronic distri- 

 bution. 



If the above point of view is correct, the ratio of the 

 heating effect of radium B and radium C together (sub- 

 tracting the energy due to ft and y rays from these products), 

 should be less than the value calculated from the energy of 

 the u particles. Now this point was carefully examined by 

 Mr. Robinson and myself (loc. tit.) some years ago, and we 

 drew attention to the fact that the heating effect of radium 

 C was distinctly less, compared with that due to the emana- 

 tion and radium A, than the theoretical ratio calculated from 

 the energy of the expelled « particles. 



It was found that the observed heating effect due to 

 radium (B + C) together in equilibrium with one curie of 

 emanation was actually in very nearly the theoretical ratio 

 with the calculated heating effect due to the emanation and 

 its products, viz. *403. Of the observed heating effect, 

 however, 43 gr. cals. out of a total of 103*5 per curie of 

 emanation per hour were to be ascribed to the absorption of 

 part of the ft and y rays emitted by radium B and radium C. 



From these data, the value of A (equation 1) can be 

 deduced, and is found to be about 3*2 gr. cals. per hour 

 corresponding to one curie of emanation. The heatiug effect 

 due to the a rays alone should be consequently 6*4 gr. cals. 

 less than the observed value 99*2, that is 92*8. The actual 

 calculated heating effect comes out 92*4, assuming nE = 

 11*1 xlO" 10 e. m. units. "When this additional factor is 

 taken into account, the observed heating effect is thus in 



