336 RADIO-ACTIVE PROCESSES 

be nearly equal to the fraction of the radium which changes per 
year, v.e. one gram of radium should diminish in weight half a 
milligram (section 203) per year on a maximum estimate and 
1/100 of a milligram on a minimum estimate. 
If it is supposed that the 6 particles have weight, the loss of 
weight due to their expulsion is very small compared with that 
due to the emission of a particles. Taking the estimate deduced 
from the observation of Wien (section 104), that 6°6 x 10° 8 particles 
are projected per second from 1 gram of radium bromide, the loss 
of weight would only be about 1:2 x 10° gram per year. 
Except under very special experimental conditions, 1t would 
thus be very difficult to detect the loss of weight of radium due to 
the expulsion of 8 particles from its mass. There is, however, a 
possibility that radium might change in weight even though none 
of the radio-active products were allowed to escape. For example, 
if the view is taken that gravitation is the result of forces having 
their origin in the atom, it is possible that, if the atom were 
disintegrated, the weight of the parts might not be equal to that 
of the original atom. 
A large number of experiments have been made to see if 
radium preparations, kept in a sealed tube, alter in weight. With 
the small quantities of radium available to the experimenter, no 
difference of weight of radium preparations with time has yet 
been established with certainty. Heydweiller stated that he had 
observed a loss of weight of radium, and Dorn also obtained a 
sight indication of change in weight. These results have not,’ 
however, been confirmed. Forch, later, was unable to observe any 
appreciable change. 
205. Total emission of energy from the radio-element. 
It has been shown that 1 gram of radium emits energy at the 
rate of 100 gram-calories per hour or 876,000 gram-calories per 
year. If 1 gram of radium were set apart, its radio-activity and 
consequent heat emission at a time t is given by ge~™, where X is 
the constant of decay of activity of radium. Thus the total heat 
qY 
oO 
emission from 1 gram of radium is given by [ qe= aie 
/ 0 
Now on the minimum estimate of the life of radium, the value 
