RADIUM. 201 



of distribution, iilwa3'.s be a few atoms in the gas possessing this 

 amount of kinetic energy; these would by hypothesis break up. If in 

 doing so they gave out a large amount of energy in the form of 

 Becquerel radiation, the gas would be radio-active and would continue 

 to be so until all its atoms had passed through the phase in Avhich they 

 possessed enough energy to make them unstable. If this energy were 

 100 times the average energy it would probably take hundreds of 

 thousands of years before the radio-activity of the gas was sensibl}^ 

 diminished. Now in the case of radium, just as in the gas, the atoms 

 arc not all in identical })hysical circumstances, and if there is any law 

 of distribution like the Maxwell-Boltzmann law, tliere will on the 

 above hjq^othesis, be a very slow transformation of the atoms accom- 

 panied by a liberation of energy. In the hypothetical case we have 

 taken the possession of a certain amount of kinetic energy as the 

 criterion for instability. The argument will apply if any other test is 

 taken. 



It may be objected to this explanation that if the rate at which the 

 atoms are being transformed is very slow, the energy liberated by the 

 transformation of a given number of atoms must be very much greater 

 than that set free when the same number of atoms are concerned in 

 any known chemical combination. It must be remembered, however, 

 that the changes contemplated on this hypothesis are of a different 

 kind from those occurring in ordinary chemical combination. The 

 changes we are considering are changes in the contiguration of the 

 atom, and it is possible that changes of this kind may l)e acc()nn)anied 

 I)}' tlic liberation of very lai'ge quantities of energy. Thus, taking 

 the atomic weight of radium as 225, if the mass of the atom of radium 

 were due to the presence in it of a large number of corpuscles, each 

 carrying the charge of 3.4 by lO""^*^ electrostatic units of negative 

 electricity, and if this charge of negative electricity were associated 

 with an ecjual charge of positive, so as to make the atom electricall}' 

 neutral, then if these positive and negative charges were separated by 

 a distance of 10"*^ cm., the intrinsic energy possessed by the atom 

 would l)e so great that a diminution of it by 1 per cent wcudd be able 

 to maintain the radiation from radium as measured by Curie for 

 30,000 years. 



Another ])oint to b(5 noted is that the radiation from a concentrated 

 mass of radium may possibly be very much greater than that from 

 the same mass when disseminated through a large volume of pitch- 

 blende; for it is possible that the radiation from one atom may tend to 

 put the surrounding atoms in the unstable state. If this were so, more 

 atoms would in a given time pass from the one state to the other if 

 they were placed so as to receive the radiation from their neighbors 

 than if they were disseminated through a matrix which shielded each 

 radium atom from the radiation given out by its neighbors. 



