176 PHYSICAL SCIENCE 



the solid as in the solution, that it escapes from 

 the solution as fast as it is formed, and that it does 

 not appreciably escape from the solid at all, it is 

 clearly possible to calculate the amount of emana- 

 tion that should be stored in the solid, as compared 

 with the amount produced and emitted by the 

 solution in a given time. 



The calculation shows that 463,000 times more 

 should be stored in the solid than is emitted by 

 the solution in one second. Now if, as supposed, 

 the emanation is stored in the solid, this large 

 amount will be liberated instantaneously when that 

 solid is dissolved in water. Rutherford and Soddy 

 measured this rush of emanation by its effect on an 

 electroscope, and found that it was 477,000 times 

 greater than the quantity afterwards developed 

 by the solution in one second : a remarkable 

 confirmation of the several hypotheses given 

 above. 



The effect of raising the temperature is similar 

 to that of solution. When a solid radium com- 

 pound is brought to a red heat, a rush of emana- 

 tion takes place, which makes the initial emanating 

 power some hundred thousand times greater than 

 that of the cold solid. This high rate of emission, 

 however, does not last ; it, also, is due to the 

 rapid escape of stored material. 



By experiments such as these, the emanating 

 power of radio-active elements has been brought 

 into line with their other radio-active properties, 

 and has been shown to depend only on the mass 

 of the element present, whatever be the state of 

 combination in which that element exists, and 

 whatever be the physical conditions under which 

 the process occurs. 



