﻿76 



Dr. H. L. Bronson on the Periods of 



cap P over the active wire. Fig. 2 shows the two curves 

 obtained in this way from the same active wire. E represents 



Fig. 2. 



1.204 



3 -903 



«3 



k. .602 



£ .301 





25 



50 75 



Time /n Minutes. 



100 



the a-ray activity divided by 100, and F represents the /3-ray 

 activity. From these curves it is easily seen that the ratio 

 of the /3-ray to the a-ray activity continues to decrease with the 

 time. 



Now let x be the ratio of the /3-ray ionization of radium B 

 to the a-ray ionization of radium C, and let y be the ratio of 

 the /3-ray ionization of radium C to the a-ray ionization of 

 radium C. If then we assume that the periods of radium B 

 and C are 26 and 19 minutes respectively, we obtain from 

 fig. 2 a series of equations of the following type : 



ax + by = rb, 



where a and h are the calculated percentages of radium B 

 and C remaining at any time, and r is the ratio of the total 

 /3-ray ionization to the a-ray ionization, which is calculated 

 directly from fig. 2. A number of such equations can be 

 obtained from fig. 2 by determining r at different times. 

 Each equation represents a straight line, and all should be 

 satisfied by the same values of x and y. The graphical method 

 is the simplest way of obtaining a solution. Such a solution 

 is given by the intersections of the lines in fig. 3. Tim 



