﻿Iransformation of Radium A y B, and C. 79 



A had been obtained from the early portion of the short- 

 exposure a-ray curve. The period of radium B had been 

 determined from the final portion of the long-exposure curve. 

 The period of radium C had been determined by measuring 

 the period of the product which remained after radium B had 

 been removed by volatilization.. In the calculation of the 

 «-ray curves the assumption was also made that the /3 ravs of 

 radium B gave about 2 per cent, of the total ionization pro- 

 duced by the two products B and C, when they were in 

 equilibrium. This is a slightly larger value than that found 

 in the previous experiments ; but the change in the experi- 

 mental conditions would seem to warrant the assumption. 

 In any case the total effect of this factor is very small. 



fi-Ray Decay Curves. 

 As has been stated already, the /3-ray curve is not suitable 

 for analysis, because the ratio - is not a constant, and cannot 



y 



easily be determined with accuracy. Nevertheless, it seemed 

 of interest to see in a couple of different cases how much 

 effect the ionization due to radium B had upon the /3-rav 

 decay curves. Fig. 4 shows three curves. Curve 1 was 



Fig. 4. 

 2.00 



1.70 



1.40 



1. 10 



: r^ 



25 



50 75 100 



Time in Minutes. 

 calculated on the assumption that the activity was entirely 

 due to radium C. Curve 2 was the experimental decay curve 

 obtained when the active wire was surrounded with about 

 0"047 cm. of lead. In this case the /3 rays from radium B 

 were largely absorbed. This is clearly seen from Table I., 

 where the calculated values for curve 1 were obtained by 



assuming that - =0*2. Curve 3 was the experimental curve 



obtained when the active wire was covered with about O005 cm. 



125 



