﻿Ranges of the a Particles from Uranium. 



443 



Three typical curves are given in fig. 2, the ionization 

 being plotted against the range of the a particles. Corrections 



Fio-. 2. 



Uranium' 1 



Ionium 



Polonium 





ir 



I Z 3 I 2 3 1 2 3 4 



Range of ol particles in cms. 



were made for the natural leak and also for the effect due to 

 the uranium in the case of the ionium and polonium films. 

 All three curves are typical of the ionization curve due to a 

 parallel pencil of a particles in hydrogen. But while the 

 curves for ionium and polonium completely agree with each 

 other, the curve for Uranium is distinctly different. In the 

 latter case the maximum is not so sharply defined and the 

 curve shows a much slower fall from the maximum towards 

 the end of the range-. To make this clear, the curve for 

 ionium (see dotted line) is superposed on that of uranium, 

 the ends of the two curves beino- made to coincide. The same 

 difference between the curves was also brought out when the 

 ionization was measured in hydrogen at a higher pressure or in 

 air, or when slightly thicker films were used. As has already 

 been pointed out, this cannot be due to the thickness of the 

 film or to any other experimental cause. 



Jt seems> therefore, necessary to conclude that there exist 

 two a-ray products in uranium which possess a slight 

 difference of range. A determination of the difference of 

 range of the two products could be made by comparison with 

 a theoretical curve obtained by adding together two simple 

 ionization curves of known difference of range. In this way 

 it was found that by compounding two ionium or two polonium 

 curves which were shifted relative to each other by 1 mm.. 



