486 



On the Absorption of X-Rays. 



From the different values of X. a. k. I have tried to' 

 ascertain for different elements, there is evidence for 

 believing that there exists a simple relation between the 

 above-named quantity for a certain element and the atomic 

 weight or atomic number. According to Bragg and Pierce, 

 the atomic absorption coefficient is thought proportional to the 

 fourth power of the atomic number (3), but after the results 

 brought out by my experiments this cannot hold. Since 

 Bragg and Pierce have only tested a few elements, the lack 

 of agreement in this respect between their results and mine 

 will be easily explicable. 



Fig. 2. 



"720 



680 

 640 

 600 

 S60 

 E20 

 480 

 440 

 400 



360 



X.af.k. 



320 

 2 SO 

 240 

 200 



\eo 



120 



80 

 40 



te~& 



#3 



Jr.* 





l<r 





# 



-■:: 



■ Fb 



Q 



£4 32 40 40 56 64 72 60 83 

 Atomic number. 



The connexion between X.a. k. and the atomic number is 

 graphically brought out in fig. 2, where the atomic number 

 put as abscissa and the corresponding value X.a.k. (Table VI.) 

 as ordinate. The curve displays the values of X. a. k., arranged 



