the Absorption of Rontgen Rq,i/s. 



751 



from preliminary experiments, appears slightly more absorb- 

 able than that from As. Neither has, however, been examined 

 exhaustively. 



On comparing the absorption coefficients, it is seen that i£ 

 we consider simply those absorptions which do not result in 

 the production o£ a secondary radiation characteristic of the 

 absorbing substance, the ratio of the coefficients of absorption 

 of any radiation by two elements is approximately a constant, 

 whatever be the penetrating power of the primary radiation 

 experimented upon. 



Thus if X \ A denote the coefficient of absorption of a certain 

 radiation X in a substance A, 



sAa y\\. z\i 



X X B y^-b zA- b 



approximately, provided the radiations X, Y, Z do not excite 

 the characteristic radiations in the absorbing substances A, 

 B, and 0. 



Table II. gives the ratio of the coefficient of absorption in 

 each absorbing substance to the coefficient of absorption in 

 Al for each radiation used in these experiments. The re- 

 lationship is, however, more clearly shown by the curves in 



fig. 3. 



Table II. 



Radiator. 



Absorbers. 



C 

 Al 



Mg 



Al 



Al 



Ni 



Al 



Cu 

 Al 



Zn 

 Al 



Ag 



Al 



Sn 



AT 



Pt 



Al 



An 

 Al 



Cr 



•112 

 114 

 •111 

 •111 

 109 

 •108 

 •111 

 •108 

 •164* 



•930 

 •904 



•887 

 •876 

 •866 



•881 

 •857 

 •831 

 •88 



•763 

 •747 

 •938 

 531 

 562 

 5-61 

 5-95 

 6-15 

 6-96 



•949 

 •947 

 •939 

 •953 

 1-314 

 67 

 7-29 

 7-42 

 8-80 



1-051 



1-074 

 1-052 

 1-046 

 1-111 



1-408 

 7-82 

 7-93 

 972 



1-254 

 1-271 



1-278 

 1-259 



1-277 

 1-272 



9-045 

 924 

 1084 



427 

 431 

 4-38 

 4-44 

 4-48 

 444 

 4-68 

 4-63 

 5*32 * 



5-25 

 5-33 

 5-47 

 555 

 5-70 

 5-71 

 5-84 

 5-93 

 6-60 * 



[3-8] 

 3-84 

 3-92 

 3-99 

 406 

 4-12 

 4-69 

 492 



22-6 



3-73+? 



4-14 



4-27 



Fe 



Co 



Ni 



4-28 



Cu 



4-40 



Zn 



4 5° 



As 



4-71 



Se 



529 



Act 



246 



I 













* See r 



emarks 



later. 











