394 Dr. J, L. Grlasson on 



The values of the atomic coefficients are shown in the last 

 two columns of Table I., and their values plotted logarith- 

 mically against atomic numbers are shown in fig. 1. 



Table I. 



Symbol. 



At. Wt. 

 A. 



Density 

 D. 



At. No. 

 N. 



Schmidt's values. 



Atomic coefficients. 



















a 







a 



i b 



Mg ... 



24-4 



1-74 



.12 



6-30 



576 



89 



81 



Al ... 

 Fe ... 



27-1 



55-9 



2-65 



13 



8-65 



9-63 



89 



99 



7-8 



26 



24-0 



55-9 



172 



400 



Co ... 



59-0 



8-5 



27 



25-7 



60-0 



178 



417 



Ni ... 



58-7 



8-9 



28 



26-1 



70-5 



172 



465 



Cu ... 



63-6 



8-93 



29 



27-0 



700 



192 



496 



Zn ... 



65-4 



719 



30 



21-6 



56-9 



196 



518 



Pel ... 



107 



11-9 



46 



30-0 



160 



268 



1432 



Ag ... 



108 



10-5 



47 



26-0 



144 



268 



1480 



Sn ... 

 Pt ... 



119 



7-3 



50 



l 



15-6 



100 



260 



1630 



195 



21-5 



78 



41-0 



468 



372 



4240 



An ... 



197 



19-3 



79 



362 



480 



368 



4910 



Pb ... 



207 



11-4 



82 



19-3 



266 



350 



4820 



Bi 



208 



9-8 



83 



163 



254 



348 



5400 



3. The atomic absorption coefficient. — The figures in 

 the penultimate column of the table do not increase regularly 

 as one proceeds to elements of higher atomic number, but 

 tend to group themselves about four different values, being 

 approximately constant for elements in the same period of 

 the periodic table. This is shown graphically in fig. 1, 

 curve A. Unfortunately the elements used by Schmidt are 

 not well enough distributed to give a complete idea of the 

 shape of the curve ; by analogy with other periodic curves 

 we may expect the missing elements to show intermediate 

 maxima. But it is a remarkable fact that the values for 

 these four groups are almost exactly in the ratio 1:2:3:4. 

 This may be merely coincidence, but in any case it seems to 

 be a consequence of Schmidt's work, that the atomic absorp- 

 tion coefficient is dependent chiefly on tlie arrangement of 

 the electrons in the atom and not so much on their total 

 number. In view of the importance this result would 

 possess if it could be definitely established, it is highly 

 desirable that Schmidt's results should be confirmed and 

 extended, if possible by an experimental method which does 

 not involve so many theoretical assumptions. 



It is obviously possible to draw a straight line through 

 the points of curve A which fits fairly well, and this is in 



