288 



Mr. William Sutherland on the 

 Table XXXYIII. 





Li. 



Na. 



R. 



§Mg. JCa. £Sr. £Ba. fZn. 1 iCd. 



Dynic equivalent 



Refract ion-equivalent . 



•5 

 •5 



•8 

 •63 



1-6 



1-06 



1 

 •3 -55 -9 1-7 -65 ' 1-22 



•46 ' -68 -90 1-01 -67 9 



1 





Ag. 



P>b. 



iCxx. 



|Mn. 



|Pe. 



iNi. 



$Co. J.AL 



|Fe. 



Dynic equivalent 2*70 ! 2"0 



Refraction-equivalent. 2'06 T63 



•6 

 •76 



•5 



•8 



•6 



•81 



•7 



•69 



•8 

 •71 



•2 



•37 



•8 



•93 



l 





hOr. 



01. 



Br. 



I. 



NO a . 



ISO,. 



i0O 3 . 



|Cr0 4 . 



Dynic equivalent 



Refraction-equivalent . 



•3 

 "7 



1-4 

 1-4 



2-7 

 2-2 



3-8 

 3-6 



2-3 

 1-8 



1-35 

 11 



•5 



•8 



2-4 



Again we see a remarkable parallelism between the dynic 

 and refraction-equivalents of the elements and radicals. Of 

 course there are refinements which will yet have to be made 

 in the calculation of the dynic equivalents, but it is not likely 

 that they will make the parallelism seriously closer. 



17. Meaning of the Parallelism hetiveen Dynic and Refraction 

 Equivalents, and general speculations as to the volumes of the 

 atoms and their relation to ionic speeds. — We are now called 

 upon to consider the meaning of this parallelism which has 

 been demonstrated both for organic and inorganic compounds, 

 and we shall be helped thereto by the very simple theory which 

 I have given of the Gladstone refraction-equivalent (Phil. Mag. 

 Feb. 1889), showing that to a first approximation 



(n-l)ii-= 2(IT-1)U, 



where n is the index of refraction and u the molecular domain 

 of a substance, N the index of the matter of an atom, and U 

 its volume in the molecule. Hence the refraction-equivalent 

 of an element is the product of the refractivity (Sir W. Thom- 

 son's name for index minus unity) of the substance of its atom 

 and the volume of the atom (the volume of the atom being 

 measured in terms of the unit in which the molecular domain, 

 usually called molecular volume, is measured); so that the re- 



