-480 The Position of Radium in the Periodic System. 

 , Fia- % 



2,5n 



7fa accorc?77iQ 

 foyfrne Cunt 



2.0 e.s J,0 3,5 *.o 



Logarithm of line-distance ( # 01 scale-division 

 = 2-8 per cent.). 



I£ x stands for the width of the line-pair, measured on the 

 scale of frequency 10 8 /^, then we have : — 





Calculated atomic 



weight =antilog. 

 (•2005 + ■ 5997 log x). 



Observed 

 atomic weight. 



Mg... 



23-84 



24-36 



Ca ... 



40-6 



40-1 



Sr ... 



87-5 



87-6 



Ba ... 



136-9 



1374 



The extrapolation for radium gives for its calculated atomic 

 weight the value 257*8. 



We do not venture to suppose that our value deserves 

 more confidence than that determined by Mine. Curie. It 

 must, however, be remarked that in view of the close re- 

 lationship of barium and radium, and the small quantities 

 with which the chemist is forced to work, the complete sepa- 

 ration of these two bodies is very difficult, and that if the 

 separation had been incomplete Mine. Curie would have 

 found too small a value for the atomic weight. According 

 to the crystallographic observations of F. Rhine, to be pub- 

 lished shortly, radium bromide and barium bromide are iso- 

 morphic, so that a joint crystallization of both substances (an 

 somorphic mixture) is, from a priori considerations, highly 



