On the Atomic Weight of Radiiun, 05 



Taking the atomic weights of calcium and strontium on 

 the oxygen scale as 40*1 and 87*6, we may then calculate 

 the atomic weight o£ barium on the assumption that the 

 [ioints assumed to correspond in the three spectra have some 

 physical connexion, and that they do actually lie upon straight 

 lines. We thus get by calculation for the atomic weight of 

 barium 



From {a) 136-90 



(6) 136-97 



(c) 137-51 



{d) 138-06 



(e) 137-85 



Mean 137-46 



the accepted value being 137*4 



It would seem that similar relationships hold, to a certain 

 extent, between the spectrum of radium and the spectra of 

 mercury, barium, and calcium, and in the present communi- 

 cation I have made an attempt to calculate the atomic weight 

 of radium from these relationships. They seem to me too 

 remarkable to be attributed to chance. Both kinds of rela- 

 tionship seem to exist. 



The brightest lines in the spectrum of radium are 20714*8 of 

 intensity (10), 21350*9 (14;, and 26207*7 (16). There are two 

 lines in the barium spectrum, 35892*6 (8r), and 36070*2 (6), 

 which seem to correspond to the first two radium lines, and 

 to a calcium line at 43930*4 (8r). There does not appear to 

 be a second calcium line at this place, but it is situated in 

 the extreme violet, and it is quite possible that a second line 

 may have escaped observation. 



Taking the calcium line to correspond to the less refrangible 

 barium and radium lines, by calculating from the atomic 

 weights Ba = 137*4 and Ca = 40*l, we g^i '2m?,2 for the 

 atomic weight of radiunic 



The radium line 26207'7 lies on a straight line with 

 mercury 31982*2 (lOr), and barium 42807*0 (8r). Calcu- 

 lating from Hg = 200 and Ba = 137*4 we get 226*42 for the 

 atomic weight of radium. 



Other correspondences of the like kind seem to be 



Eadium. Mercury. Barium. Calcium, 



(a) 17195-5 22362-/' (5) 32545-2 (6>-) — 



(6) 22052-7 27386-6 (lOr) 37845-2 (4) — 



ie) 21149-7 . . 36987-4 (4;-) 45423-0 (8r) 



Tliese give 225-21 from («) Mercury and Barium, 



225*32 from (b) „ „ and 



226-52 from (c) Barium and Calcium, 



The connecting lines in these five cases are very nearly 

 Phil Mag. S. 6. Vol. 6. No. 31. July 1903. F 



