PROCEEDINGS 



OF 



THE ROYAL SOCIETY. 



; 'A Comparative Study of the Spectra, Densities, and Melting 

 Points of some Groups of Elements, and of the Eelation of 

 Properties to Atomic Mass." By Hugh Bamage, B.A., 

 A.E.C.Sc.L, St. John's College, Cambridge. Communicated 

 by Professor Gr. D. Liveing, P.E.S. Beceived November 7, — 

 Bead November 28, 1901. 



[Plates 1, 2.] 

 Introduction. 



This investigation was begun in the hope that it would lead to the 

 discovery of some of the laws which determine the distribution of lines 

 and bands in spectra : those laws, more especially, which govern the 

 changes of oscillation frequency of corresponding lines in the spectra 

 of some of the metals. 



A. Mitscherlich appears to have been the first to make a compara- 

 tive study of spectra.* He compared the spectra of the haloid salts of 

 the metals of the alkaline earths. He found that individual lines recur 

 in the spectra of one and the same metal, which, according to the 

 halogens, are more or less distant from one another. Fluorides form 

 an exception. In the spectra of barium compounds the distances (on 

 the scale of his spectroscope) between two prominent lines in the 

 various spectra were to each other as the " atomic weights " of the 

 compounds. In barium chloride the distance between the two lines 

 was 3 - 9 scale divisions. If x is the difference between the two corre- 

 sponding lines in the spectrum of barium iodide, then : — 



3-9 _ 104 _ EaCl 2 

 x ~ 195-5 ~ Bal 2 ' 



Mitscherlich determined a common starting point for the haloid 

 salts of barium, and extended the work to the spectra of compounds of 

 calcium and strontium. 



* 'Pogg. Ann.,' vol. 121, pp. 459—488, 1864; 'Phil. Mag.,' vol. 28, p. 169, 

 1864. 



VOL. LXX. B 



