[ 53 ] 



VI. Some Observations on the Absorption Spectra of the 

 Vapours of Inorganic Salts. By E. J. Evans, B.Sc, 

 A.R.C.S., Lecturer hi Physics, Victoria University, 

 Manchester *. 



[Plate II.] 



Introduction. 



SOME time ago the present authorf published investiga- 

 tions on the absorption spectra of the vapours of iodine, 

 bromine, selenium, and tellurium at various temperatures, 

 and later, as a continuation of the above investigations, the 

 absorption spectra of the vapours of certain simple salts were 

 examined. This research was not completed, as the author's 

 attention was diverted to other problems, and the object of 

 the present paper is to give* a brief account of the results 

 then obtained. 



It is well known that the absorption spectra of the above- 

 mentioned elementary substances show the presence of well- 

 defined absorption bands, and it was considered of some 

 interest to determine whether the absorption spectra of the 

 vapours of a few inorganic salts show the presence of similar 

 ba?ids. For this purpose the absorption spectra of the 

 chlorides of ammonium and mercury, and the chloride, 

 bromide, and iodide of cadmium were examined. It was 

 found that all the vapours examined, with the possible 

 exception of ammonium chloride, showed evidence of a 

 general selective absorption in the ultra-violet, and in no 

 case could it be definitely proved that the vapours of the 

 salts gave any well-defined absorption bands similar to those 

 of CI, Br, and I. 



These conclusions refer to the particular region of the 

 spectrum (X 2500-X. 6700) which was investigated. No 

 measurements of the variation of the general absorption with 

 wave-length were made. 



Experimental Arrangement. 



A weighed quantity of the salt under investigation was 

 placed in a quartz tube, which was evacuated to a low 

 pressure through a side-tube connected to a mercury pump. 

 The side-tube was then sealed off in the oxy-hydrogen flame. 

 The quartz tube was afterwards placed at the centre of an 



* Communicated by Sir E. Rutherford. This paper formed a portion 

 of a thesis approved for the D.Sc. degree by the University of London. 



t Astrophys. Journal, xxxii. pp. 1-16 (1910^ ; xxxii. pp. 291-299 

 (1910) ; xxxiv. pp. 277-287 (1911) ; xxxvi. pp. 228-238 (1912;. 



