258 



Dr. W. J. Russell. 



Trouyet (Charles) Pronostic Sericole du 15 Mars, 1880, pour la 

 Syrie. 8vo. Beyrouth (Syrie) 1880. The Author. 



Wolf (H.) Geologische Gruben-Revier-Karte des Kohlenbeckens von 

 Teplitz-Dux-Briix im Nordwestlichen Bohmen. Folio. Wien 

 1880. Begleitworte. 8vo. Wien 1880. The Author. 



" On the Absorption Spectra of Cobalt Salts." By William J. 

 Russell, Ph.D., F.R.S., Treas. C.S., Lecturer on Chemistry 

 at the Medical School, St. Bartholomew's Hospital. Re- 

 ceived August 4. Read November 18, 1880. 



The following investigation was commenced at the suggestion, and 

 indeed in conjunction with, Mr. Lockyer. Other work, however, pre- 

 vented his continuing with me this research, but I am much indebted 

 to him not only for instruction in methods of spectroscopic observa- 

 tion, but also for important suggestions and much aid in the course of 

 the work. 



The more immediate object of the investigation was to examine 

 carefully and systematically the absorption spectra produced by certain 

 coloured liquids and solids, in order to identify the spectra with the 

 substances producing them. If this be fully done, a powerful means 

 has been obtained for investigating the changes, be they either 

 chemical or physical, which occur more especially in cases of solution. 

 Of all coloured substances the cobalt salts seemed most suitable for 

 commencing the investigation with, as they give well marked band 

 spectra, and are salts well known and easily obtained. 



The following observations were made with a Dasaga's spectroscope 

 having a single heavy glass prism, and, as a rule, it did not seem 

 advisable to use higher dispersive power. The positions of the bands 

 are given in wave-lengths of millionths of a metre, obtained from the 

 observations by graphical interpolation. 



Cobalt chloride was the salt first examined ; the absorption spectra 

 produced by it when pure and dry were carefully ascertained, and then 

 the changes occurring in the spectrum when it was acted on by water 

 and by other substances. First, with regard to the pure cobalt chlo- 

 ride (CoClo). A specimen of the pure salt was fused out of contact 

 with the air in a glass tube. Another specimen of this salt was 

 obtained by dissolving pure cobalt in hydrochloric acid, fusing it in 

 an atmosphere of that gas, and sealing it up in a glass tube to exclude 

 moisture. Pig. 1 represents the absorption spectrum which was 

 obtained in both cases. When in place of pure the commercial salt 

 was used, when the salt was formed by the action of chlorine on the 

 metal, when the ordinary hydrated cobalt chloride was dried and fused 



