1880.] On the Absorption Spectra of Cobalt Salts. 



53 



further change takes place. With other liquids which dissolve the 

 •cobalt salt freely, a similar series of changes occur, but if liquids in 

 which the chloride is much less soluble be used, then according to their 

 solvent power only the first (or most dilute stage), or the first and 

 second stage, is obtainable ; for instance, if dry ether is used as the 

 solvent, it yields only a spectrum corresponding to the first stage. 

 With anhydrous acetic acid, in which the cobalt chloride is more freely 

 soluble, both the first and second stage are obtainable. If the dry 

 chloride in fine powder be shaken up with a liquid in which it is inso- 

 luble, such as carbon tetrachloride, then only a spectrum similar to 

 that of the fused chloride is visible. 



The anhydrous cobalt chloride dissolved in water gives a pink solu- 

 tion. This solution, when it contains as little as 0*1 grm., or as much 

 as 25 grms., of the salt in 100 cub. centims. of water, gives only a 

 wide absorption-band, shading off on both sides, and whether a short 

 column of the strong solution or a correspondingly long column of 

 -the dilute solution be examined, identical spectra are obtained, so that 

 within these limits the same compound appears to exist in the solution. 

 If, however, the solution approaches saturation (100 cub. centims. of 

 water can dissolve at 16° 32 grms. of the cobalt chloride), then another 

 spectrum is visible, and this is again the spectrum of the dissolved 

 ■chloride : the same spectrum as is obtained either by dissolving 

 cobalt chloride in fused potassium chloride, or in alcohol, or in 

 hydrochloric acid, thus apparently the anhydrous chloride exists in 

 an aqueous solution. The action of heat, and the action of bodies 

 capable of combining with water, in aqueous solutions of cobalt 

 chloride, are identical, both tending to destroy the broad absorption 

 band of the hydrate, and to form the banded spectrum of the dissolved 

 anhydrous chloride. 



The very characteristic spectrum of the oxide of cobalt is well known. 

 The precipitate obtained by the addition of potash or soda in excess to 

 any cobaltous salt, shows well this spectrum. If ammonia be the pre- 

 cipitant, a somewhat simpler spectrum is obtained. Vogel has already 

 pointed out the similarity of the spectrum of a piece of cobalt glass 

 and this oxide spectrum. The glass spectrum is apparently similar 

 to the spectrum formed by the precipitate with potash and soda, 

 probably then the extra band visible in these cases and not when 

 ammonia is used, is due to a compound of the alkali and cobalt. The 

 bearing of these spectra on Winkler's supposed cobaltate of potash is 

 then discussed. Further, it is shown that if the above precipitation 

 of oxide be made in solutions in which the cobalt salt is in excess, or 

 .even if precipitated oxide be warmed or shaken up in the cold with a 

 solution of cobalt chloride, a new compound is formed, an oxychloride 

 which gives a different spectrum ; its formation and its decomposition 

 by water is well traced in the varying spectra producible from it, and 



vol. sxxi. F 



