Chemical Constitution of Saline Solutions. 



301 



cobalt chloride have been investigated by Potilitzin.* He failed to obtain Bersch's 

 compound CoCl2"4H20, as a distinct substance ; the changes of colour from blue 

 to red he attributed to dissociation, and pointed out that this takes place at a lower 

 temperature when the salt is in solution than when in the solid state, and it is 

 effected by such conditions as the concentration of the solution. He dissolved 

 CoCl2'6H20 in absolute alcohol, and evaporated the solution completely at a 

 temperature of 90^ to 95° C. The salt, obtained in the form of bluish crystals, had 

 the composition CoCl2'H20, as might be expected at this temperature ; but, as I 

 have already shown, evaporation at a temperature not exceeding 20° C. reproduces 

 the original hexahydrated molecule. 



A reference to the tabulated statement showing the changes in colour of saline 

 solutions when heated, &c., will make it abundantly evident that all the phenomena 

 observed, e.g. the several definite absorption spectra of the same solution at 

 different temperatures, are due to dissociation within the solution. 



* Berichte, toI. xvii., p. 276, 1884. 



[Tabulated Statement 



TEANS. EOY. DCB. SOC, N.S. VOL. VII., TART VIII. 



2 T 



