Chemical Constitution of Saline Solutions. 301 
cobalt chloride have been investigated by Potilitzin.* He failed to obtain Bersch’s 
compound CoCl,'4H,0, 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 
CoCl,6H,O 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 CoCl,,H,0, 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, vol. xvii., p. 276, 1884. 
[TasuLateD STaTEMENT 
TRANS. ROY. DUB. SOC., N.S. VOL. VIJ., PART VIII. 2T 
