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Values of log K at 18°. 



the metal-ions will not jet have reached their concentration of 

 saturation even in the most concentrated solutions of the corresponding 

 metal-salts. Hence, w^hen tlie corresponding metal is immerged, metal 

 ions will be dissolved, in consequence of which the solution will be 

 charged with positive and the metal with negative electricity. 



Theoretically the case, in which K would always be smaller than 

 C, can of course not occur. If log K is smaller than zero, so K 

 smaller than 1, then the theoretical possibility is given to make the 

 potential difference between the metal and the corresponding salt 

 solution reverse its sign, which reversal of sign of course takes 

 [)lace through zero. Wliether it will be possible to realize this, 

 depends on the solubility of the salt. 



If we now take the metal copper as an example, we see that for 

 this metal K has the very small value of 10 -2-^. On account of this 

 very small value of K, C is greater than K in nearly all copper- 

 salt-solutions, or in other words the concentration of the Ow-ions is 

 greater tlian the concentration of saturation. Hence copper-ions are 

 deposited on a copper bar, when it is immerged, in consequence 

 which the bar gets charged with positive, and the solution with 

 negative electricity. 



But however small K may be, it will nearly always be possible to 



^) The values of a o between parentheses have been calculated from the quan- 

 Illy of heat. 



