404 J. H. Reedy — Anodic Potentials of Silver. 



comprehensive way, not only the behavior of the anode poten- 

 tial during an electrolysis, but also the value of the maximum 

 potentials necessary for the separation and estimation of the 

 halogens. In no case may the anode potential rise above *521 

 volts, which has been defined as the " solution potential " of 

 silver, for at that potential silver begins to dissolve. 



The End Point in a Precipitation. — Specketer calculated 

 by means of the JS~ernst formula the maximum potential that 



Fig. 1. 





.600 





.500 





.400 



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.300 



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^< 



.200 



£ 





c 



.100 



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Q 







-.100 



-.200 







.52/ vi 



Its S 



ilution 



Poter 



itial o 



F Silv, 



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% 



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c-i- 















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M^ 















i 



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100 



1000 



10,000 



100,000 



Logarithms of Dilutions. 



Fig. 1. Influence of concentration on the deposition potentials of the 

 halogens. 



would be required for the complete separation of any halogen 

 on the assumption that the final concentration of the halogen 

 would be that of a saturated solution of the corresponding 

 silver halide. Results obtained in this way are only approxi- 

 mate, because (1) the Nernst formula (as shown in the pre- 

 ceding article) does not exactly express the relation between 

 electromotive force and concentration of the ion in the case of 

 silver electrodes ; and (2) the values of the solubilities of the 

 silver halides are more or less uncertain. 



Anodic reaction potentials of a saturated solution of a silver 

 halide on silver electrodes coated with that halide are likewise 



