BANCROFT. POTENTIAL OF METALS. 



107 



vestigators, as given in Table VIII., show the same thing, though not 

 quite so clearly. The values for ZniCu in solutions of chlorides, bro- 

 mides, and iodides are found to be identical by Paschen, by Overbeck 

 and Edler and by Regnault, though the three sets differ hopelessly in 

 absolute value. Braun makes the bromides and iodides the same, and 

 puts the chlorides, sulphates, and nitrates in a group together. There 

 is not the same agreement among the reversible cells in which Pb 

 forms one of the electrodes ; but this is due in part to the insolubility 

 of the lead salts. With the polarizable cells things are much clearer, 

 though the discrepancies between the values found by different ob- 

 servers complicates matters very much. Ostwald finds practically the 

 same value for ZulPb in all solutions except acetates. Paschen makes 

 the bromides and sulphates the same, while Overbeck and Edler find 

 the chlorides and iodides identical. On the whole, we may say that 

 the theory of Nernst has predicted the facts with great accuracy so far. 

 If, however, the single-liquid cells are the limiting cases of the two- 

 liquid reversible cells, and if log P is a function of the electrodes and 

 temperature only, the electromotive force should always be indepen- 

 dent of the nature of the negative ion of the salt solution. That this is 

 not so will be seen from Table IX, 



Tx\BLE IX. 



