1892.J Voltaic Cells with Fused Electrolytes. 



Zinc | ZnCl 2 | Ag 2 Cl 2 | Silver. 



85 



Zinc | ZnCl 2 | CuCl 2 | Copper, 



Except in the zinc-silver cell, and to a minnte extent in the zinc- 

 tin cell, there is no evidence of polarisation by reversal. The other 

 two cells show the remarkable property of possessing a greater 

 electromotive force after short circuiting than before it ; and since 

 this recurs repeatedly in the observations on both cells, it would 

 seem to be more than accidental. 



II. Cells with Double Chlorides. 



As I have already stated, the present investigation was suggested 

 by the behaviour of magnesium and aluminium in aqueous electro- 

 lytes ; and as a matter of fact these metals were experimented on in 

 the more complicated cells described below before the simpler cells of 

 Table I were tried. Owing to the high fusing point of magnesium 

 chloride, and the volatility of the aluminium compound, it was incon- 

 venient to work with these chlorides in the fused state ; and this 

 difficulty had to be surmounted by employing the double chlorides of 

 magnesium and potassium, and of aluminium and sodium. A similar 

 method was adopted with ferrous chloride, which is infusible by 

 itself. 



It may be objected that this method introduces a solvent, the very 

 complication which it is desired to avoid, since potassium chloride 

 may be looked upon as the solvent of the other chlorides. But in 

 comparing fused potassium chloride with water as a solvent of 

 chlorides, there are two important differences, (i) With potassium 

 chloride, the anion is the same as that of the dissolved substance, 

 while with water it is not. (ii) The heat of combination K, Cl is 

 greater than that of any of the other chlorides X, Cl dissolved 

 in it in these experiments ; therefore the metal X when immersed 



