1905 - 6 .] Dr Fawsitt on Electrical Measurements on Metals. 3 
of the same metal is different, then the expression for the E.M.F. 
-i 0*000198T , R 
becomes log 10 — . 
n F 2 
It is a fact that two different “ kinds ” of the same metal, when 
placed in an electrolyte, give an E.M.F. Such results as have 
been recorded are however often contradictory, and for this, I 
think, two reasons can be given. In the first place, a very thin 
layer of oxide or other substance on the surface of a metal alters 
its potential very much ; and secondly, the potential of a metal in 
contact with an acid or an electrolyte which does not contain the 
ion of the metal is a very variable quantity. 
The following cases are, however, of considerable interest. 
Rolled copper is negative as compared with soft copper, and 
hammered copper is negative as compared with rolled copper.* 
Hard steel is negative against tempered steel, f Liidtke | found 
that finely-divided precipitated silver is negative against ordinary 
silver in a solution of silver nitrate. Gallium § is liquid at a 
temperature above 30° C., but also at a temperature below this if 
undercooled: a measurement of the E.M.F. of the solid against 
liquid gallium in solution of gallium sulphate showed that the 
liquid gallium is the negative pole. The liquid condition is a 
special case (kinetic) of the amorphous phase. 
These are instances of what I believe to be a general condition, 
namely, that the potential of the metal in the amorphous phase is 
negative, and in the crystalline phase positive, when the two kinds 
of metal are placed in a solution of a salt of the metal. 
The metal I have found most suitable for experimenting upon 
is silver. With regard to the electrolyte, the most suitable is a 
solution of a silver salt, as we are here dealing with an equilibrium 
between silver and silver ion. The concentration of silver salt in 
solution does not matter at all in theory, and within certain limits 
does not matter in practice. I have used J- normal, ^-normal, and 
T^o'juormal silver nitrate solutions with identical results. When 
the electrolyte is a salt of some other metal than silver, or if the 
concentration of silver ion is very small, some silver from the 
* Wiedemann, EleMrizitat, i. 723. 
t Wiedemann, ibid., i. 738. 
+ Wied. Ann., 1893, 50, 678-695. 
§ Wiedemann, EleMrizitat, i. 739. 
