1496 
must have the greatest solubility product. Now the concentration of 
the metal ions and -electrons can certainly not be greater in a 
solution than in the pure metal, when this is totally ionized. The 
atomic weight of Li=?7, and the sp.gr. about 0.6. Hence 1 litre 
of metallic 2 weighs about 500 gr. and contains not quite 100 
eramatoms Zi. Hence the concentration of the Zi-ions cannot be 
greater than 100. The solubility product of Li can, therefore, as 
(Li) = (8), not be greater than 10°. 
This value, which is certainly much too large, only indicates a 
maximum value. The solubility product will therefore also be 
smaller than this value, because the concentrations of the ions and 
electrons are smaller in the coexisting solution than in the metal. 
By the aid of it we can indicate an upper value for all other 
metals. For hydrogen we find e.g., Ar: —Ay, being = — 3.0: 
bys 
for silver, for which Az; — A4, = — 3.8 becomes Lag ZAO 
It appears therefore from this that the solubility products of most 
metals have very small values. Even for a metal so strongly negative 
as Na Ly, must be < 10‘. 
Now it appears also from these values that a direct determination 
of the solubility products is impossible. 
As a metal that decomposes water, with formation of hydrogen 
is more negative than hydrogen and Ly,<10~**, only those metals 
are not attacked by water for which L3,< 10°“, a value which 
is still much smaller than that of the least soluble salts. 
6. Polarisation and Passivity. 
We shall now examine if it is possible that a metal in which in 
case of unary behaviour the ionisation equilibrium 
M2M +6 
exists, will allow of polarisation, resp. passivation. For this purpose 
we consider the equations (17«) and (18a) 
RT  K'w(s) 
N= In — a NE te 
F n UD) (1 fa) 
RAE Ke (Gc 
and A=—In Kog een beek ord others alsa) 
I (47) 
From these relations follows: 
BT KOs) RT, (Mi) 
— Na == - 
F (AL) fF K'yr(M 8) 
