280 W. Hallock—Smee Battery and Galvanic Polarization. 
platinum, and from results here obtained it would seem to be 
true for at least carbon also, that an electromotive force which 
is theoretically too weak to decompose the solution between the 
platinum electrodes still does generate a current through a vol- 
tameter, which was originally free from all dissolved gases, and 
polarizes the electrodes, assisted by the occlusion of the evolved 
gases by the platinum. 
It is difficult to explain according to the “ chemical theory” 
why, on closing the primary circuit, the polarization does not 
immediately reach its maximum value instead of doing so grad- 
ually, as is the case. According to the “contact theory” the 
polarization of H,SO, between platinum electrodes, on closing 
the primary current, increases gradually until we have a plati- 
num kathode saturated with hydrogen opposed to the anode 
saturated with oxygen, just as in the polarization of ZnSO, it 
increases until we have the kathode covered with zinc, oppose 
the Pt | O anode, in other words, until our voltameter has 
become a Smee cell. 
Pt | H+H | HCl+HC!| C1+C1 | Pt. (1) 
and in the other case 
Pt | H+H | NaOH +NaOH | NaCl+NaCl | Cl+Cl| Pt. (2) 
That these two series should not give the same electromotive 
force is what one would expect.* A test experiment, however, 
gave the following equation, 
Pt | NaOH+Na0OH | NaCl+NaCl | Pt=0°39 D. 
and furthermore it gave no difference in the polarization when 
the kathode as well as the anode was surrounded with NaCl 
solution, and when the vessel containing the kathode was filled 
with NaOH solution, thus showing that series (2) really repre 
sents the forces acting in the polarization of NaCl solution 
between platinum electrodes. : 
The secondary reactions in some cases must be very peculiar ; 
for example in the electrolysis of a solution of MnCl, there was 
no chlorine gas evolved, and the anode became covered with @ 
.O, H,SO, or dilute HCl, but 
concentrated HCl dissolved it off to a reddish-brown solutie® 
which gave off quantities of free chlorine. The chlorine ha 
* Aryton and Perry, Trans. Roy. Soc., i, p. 34, 1880; Helmholtz, Wied. eo 
iii, p. 201, 1878; F. Moser, ibid., p. 216; and KE, Kittler, Wied. Ann., x1, P- ©" * 
1881. 
