30 
CHEMISTRY: D. P. SMITH 
Proc. N. A. S. 
The experiments about to be described were, therefore, undertaken 
in order to test this prediction in the case of palladium-hydrogen since 
the earlier observations, having been made by null methods, gave only the 
resistance for "zero current." 
Experiments. — The cathode investigated consisted of a wire of com- 
mercially pure palladium, 0.05 mm. in diameter, and approximately 110 
mm. in length. The cell and thermostat were those which have been de- 
scribed elsewhere, 3 as were also the manner of attaching and supporting 
the cathode wire, save that arrangements for observing changes of length 
nun 
Elect rojyi'ic 
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-A/VvAAAAAAAA 
A 
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Potentiometer 
FIG. 1 
Electrical connections 
were dispensed with. The electrolyte was 2-n sulphuric acid, which was 
caused to circulate during the experiment, as heretofore. The tempera- 
ture was maintained throughout at 25.00 =*= 0.02° C. 
The electrical connections are represented diagrammatically in figure 1, 
where the electrolytic circuit is shown at the left (subscripts "1") ; and 
the resistance-measuring circuit at the right (subscripts "2"). 
An experiment was conducted as follows: The switch S 2 being in 
position 1, so that the battery B 2 was short-circuited through Rz and the 
resistance-measuring circuit was open, the electrolytic circuit was closed 
by means of the plug switch Si, and was regulated with the variable re- 
sistance Ri until the millammeter Mi showed the current corresponding to 
the desired cathodic current density. Electrolysis was then continued, 
