274 Prof. Potter. Electrical Effects accompanying the [July 14, 



produced no effect. When, however, these electrodes were connected directly 

 with the galvanometer the spot immediately moved " off scale," showing the 

 existence of an electric current developed in the cell, the strength of which 

 depended upon the resistance of the circuit. 



III. Platinum in the jar, non-polarisable electrode in the porous pot. An 

 E.M.F. was developed of much the same voltage as in I, as shown by a 

 comparison of the curves in fig. 6. 



IV. Non-polarisable electrode in the jar and platinum in the porous pot. 

 No E.M.F. could be detected with the condenser, but an electric current was 

 •evident as in II. 



It should be remarked that the relative charge upon the electrodes in the 

 ■cases III and IV was, relatively speaking, large ; thus in III the number of 

 deflections showed a difference of potential of 1 volt, and also in IV a 

 difference of potential of 1"1 volt. The deflections on the scale of the 

 galvanometer were of opposite sign, that in III being anti-zincative, and that 

 in IV zincative. In III the voltage due to the relative charge decreased as 

 the zinc was acted upon by the sulphuric acid, at first very rapidly, until the 

 maximum E.M.F. was produced by the zinc and sulphuric acid. Following 

 this it increased gradually as the action ceased ; and after some 12 hours, 

 when all the zinc had been dissolved, the relative charge showed only a 

 slight difference from its former voltage. In this case the E.M.F. produced 

 by the solution of the zinc was opposite in sign to the relative charge of the 

 pair of electrodes. 



In IV the relative charge remained constant throughout the duration of 

 the experiment. 



A cell charged with yeast and glucose and a similar four pairs of electrodes 

 gave results exactly parallel with those described for zinc and sulphuric 

 •acid : — 



I. Platinum electrodes. The curve of the E.M.F. with galvanometer and 

 condenser developed in the normal manner. 



II. Non-polarisable electrodes. No deflections of the galvanometer were 

 to be observed when the condenser was discharged through it, but a very 

 •distinct current was registered when the electrodes were connected directly 

 with the galvanometer. 



III. This gave the normal curve of the E.M.F. as in I. 



IV. The same effects as in II were indicated. 



All these tests combine to show quite clearly that, though a current is 

 certainly generated, no voltage can be registered with non-polarisable 

 electrodes, and this special form of electrode is unsuitable for use with the 

 condenser. 



