Decay of emf Between SS316 Electrodes in KOH Solution
Shweta Ganguly*, Jyoti Agarwal* & Abhra Shau**
*3rd Semester (B.Tech ), **Research Scholar
Chemical Engineering, Universuty of Calcutta
Abstract
Shau (personal communication) reported the generation of emf between two SS316 electrode immersed in KOH solution . It is seem to be
unexpected to get an emf between same material in a solution. Investigation is being carried out in the laboratory.
Introduction
Shau while working on electrolysis of water using SS316 electrodes, reported the formation of thin scales/ deposits on the surface
of the electrode material as shown in Fig. 1. He also found an emf to develop between the two electrodes, when both are placed in
the same solution with initial value of 863.2 mV. The emf decayed over a period of 56 hrs and became steady at 0.11 mV. The
experimental setup used by Shau is shown in Fig. 2 and the decay of emf in Fig. 3.
0.9
1.0
0.7
Potential difference, mV
Potential difference, V
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0.1
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0.0
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Time, sec
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Time, sec
Figure 1: Packing materials of
elcctrode before & after
electrolysis.
Figure 2: Experimental set-up used by
Shau.
Figure 3.a: Decaying of Potential
difference for first 10 hrs.
Figure 3.b: Decaying of Potential
difference after 10 hrs until steady state
reached.
Objective
Normally, one would not expect an emf to be generated between the electrodes of same material and geometry placed in the same
solution. Thus the objective of our work was to verify whether such an emf is produced, and if so, try to find out an explanation
for the origin of this emf.
Potential difference between electrodes, mV
Figure 4: Experimental set-up.
40
30
20
10
0
-10
0
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Experimentation
Experimental setup is a simple electrolytic cell as
shown in Fig. 4 with two flat plate electrodes of same
material (SS316). The area of the electrodes (portion
immersed in solution) was 10cm2. The area could be
adjusted by a suitable threaded bolt and nut
arrangement. In the current study, though, the electrode
area was not changed. Distance between the electrodes
was 1 inch. The electrolyte i.e. KOH solution of
concentration of 0.50 wt%, was made by dissolving
KOH pellets (with assay ≥ 84%) in double distilled
water. The potential difference between the electrodes
was measured by a 4 & half digit digital voltmeter of
range 0.01 to 1000 V and the experimental data were
obtained as illustrated in Fig. 5.
1200000
Time, Sec
Result and Discussions
i. An emf is produced though it does not seem to be repeatable.
ii. Figure 6 depicted that the change in emf measure with room electrical
appliances on & off it may be inferred that switching on power to
room appliance lights, fans has an effect on the observed potential.
So a part of the emf observed may be due to stray over induced by
external fields.
Potential difference netween electrodes, mV
Figure 5: Change in potential difference with time.
In absence of electromagnetic field
-6.5
-8.5
In presence of electromagnetic field
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-9.5
-10.0
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1381200
1385000 1386000 1387000 1388000
Time, sec
iii. The exact mechanism of production of this emf is not clear at present,
but it may be related to the corrosion, and may be due to impurities in
the electrodes setting of local electrochemical cells.
Figure 6: Effect of electromagnetic field in generation of emf.
Presented at Department of Chemical Engineering, University of Calcutta on December 22, 2012