Chemistry Reference
In-Depth Information
Table 9.14
Resistance,
R
(
W
) measured in the electrochemical cell at certain time,
t
(h). Between the short
R
measurements, the textile electrodes were immersed in
NaCl, artificial sweat, waste-water solutions or water. (Knit: knitted; wov: woven;
nonw: non-woven.)
NaCl (0.2 mol l
-
1
)
Time
rtificial sweat
Waste-water
Water
(h)
solution
Knit
Wov
Nonw
Knit
Wov
Nonw
Knit
Wov
Nonw
Knit
Wov
Nonw
20
300
301
259
298
301
254
510
476
810
298
300
261
25
302
301
258
306
309
258
897
1013
1249
301
301
258
30
304
306
254
309
314
271
1584
1644
1874
306
302
259
35
303
309
259
315
320
286
2241
2200
2584
304
306
261
40
310
314
271
328
331
299
3036
2978
3456
307
305
260
45
317
321
288
337
346
317
3986
3874
4243
299
304
264
50
329
328
301
356
358
346
4196
4003
4316
306
308
267
70
341
339
315
381
378
371
4288
4185
4377
300
309
266
100
350
347
332
403
410
395
4284
4274
4401
298
304
268
200
358
358
336
415
425
403
4298
4345
4425
299
305
264
500
370
369
349
430
436
410
4308
4392
4463
302
307
268
on the condition that at this frequency no phase-angle shift (q=0°) is
observed between the applied potential and measured current that is
obtained. From Fig. 9.9b, it can be seen clearly that a frequency of 10 000 Hz
is the most optimal value to fulfill this condition.
Textile electrodes were immersed in solutions of NaCl (0.2 mol l
-1
) in arti-
ficial sweat solutions with a similar NaCl concentration, in waste-water from
a textile-finishing company and in water. The first three solutions were
expected to affect the textile electrodes intensively due to chemical attack,
adsorption phenomena, etc. The fourth solution was not expected to have
a serious influence. At certain time intervals, the electrodes were inserted
in a test cell (see section 9.2.2) for the determination of the cell resistance
when using a 0.1 mol l
-1
NaClO
4
solution; and then placed back in the NaCl,
artificial sweat, waste-water or water solution. The data are shown in Table
9.14. It can be seen that only the electrodes immersed in water remain at
their initial value, and therefore their quality remains constant. For the elec-
trodes immersed in NaCl and artificial sweat, a slow and continuous
increase of the resistance is observed due to the attack on the textile elec-
trode surface by chloride. This initiates a corrosion reaction with the for-
mation of metal oxide, metal hydroxide and metal chloride depositions that
are less conductive than the metal, thus contributing to the resistance of the
cell. An increase of 10% of the resistance can be seen as substantial and
outside the limit of twice the standard deviation; thus for a resistance
increase of 10% against the initial value of a new (not used) electrode, it
can be concluded that the quality is no longer guaranteed and the electrode
