Selection of our books indexed in the Book Citation Index in Web of Science™ Core Collection (bkci)

Primary Metal and Chemical Reaction
Half-cell Potential
Al → Al
3+
+3e
-
-1.706
Cr → Cr
3+
+3e
-
-0.744
Cd → Cd
2+
+2e
-
-0.401
Zn → Zn
2+
+2e
-
-0.763
Fe → Fe
2+
+2e
-
-0.409
Ni → Ni
2+
+2e
-
-0.230
Pb → Pb
2+
+2e
-
-0.126
H
2
→ 2H
+
+2e
-
0.000(stand by definition)
Ag → Ag
+
+e
-
+0.799
Au → Au
3+
+3e
-
+1.420
Cu → Cu
2+
+2e
-
+0.340
Ag+Cl → AgCl+2e
-
+0.223
Table 2. Half-cell Potentials of Important Metals
→ Fe
2+
+2e
-
→ Ni
2+
+2e
-
→ Pb
2+
+2e
-
→ 2H
+
+2e
-
→ Ag
+
+e
-
→ Au
3+
+3e
-
→ Cu
2+
+2e
-
→ AgCl+2e
-
(a) Flexible Mylar electrode 
(b) Disposable snap-type Ag/AgCl electrode 
Figure6.12 Biopotential skin surface ECG electrode 
Figure 13. Biopotential skin surface ECG electrode
2.7.2. EMG electrodes
Electrochemical electrodes are also used to record electromyography (EMG) signals from
different muscles in the body. The body and size of the recorded EMG signals depends on the
electrical property of these electrodes and the recording location. For invasive recordings,
proper skin preparation, which normally involves cleaning the skin with alcohol or the
application of a small amount of an electrolyte paste, helps to minimize the impedance of the
Biomedical Sensor, Device and Measurement Systems
http://dx.doi.org/10.5772/59941
195

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skin-electrode interface and to improve the quality of recording signal considerably. The most
common electrodes used for the surface EMG recording and nerve conduction studies are
circular discs, about 1 cm in diameter, that are made of silver or platinum. For direct recording
of electrical signals from nerves and muscle fibers, a variety of percutaneous needle electrodes
are available as illustrated in figure 14. The most common type of needle electrode is the
concentric bipolar electrode as illustrated in figure 14a. This electrode is made from the thin
metallic wires encased inside a larger canola or hypodermic needle. The two wires serve as
the recording and reference electrodes.