Page 50 - MODERN ASPECTS OF ELECTROCHEMISTRY

Voltaic Cells in Electrochemistry and Surface Chemistry of Liquids
37
adsorption at the oil/air interface should be small and is practically
negligible.
Adsorption of a dipolar substance at the w/a and w/o interfaces
19
changes surface tension and modifies the surface potential of water (Fig.
11). As seen in Fig. 11, the change in compensation voltage ∆E due to
adsorption is the surface potential difference, usually called the surface
potential, or better the adsorption potential, and often indicated unneces-
sarilyby ∆V. 4–8
∆E =∆χ = χ – χ W+B
W
W
(24)
The experimental investigation of ∆χW maybe performed directly as
presented in Fig. 10 or by using two alternately measuring cells (XI) and
(XII). In the first case, a voltaic cell with a differential ionizing probe or
the jet method can be used. In the second case, the ionizing probe or
vibrating plate method is applied (see Section IV).= These probes are two
versions of a so-called air electrode that assists in the measurement of a
voltaic cell as illustrated in Fig. 10. The air electrode, e.g.,= the vibrating
plate, creates in fact the two following cells:

|
w |
M vib.pl gas | ref.© M,E 11 (XI)
MX
|

Figure‰1. Influence of the adsorbed molecules B on the surface
potential of water.=