Page 250 - MODERN ELECTROCHEMISTRY

186 CHAPTER 2

Fig. 2.75. (a) Local compressibility of
water as a function of log(field) near an ion.
(b) Electrostriction, in water as a func-
tion of log(field) near an ion. (Reprinted
from B. E. Conway, Ionic Hydration in
Chemistry and Biophysics, Elsevier, New
York, 1981.)

Now,

where is the force of the ion on the water molecule at a distance r from the ion.
Therefore,

The force calculated here is upon a water molecule in the hydration shell. If
one takes the cross section of the water as the pressure (pressure = force/unit