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ION–SOLVENT INTERACTIONS 187

2.22.2. Maximum Electrostrictive Decrease in the Volume of Water in
the First Hydration Shell

The definition of compressibility is

Then, 48

and after integration,

Although is known to decrease with increase of pressure, it is of interest to
make a first approximation by taking up to
10
pressures on the order of 10 Pa. Then, for omes

However, water cannot be compressed below the volume of the close-packed
structure, Hence, when the compressibility is taken as pressure inde-
pendent, the calculated effect of pressure becomes overestimated. What, then, is the
relation of to P?

2.22.3. Dependence of Compressibility on Pressure

It is known empirically that for water

Hence, at It can be seen that
a 22% decrease in compared with that at the standard condition of
5
10 Pa.

48
A pressure of atm is the standard pressure for reporting data, and it is denoted by a
superscript null after the variable, e.g.,