Re: dielectric constant of water

[Pentcho Valev <pvalev@BAS.BG>]

On Fri, 22 Aug 2003 21:34:15 -0400, Wolfgang Rueckner
<rueckner@FAS.HARVARD.EDU> wrote:

> Ahhh -- I now see the problem; thank you.  But I still fail to
> understand why then (if water conductivity is the issue) different
> plastic bags produce such radically different results.  And even with
> the same plastic, varying the thickness of the bag makes a big
> difference.  --  Wolfgang

In my view, the effect is due to the so-called clathrate water which is
formed in the vicinity of hydrophobic surfaces (in this case the surface of
the wall of the bag) and is sometimes called "water of hydrophobic
hydration". When the wall is thin, there is polarization, i.e. "water of
polar hydration" is formed near the surface and you measure a high
dielectric constant. However if the wall is thick, water of hydrophobic
hydration predominates - it forms many layers with almost no polarization.

It would be curious to somehow measure the attraction between the plates,
on condition that water is allowed to exert pressure on the plates. I
expect the attraction to obey a "dielectric constant" with properties quite
different from the dielectric constant you have measured.

Pentcho Valev