Ion attraction / repulsion trough glass...

[Externet]

Hi.

If a sealed glass container filled with salty water sits on a highly charged positive plate, and on its top a highly charged negative plate is placed; would the solution ions migrate towards the plates, leaving a leaner solution at the centre ?

Sort of a glass dielectric Leyden jar...

[John Cuthber]

Slightly.

You can calculate just how few ions need to move to produce a charge separation of the order you get in a Leyden jar.

 

A few pF or so at a few Kv means a few nano coulombs. Something like 10^7 electrons worth of charge. A molar solution of salt has something like 10^22 ion pairs (and about 100 times more water molecules) so the overwhelming bulk of the ions are not really moved.

 

To do the full calculation you need something like this

 

http://en.wikipedia.org/wiki/Debye%E2%80%93H%C3%BCckel_equation

[Externet]

Thanks, John.

Would time help in the migration ?

If ions happen to partially migrate under the electric field, is their (ions) interactive repulsion because they have the same charge polarity another limiting factor for greater segregation ? Ions of same charge do not 'like' to be piled up together.