Charge balancing

[P Rousseau]

I have two questions regarding charge balancing (mostly considering REACT).

 

Firstly, why is charge balance reported in Faradays. I can understand that it is calculated as such from the numerical solution, but it seems impractical as a measure of the ionic balance. Is there any particular reason why it is reported this way, instead of as a percentage difference? The variable significance of the charge difference with changing ionic strength is of particular interest in this case.

 

Secondly, what is the effect of turning off the charge balance option. I have dealt with a few solutions lately that are difficult to solve in terms of charge balance, as the likely ions result in an unstable model if allowed to act as the charge balancing species. In the end it required iterative adjustment of the alkalinity (the only easily questionable variable that could be manipulated in good concience) to achieve a reasonable charge balance.

 

I hope someone might be able to provide a bit more insight than I seem to be able to find in the literature.

[Tom Meuzelaar]

I have two questions regarding charge balancing (mostly considering REACT).

 

Firstly, why is charge balance reported in Faradays. I can understand that it is calculated as such from the numerical solution, but it seems impractical as a measure of the ionic balance. Is there any particular reason why it is reported this way, instead of as a percentage difference? The variable significance of the charge difference with changing ionic strength is of particular interest in this case.

 

Secondly, what is the effect of turning off the charge balance option. I have dealt with a few solutions lately that are difficult to solve in terms of charge balance, as the likely ions result in an unstable model if allowed to act as the charge balancing species. In the end it required iterative adjustment of the alkalinity (the only easily questionable variable that could be manipulated in good concience) to achieve a reasonable charge balance.

 

I hope someone might be able to provide a bit more insight than I seem to be able to find in the literature.

 

Hi Pierre:

 

Sorry for the delay in response- we've been working hard with getting the new RockWare website up, and restoring the forum back to normalcy.

 

A faraday is just a mole of charge. Different people interpret fractional charge imbalance in different ways: relative to total charge on cations or anions, the average of the absolute values of those number, total charge on ions of charge like or opposite to the charge imbalance, and so on.

 

If you turn off the charge balance option, React simply proceeds forward with an imbalanced solution.

 

I hope that is of some help.

 

Regards,

 

Tom Meuzelaar

RockWare, Inc.