[verotxu]

Hello!

I am working with solutions containing n-butanol, dichloromethane, sodium chloride and water and I am trying to calculate the activity coefficients of the non-electrolytes. I have tried Aspen but with no much success. Any help?

Thanks!

[Rabn]

activity of non electrolytes in reference to what? In order to have an activity coefficient you need to have ions...no ion, no so called "atmosphere" around the atom/molecule.  You may want to look into the hydrophobic effect.  I'm kind of confused here.  You need to give us more of the underlying problem.

[Borek]

In order to have an activity coefficient you need to have ions...

That's Debye-Huckel, but solutions are not ideal also for reasons other than electrostatic forces. My memory fails me here, but I believe I have read there are observable differences between expected osmotic pressure and the real one. What better method to account for than activity coefficients? They just can't be calcuated this way.

[Rabn]

In order to have an activity coefficient you need to have ions...

That's Debye-Huckel, but solutions are not ideal also for reasons other than electrostatic forces. My memory fails me here, but I believe I have read there are observable differences between expected osmotic pressure and the real one. What better method to account for than activity coefficients? They just can't be calcuated this way.

All of those limiting laws have their quirks and necessities for accuracy.  I would suggest going the thermodynamic route but I have no idea what information this person has.

That's why I suggested the hydrophobic interaction route.  I'm curious as to the setup of this system.  It's hard to help out without anykind of way to visualize the system, i.e. volumes of each respective component.

[verotxu]

Hello!

In order to make the problem more clear..
I have in solution lets say 0,5 wt% of n-butanol, 0.5 wt% of DCM of 0.5 %wt of chloride. I am trying to see how the presence of salt effects the activity coefficient of the other compounds. I have read about it and the solutions might be to use UNIFAC, UNIQUAC model and then in order to take into account the ions add Debye-huckel to the equation. Any thoughts?. What is the hydrophibity interaction??

In order to have an activity coefficient you need to have ions...

That's Debye-Huckel, but solutions are not ideal also for reasons other than electrostatic forces. My memory fails me here, but I believe I have read there are observable differences between expected osmotic pressure and the real one. What better method to account for than activity coefficients? They just can't be calcuated this way.

All of those limiting laws have their quirks and necessities for accuracy.  I would suggest going the thermodynamic route but I have no idea what information this person has.

That's why I suggested the hydrophobic interaction route.  I'm curious as to the setup of this system.  It's hard to help out without anykind of way to visualize the system, i.e. volumes of each respective component.

[verotxu]

What do you mean with the thermodynamic route? The use of UNIFAC, Wilson....models?

In order to have an activity coefficient you need to have ions...

I would suggest going the thermodynamic route but I have no idea what information this person has.

That's why I suggested the hydrophobic interaction route.  I'm curious as to the setup of this system.  It's hard to help out without anykind of way to visualize the system, i.e. volumes of each respective component.