Evaporation Formula?

[ksuchemist]

Hey so I know this sounds a little stupid but I need to find an evaporation formula for my current research project. Yes, I have looked around the internet but I keep running into formulas that only deal with homogeneous solutions or just water and I'm not sure if they apply to my case which is a little bit more complicated and I really want some opinions on which formula is best to use for this type of solution and please don't hassle me about how I should know this if I'm conducting research - I'm taking way too many classes to remember everything.

 

 

Here's what I'm doing and why I'm interested in evaporation:

I'm making polythiophene nanoparticles in which I have chosen the reprecipitation method that basically comes down to dissolving the polymer in THF and then injecting it into water to encourage colloiding. I'm trying to get uniform particle sizes that have yet to be made according to my literature research. I am concerned that when I am evaporating the THF out of the water that some of it may stay around and create an unstable colloid environment even at the smallest of concentrations which would thus effect the distribution of particle sizes. I understand this sounds ridiculous but I have to find a way to make these uniform particle sizes and I must eliminate every possible variable in my experiments. I'd rather not try to scrounge up a missive amount of samples and send them to the GC to figure out a week later where my sweet spot is for evaporation time where I could predict it by integrating a formula.

 

So does anyone have any suggestions on a formula for the rate of evaporation of a THF solution under partial vacuum evaporation? I would assume it must take into account pressure, partial pressure of THF and H2O, evaporation area, size etc. and I was hoping I could just integrate it over time to account for these variables changing.

 

Thanks ahead of time!

[John Cuthber]

This is as good a place to start as any

http://en.wikipedia.org/wiki/Raoult's_law

In general the assumption of linearity is probably more accurate at low concentrations.

Unfortunately the data you want has a lot of variables and I doubt that it is logged anywhere.

You will probably need to determine this experimentally.