Freezing Point Changes?

[Hacp]

Hey guys, I have a really simple question to ask. I'm looking at a problem where I have a solution of an ester(10-20 mole%) in water. The ester has a high melting point, lets say 70C. Does anyone know how I can predict the temperature where the ester-water solidifies to form a slurry? I do not have access to a phase diagram so are there any semi-empirical formulas out there that can help me?

 

[Paperdoc]

No. The phase diagram of a binary system of two liquids depends entirely on which liquids, and is unique. There is no general formula for this sort of thing.

The closest you could get is finding (if possible) the Molal Freezing Point Depression constant for this solute (ester) in water. But even that does not quite do it, because the concept there is that the Freezing Point Depression is a LINEAR function of Molality, which only occurs at very low concentrations. It is not good for extrapolating along the curve of the phase diagram all the way to the eutectic point.

 

[Hacp]

No. The phase diagram of a binary system of two liquids depends entirely on which liquids, and is unique. There is no general formula for this sort of thing.

The closest you could get is finding (if possible) the Molal Freezing Point Depression constant for this solute (ester) in water. But even that does not quite do it, because the concept there is that the Freezing Point Depression is a LINEAR function of Molality, which only occurs at very low concentrations. It is not good for extrapolating along the curve of the phase diagram all the way to the eutectic point.

I was hoping someone had come across some relation that would be helpful. The closest I could find was this paper "Estimation of Freezing Point Depression, Boiling Point Elevation and Vaporization enthalpies of electrolyte solutions". It states that their derived correlation was for electrolyte solutions, however, the derivation did not seem specific to electrolytes.

I think I might be able to obtain a reasonable number using Uniquac to estimate the activities, then the formula from that paper to estimate a freezing point depression. I might also need to approach the eutectic from both sides just to see whether the curve turns on me before 20 mole%.