Let's say you're pulling with acetone or IPA that's not 100% dry.
Then you do FASI or FASA on that.

It's my understanding that there are two problems with non-dry acetone/IPA:

1. It picks up base from your dry basic material.
2. DMT fumarate is soluble in water, so upon the application of FASI/FASA, some of your goodies will stay dissolved, which will result in product loss.

Now, suppose you put your FASA/FASI precipitation jar in the freezer. This should help the fumarates crash out of the water-containing solution, thereby mitigating at least problem 2. Am I right?

Problem 1. still remains and as a result you may get a neutralization product like sodium fumarate in your precipitate. But not if your acetone or IPA only picked up water (e.g. from the atmosphere) after the pull. So assuming you're starting with dry acetone/IPA and are worried it may have picked up water after the pull (e.g. during the FASI/FASA bombing, which can expose it to long periods of contact with atmospheric moisture), freeze precipitation should theoretically improve your yield?

You can test your theory by dissolving a known amount of DMT fumarate in water, adding a large excess of acetone or IPA, putting the solution in the freezer, and weighing whatever falls out. The acetone/IPA will not let the water freeze into ice.


How exactly would absorbed water improve your yield?

If you want to minimize the contact of FASA/FASI with water vapor drip it from a stoppered pressure-equalizing funnel (like this one) into a flask with the DMT freebase solution. Let it drip slowly and leave it alone.

Come back when it is done dripping, stopper the flask, put it in your freezer (DMT fumarate is almost insoluble in ice-cold acetone/IPA). Give it a few hours and then decant the cold solvent before it warms up. Dissolve the fumarate in a small amount of water and transfer that magic water into your evaporation dish - ideally with a syringe through a filter as that will leave most of the excess fumaric acid behind.