My understanding is freebase DMT is VERY insoluble in distilled water.

I have been unable to find actual numbers and assume this is because it is so low that even with large batches the losses are effectively zero.

If this is true why would increasing the ionic strength of the aqueous layer have any effect on yields or efficiency. I understand how it would help if there was even a small amount of freebase DMT dissolved in the aqueous layer, but at a pH of 10+ there should be next to nothing remaining.

Can someone help my misunderstanding?

The (or an) answer is "it depends". Starting with DMT crystals, little will dissolve - but if you add base to a solution of DMT salt some may remain as a microemulsion and be very hard to get out of the water. This depends on things like concentration and temperature.

DMT freebase will dissolve into water when it can get protonated. Pure water will contain ~10^-7 molar of protons through its natural dissociation. But carbon dioxide dissolves in water and increases the proton concentration through the formation and dissociation of carbonic acid. This means that in practice, given very pure DMT crystals (no base or NPS contamination) you might be able to see more than a trace of solubility.

When you talk about increasing the ionic strength bear in mind that it then ceases to be distilled water.

The point of adding salt is that it helps to push the effectively non-polar DMT out of solution at a molecular scale while it is being formed through addition of base to a solution of a DMT salt. It also reduces the solubility of the NPS that will be pulling the DMT out of the aqueous phase.

Thank you so much!

So the salt really doesn't help get more DMT out of the base solution, but it helps speed up the process correct?

In a STB extraction wouldn't increasing the ionic strength of base solution push more bark breakdown byproducts like emulsifiers into your NPS?

It's likely there's an optimum which gives a balance between speed and yield. The Minimum Polymer explores things kind of relating to this - and in some detail.

That's likely a valid point you make about more impurities coming over above a certain ionic strength. But some of those impurities could co-solve the DMT and, off the top of my head, it's possible for this to be one factor behind the improved yields when increasing ionic strength.

I recall several conversations here over the years that address both base concentration and ionic strength with respect to extraction efficiency and the purity of the product. Unfortunately for now it's a bit late in the evening for me to go down the rabbit hole of digging them out.