SWIM was attempting to get a Pachanoi cutting to root for a few months. He was not very successful. After the last attempt, the cutting started becoming discolored, and SWIM worried that it was dying. Since SWIM already has some Bridgesii seedlings coming along nicely, he figured that he might as well sacrifice the cutting.

So, the Pachanoi cutting (only around ~13", weighing 140g wet) was cut into thin slices, which were then boiled in 1L of water and ~10g citric acid. When the liquid had reduced enough, it was poured off and new water was added. After this was boiled down, it was poured off. SWIM then mashed up the cactus slices to make sure everything was extracted, then boiled one last time. When pouring off this liquid, SWIM managed to spill some on his hand and scald himself. After a moment to appreciate his stupidity, he continued. The combined boils were reduced down to around 500mL, and added to a 1L glass jar. 50g of sodium carbonate was added, plus an extra 20g or so to neutralize any excess citric acid. Once all dissolved, around 300mL of sunflower oil was added. A white-grey precipitate formed when the oil was added, moving to the oil layer. SWIM has noticed this precipitate when mixing sodium carbonate solution with oil, and is very curious as to what it is. The solution was then mixed and let to sit overnight.

The next morning, the oil was poured off and mixed with 100mL of white vinegar. As much oil as possible was poured off before the rest was pulled off with a small syringe. SWIM finds that if the syringe is used to pull the bottom layer, there will be some oil that is pulled up as well. SWIM thinks this is due to oil being quite viscous. Once as much oil as possible is pulled off, the solution is poured into a coffee filter and drained into an evaporation dish. The last bit of vinegar in the filter is discarded before it can drain out, avoiding the small layer of oil on top from entering the evaporation dish. This process is repeated again with another 100mL of vinegar, and then the evaporation dish is left in front of a fan all afternoon to evaporate. After all the vinegar had evaporated, SWIM was able to scrape up ~100mg of an off-white, waxy powder. Anything that couldn't be scraped up was dissolved in a few mL of water and stored. SWIM plans to add this to a later evap. Another oil pull will be done later, and then washed with vinegar, etc.

SWIM was fairly surprised that the extraction worked, and is looking forward to the rest of the yield. He would like to hear any suggestions to help improve his method.

I'm going to be honest, all that "SWIM" crap is hard to read but I'm impressed you kept it in the 3rd person the whole time, most dont.

If it really worked have still to be tested, did you try the product?

I would suggest you to decrease amount of vinegar used for salting from non polar layer, you can save some time when evaporating it.
Overall, you used high volume of solvents for such small amount of cactus material.

Planning to try the product in a few days, once a few more pulls have been done. The second pull somehow yielded more than the first, which seems a bit suspicious... If the third pull yields a suspiciously large amount, the extraction will probably stop there. Is it possible that consistent yields on successive pulls are due to mescaline freebase having a low solubility in oil, or is it more likely that this is due to some kind of contamination?

Also, thanks for suggestions

IMO solubility in oil is quite ok, but I have never tried it.

Mescaline freebase is somewhat soluble in basic water, so mescaline does not migrate so easy to nonpolar as does dmt (which is insoluble in basic water)
Also, freebasing in water is sometimes not quick ( other compounds in water affect it), and if you do not wait some time after adding base, first pull could be inefficient.

Contamination with salt is also common, when nonpolar is not dried.

I'm sure you already know this. But I just want to point out that you could have stopped at this point and drank the 500ml of tea. And by doing that you would have consumed all of the mescaline that your water extraction yielded without having to resort to using oil or sodium carbonate, etc. Even the citric acid could have substituted with a little lemon juice. Much simpler and foolproof like that. Something to keep in mind for the next time. All the best.

Is there much reason not to do this, or is it just personal preference? For example, are certain undesirable alkaloids left behind when doing an A/B, or is the end product pretty much a full spectrum extract?

I've never done an A/B extraction, so I don't know if the final product is pure mescaline or not. Maybe someone else can chime in with the answer to that.

But I've drank cactus tea a bunch of times. Different species and clones of Trichocereus cacti have a different feel to them. There is more to these cacti than just the mescaline, in my opinion.

Water extracts mescaline (and the secondary alkaloids) out of the cactus better than anything else. Mescaline is highly soluble in water. Add some lemon juice to the water as the tea brews and you're all set. Then it is just a matter of reducing the tea down to a volume that is acceptable to you. The more you concentrate it down the harsher it becomes to drink, but the less of it there is. You can easily reduce a foot or 2 of thick cactus down to a few ounces of tea. All you need is water and lemon juice. Doesn't get much more food safe than that.

Today SWIM did another salting with vinegar (2 pulls, 20mL each), expecting to get maybe ~50mg of the whitish, waxy powder that he has gotten from the last two pulls. To his surprise, when he finished evaporating the vinegar, he found almost 300mg of tan, waxy crystals that could easily be scraped off the evaporating dish, much unlike the aforementioned whitish powder. SWIM truly has no idea what is going on here. How does a third pull yield more material than the first two combined, and a material that looks so different? Could it be due to the smaller amount of vinegar used? SWIM is happy but confused.

Wet cactus is around 5% dry mass, from your 140g piece it means 7g dried.
If you have 1% of actives in it, which could be real, you can got 70mg.

So, do not expect too much.

Contamination is mostly from incomplete separation of oil and water, and in your case, probably also due to some properties of oil.

This

Would you recommend any method of making this less likely? Or is oil simply not a great solvent?

Let settle oil undisturbed for some time before you separate it from water layer.

I would definitely recommend to do some final cleansing step (re-x or second A/B).
But you are working with small amount of material, so it is maybe not worth to do.

SWIM is doing their last pull over 2 days, so hopefully that will be more than enough time for oil to separate properly. Thanks for the replies, they've been really helpful

Also, I'm not sure if you have any experience working with oil as the NPS and sodium carbonate as a base, but would you know anything about the white precipitate that forms when oil comes into contact with a sodium carbonate solution? SWIM has tried adding clear oil to an entirely clear solution of 10% sodium carb, and a white precipitate instantly formed and migrated to the oil layer, making it cloudy. When left to settle over a few hours, much of the precipitate fell from the oil layer to the bottom of the water layer, but annoyingly, some stuck around at the very bottom of the oil layer. Any ideas?

Maybe some small water droplets of basic water suspended in oil, maybe some reaction between basic water. Really don't know exactly.
But it should be avoided, use just clear portion of oil. Filtering is also an option.