Cactus extraction -- any tips to improve yields?

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Xylene forms an azeotrope with water [the mixture boils lower than water], a few small traces are very easy to cook off of a solution. I use a coffee maker hotplate, as it heats water to nearly the boiling point of water-xylene without ever reaching the boiling point of water. It works so well I'm not afraid to drink the resulting water, in small single-dose amounts. Thats how I avoid messing with DMT goo or bothering to get DMT fumarate crystals.

I hate undershooting the pH during mescaline saltings, even with HCl since it leads to a less pure product as you noted [that yellow leads to orange mescaline and its a sticky black goo in its pure state] and I dont like having to add base to a solution that should just be mescaline and water. Theres one trick I use to minimize the risk.
Mescaline is somewhat soluble in water, you'll experience this when salting because you'll add a little acid and the water will still be like pH 8.5 due to a portion of mescaline freebase being dissolved in the water. While one can pull all the mescaline into water in one salting, with luck hitting pH 7.0, what I more often do is salt some of the mescaline into one portion of water, test the pH and set it aside, then do the same with another portion of water and add it to the first. These should be pH 7.5-9. Then if you undershoot on the last salting 1) it'll only effect a fraction of your mescaline and a smaller volume of water 2) you can slowly add it to the previous combined portions while monitoring pH, that free mescaline will help neutralize the excess acid 3) if you undershot by very little the final mix will still be basic and you can very carefully add the last needed quantity of acid without xylene being in the way, complicating things.
The pulls taken off when its still basic are quite clean, that yellow gunk comes over a little at neutral and a lot once you reach and go below pH 6. Whatever it is, its a weaker base than mescaline.
Its a good idea to have some very weak acid for the final stage of salting. I use 1M HCl for most of my salting, but I switch to 0.1M HCl at the very end [the equivalents with sulfuric acid would be 0.5M and 0.05M. 10% sulfuric acid is 1.02M, so not bad for most of the salting if your careful but some weak stuff would help at the end.]
The yellow/orange gunk can be removed by recrystallization or anhydrous acetone washes.

Thanks, that sounds like a good technique. I believe the xylene did boil off -- didn't know it formed an azeotrope with water.

Something strange happened while reducing the aqueous layer. The salting that I did perfectly and resulted in a clear aqueous solution -- I don't see any crystals at room temperature. The salting that I undershot the pH on and chased the pH to 6, resulting in a slightly yellow aqueous solution that smelled of xylene -- as soon as I finished the boiling it still looked yellow and clear, but when I added the equal amount of acetone it IMMEDIATELY formed a massive cloud of milky white precipitate. Into the freezer it goes. I'm hoping the clear solution forms crystals. If not, it's a good thing that I saved all of my xylene extracts.

 

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Final yield of 1.96 grams. The crystals aren't delicate crystals like I've seen in the pictures, but they are pure white and powdery, and much prettier than the HCl crystals I've made. If anyone cares, I think I would make the following changes to the procedure outlined in dg's simple ditration/dual solvent crystallization procedure:

- Ideally, use a separatory funnel. It's much easier than using a baster to decant the bottom layer.
- If a sep funnel isn't available, increase the amount of distilled water added to the organic extracts from 1/2 cup (~120ml) to 200ml, because it's easier to baste up a large volume of water than a smaller volume of water. Reduce the aqueous layer to the same amount (~50ml) in either case.
- Once the acidified aqueous layer has been reduced to about 50ml, don't add the acetone quickly. Instead, while the solution is still hot, slowly add acetone until the resultant solution begins to cloud up. This will most likely result in a crystal that is more pure. I base this advice on the dual solvent procedure found here: Labs | Chemistry Laboratory Techniques | Chemistry | MIT OpenCourseWare
- Gravity filtration with coffee filters isn't that great. It took forever to drain, and even then some of the crystals flow through the coffee filter, as evident by a milky white filtrate. An attempt was made to process the filtrate a second time but, again, it flowed through the coffee filter. Scraping the crystals off the coffee filters was also a pain in the ass, as the filters don't hold their shape very well. A cheap hand-operated vacuum filtration setup can be had for $30-50. A finely-fritted Buchner filter would probably work, although a porous Buchner filter might be better as the filter papers can be fine or coarse, as needed.

Overall, I'm happy. A 0.8% yield of dry material on San Pedro isn't too bad! Next time around, however, I think I will try pete666's STB procedure, Elrik's acidifcation advice, and my own suggestions. I might even try a hot-water recrystallization after the dual solvent crystallization, to get those beautiful mescaline sulfate needles I've seen pictured

 

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A disappointing update, I decided to recrystallize because I was suspicious of my yield. I added hot, almost boiling methanol and only a small amount of the crystals dissolved, indicating the remnants were most likely K2SO4 (insoluble in methanol) formed by the KOH brought over during extraction and the H2SO4 during the salting phase. I used quite a bit of methanol because I wanted to be sure the remnants were actually insoluble, so it's going to take a few days for it all to evaporate and I can determine my final yield. I'm not expecting much. :x