Error in A/B led to strange emulsion and purple naphtha

[Barnacle]

When performing an A/B SWIM made a minor error that led to some unexpected chemical phenomena. SWIM is trying to figure out what happened and would appreciate some help from the gurus here!

Here is the procedure SWIM followed:

- loaded 100 mg powdered MHRB into 6 paper tea bags
- twice boiled the bagged MHRB in 1.8L of vinegar solution (approxmiately pH=3, 125 mL 5% vinegar, 1675 mL tap water) for 1 hour at high pressure pressure directly in the stainless steel vessel of a pressure cooker (Instant Pot, 12 psi). Combined the resulting solutions to a combined 3.6 L (crude acidic extract)
- removed the tea bags; two of them had burst and significant sediment had leaked into solution, so SWIM let the crude acidic extract settle for several hours and decanted (decanted acidic extract), leaving a sludge at the bottom; however, lots of sediment remained suspended in solution
- vacuum-filtered the decanted acidic extract through a Buchner funnel with 20-micron pore filter papers (filtered acidic extract). Had to replace paper multiple times due to clogging; however, fine sediment still remained.
- reduced the 3.6 L filtered acidic extract to ~200 mL by boiling (acidic concentrate)
- vacuum-filtered the acidic concentrate through a celite pad to remove fine particles-- even this didn't seem to get all the sediment (filtered acidic concentrate)
- further reduced the filtered acidic concentrate to 150 mL by boiling
- defatted the room-temperature filtered acidic concentrate with ~100 mL of naphtha (defatted acidic concentrate). The naphtha used was clear but had been used on 2 previous extractions in a similar manner (defatting an acidic concentrate)
- mixed another 100 mL clean naphtha into the defatted acidic concentrate for extraction. Shook up separatory funnel to mix the phases. While separation was occurring, realized I had forgotten to basify the solution. Added 8 g crystal lye (calculated to achieve a pH of 12.5) into funnel and stirred. Lye dissolved but phases did not separate (emulsified basic concentrate).

So you can see SWIM's error was forgetting to add lye before performing the extraction. What confuses SWIM is that the extraction naphtha and basic concentrate did not separate when SWIM remembered to add lye. The emulsified basic concentrate was a dark purple-black, and didn't look like the emulsions SWIM has previously encountered. There was no layer separation at all, no bubbles-- just a thick uniform solution.

SWIM tried breaking the emulsion in various ways. In order:

- Heated solution-- this led to what SWIM assumed to be naphtha boiling off (temp stabilized at around 90C while some boiling was occurring), but did not lead to any layer separation.
- Added lots of sea salt (50 g?) to solution. It all dissolved but no layer separation.
- Added an additional 300 mL water. No separation.
- Added an additional 16 g lye. No separation.
- Finally, added an additional 100 mL fresh naphtha. Mixed the naphtha into solution with a magnetic stirrer. This naphtha then reseparated and seemed to take some of the emulsified naphtha with it-- an approximately 130 mL naphtha layer formed.

The formed naphtha layer was darker than any naphtha layer SWIM has seen before in an extraction. It was even kind of purplish, which SWIM has never seen (all the purple tends to remain in the aqueous layer).

SWIM washed this naphtha extract with 75 mL 10% sodium carbonate solution, which removed a fair amount of the coloring but not all of it. SWIM freeze precipitated it and got a mixture of nice white DMT crystals, crystals with purple impurities, and puddles of purplish resin. Note that the purplish impurities were *not* from solid plant material-- there were no visible solids in SWIM's extract.

SWIM is trying to figure out (a) what happened chemically; (b) what the best way is to clean the purple impurities from SWIM's precipitate.

Has anyone encountered something similar before? The key difference between this and other extractions SWIM has done is that SWIM added lye to an unseparated mixture of acidic extract and naphtha. Does the naphtha react with lye when it is exposed to it in aqueous solution?

 

[Tony6Strings]

I have had my naphtha turn dark several times, both during STB and A/B extraction. Upon freeze precip and drying of product, spice obtained was reddish in color. First time it happened I was upset and started searching the Nexus for answers. Later that evening I smoked some and it was great. Loved it. Now I welcome the occasional pull of red spice.

 

[Infundibulum]

You can do a mini A/B on the crystals including defatting and see if that removes the colour.

Could somehow your mhrb be cut with something else?

also

Added 8 g crystal lye (calculated to achieve a pH of 12.5)

You cannot realistically calculate how much lye to achieve target pH by any simple or more complex formula. Plant extracts are fairly complex in their composition and buffering capacities.

What you did later, i.e. add more lye was the right thing to do.

 

[Barnacle]

Thanks good people.

@Tony6Strings

Good to know you've seen something similar before. This is reassuring. SWIM has never vaped red-purple spice, but he may try it.

@Infundibulum

SWIM will try the mini A/B on the bulk of the product. SWIM has used the same MHRB batch for 4 other extractions without running into this issue, so I doubt it is cut.

Regarding pH, good point-- SWIM realizes what he is doing is approximate due to the various compounds in the plant extract, but some sort of calculation is useful if one is experimenting with reducing the extract to different volumes before basification.

The calculation SWIM uses is to add the molar equivalent of the acetic acid in lye, at which point the solution is approximated as neutral, then add the same amount of lye to achieve target pH that one would add to water. SWIM has tested this approximation before by measuring the pH after lye addition with a digital pH meter and it is ballpark-correct (within +/- 0.5 pH units).

 

[metta-morpheus]

Not sure if it’s related, similar conditions though. On my first extraction I basified, and immediately put naphtha in after, before lye had fully reacted. Goal was to utilize the heat from reaction to warm solvent (just use hot water bath!). Only time I’ve had a redish brown naphtha pull. Now I let lye fully react for 10-15 minutes before adding solvent.

And you don’t need to swim here any more...

 

[Barnacle]

@metta-morpheus

Your experience sounds very similar to mine-- good to know of someone else replicating at least part of the phenomenon. Do you recall if your naphtha easily separated?

Regarding "SWIM"-- haha OK. Most of my reading of the forum has been old posts I guess that I searched for. Wasn't quite clear what the convention was since SWIM is used inconsistently.

And now that @metta-morpheus says he has seen the same, let me reformulate the key question of this post for those with the most chemistry knowledge:

Does lye react with naphtha when exposed to it in aqueous solution? Or does the presence of naphtha somehow catalyze reactions of lye with other products?

If the answer to either of these questions is yes, I am puzzled. Because lye in aqueous solution is simply solvated Na+ and OH- ions, I don't understand why it would matter if lye is added before or after mixing in naphtha. In either case, the naphtha is going to be in an aqueous solution with a lot of OH- ions.

Maybe instead some reaction between naphtha and something in MHRB happens exclusively in the pH range in between the acidic and basic endpoints? If one adds naphtha at the same time as lye, then the naphtha would be exposed to this middle pH range as the lye dissolves. But if the naphtha is added after the lye has fully dissolved, then it will never be exposed to this middle pH.

 

[bismillah]

Try smoking it, and if it turns you purple, then we know it's dangerous.

 

[metta-morpheus]

Maybe instead some reaction between naphtha and something in MHRB happens exclusively in the pH range in between the acidic and basic endpoints? If one adds naphtha at the same time as lye, then the naphtha would be exposed to this middle pH range as the lye dissolves. But if the naphtha is added after the lye has fully dissolved, then it will never be exposed to this middle pH.

This is a logical hypothesis. Maybe a way to test this theory is to add tiny amount of lye to reach a stable mid ph, but let fully react before adding naphtha to see if it is caused by ph or the lyes chemical reaction with acidic solution.

 

[downwardsfromzero]

Maybe instead some reaction between naphtha and something in MHRB happens exclusively in the pH range in between the acidic and basic endpoints? If one adds naphtha at the same time as lye, then the naphtha would be exposed to this middle pH range as the lye dissolves. But if the naphtha is added after the lye has fully dissolved, then it will never be exposed to this middle pH.

Does lye react with naphtha when exposed to it in aqueous solution? Or does the presence of naphtha somehow catalyze reactions of lye with other products?

No. Naphtha will not react with lye under these conditions. It is practically inert.

A middle pH range is known as 'neutral'. Like water. Naphtha does not react with water. It won't act as a catalyst either, even in a fairly lax sense. The problem was caused mostly by physical factors, in my view.

Here are some thoughts on what might be happening. It appears the acidic bark absorbs naphtha fairly readily. (A scenario that would require experimental confirmation: It could be that the naphtha dissolves something under acidic conditions - fatty acids or phenolics for example - which then become insoluble in naphtha when deprotonated after addition of lye. This will cause the formation of small particles of, literally or effectively, soap - which will turn the whole mixture into a horrible mess, as you found out.)

I think it's mostly surface effects, though. The lye helps break down the woody material, and also makes it more repellent to the naphtha by forming negative charges on the surface of the particles. Because of their relatively greater surface area the smallest particles get digested first - and it's these tiny particles that can also promote emulsion formation rather effectively.



Also this was of note in the first post:

lots of sediment remained suspended in solution

This sediment would have been dissolved by the lye had it been added first. Instead, the naphtha stuck to it and the lye was unable to get to it properly. [It's also worth knowing that acidic MHRB tea dumps out LOTS of gloopy tannins on cooling.] Some patience here - leaving the brew to settle for 24 hours in the refrigerator - would have paid dividends. That, and attention to detail...

To reiterate, it is important in which order you add the extraction materials because acidic bark particles seem to absorb naphtha a lot more effectively than alkaline (basic) ones - and the lye needs to react with the bark unhindered. There are many other processes in life where the sequence of actions is important, it should be simple enough to think of examples.

 

[Barnacle]

@bismillah

LOL, probably gonna pass... but you're welcome to run this experiment yourself!

@downwardsfromzero

Thanks for the thoughtful and knowledgable reply.

A few questions/comments:

- I understand that water is neutral at pH 7. But the "middle pH range" we are talking about here is large-- around 2.5 or so all the way up to 12. There are many non-neutral pH values in this range that are significantly different from the endpoints. As the pH evolves over this range, various molecules in the MHRB are going to temporarily enter different states of protonation. The question was not whether naphtha reacts with water, but whether naphtha might react with some chemical species that is present at one of these intermediate values, but not at either endpoint.

- Thanks for the confirmation that lye is not reacting with naphtha.

- When I defatted the acidic MHRB concentrate as described above (150 mL) with 100 mL naphtha (by throughly mixing with magnetic stirrer), I got virtually all of the naphtha to separate out quickly. Doesn't this suggest that the naphtha was not absorbed particularly easily by the acidic bark? Similarly, if the small particles you mention are most effective in emulsion formation are present in the acidic solution, why did my acidic solution not emulsify during defat?

- The idea that the changing solubility of some molecule X in naphtha leads to emulsion seems most intriguing to me. This is because it seems clear (based on past experience working with naphtha in both acidic and basic MHRB teas) that the issue has something to do either with (a) naphtha being mixed into solution while the pH is *changing*, or (b) naphtha being mixed into solution somewhere in the "middle pH range". Could you elaborate on how the hypothesized change in solubility of molecule X in naphtha leads to the formation of "soap" (micelles?). Don't soap molecules have a polar head and a nonpolar tail, with the tails facing inward and the heads facing outward into the aqueous phase? How would something similar occur due to the changing solubility of molecule X in naphtha?

- Thanks for the tip on cooling the tea. I have never done this before and will do so in the future.

 

[downwardsfromzero]

OK, I see what you're saying here. Maybe my top-of-the-head ramblings sounded over-definitive It makes sense, then, that the acidic bark would be somewhat positively charged and therefore more repellent to the naphtha.

Also, I should practice my reading comprehension As you said earlier:

if the naphtha is added after the lye has fully dissolved, then it will never be exposed to this middle pH.

There probably is some kind of charge/pH-related phenomenon somewhere between a pH value of 2.5 and 12. At some point between, the particulates become particularly (!) sticky towards naphtha, or some kind of species is produced that optimally emulsifies with naphtha and breaks only with difficulty on raising the pH fully. Perhaps this is the purple substance that seemed to be trapped in your naphtha? Or that could just be fine particulates - maybe microscopy (or a centrifuge) would help here.

Modifying my earlier (qualified) statement somewhat: changing the pH from low to high of the bark extract causes it, or more specifically, suspended solids within it, to pass through an essentially neutral charge state which is apt to combine with naphtha via surface (Van der Waals) effects. This leads to the rather intractable emulsification and possibly a naphtha-soluble purple fraction. The particulates resist reacting with the lye because they have become coated with naphtha - that is my current best guess based on the information given.

The statement I will stand by is that the naphtha will not be undergoing any chemical change with the reaction conditions you describe. It is practically inert.

 

[Barnacle]

@downwardsfromzero

Modifying my earlier (qualified) statement somewhat: changing the pH from low to high of the bark extract causes it, or more specifically, suspended solids within it, to pass through an essentially neutral charge state which is apt to combine with naphtha via surface (Van der Waals) effects. This leads to the rather intractable emulsification and possibly a naphtha-soluble purple fraction.

Thanks, this hypothesis makes a lot of sense. Here is an experiment that could test this:

An acid boil of powder is done and the result is crudely filtered and reduced as described in my first post in this thread. Then several samples are taken and basified with lye to different pH values from ~2.5 (no lye) all the way up to ~12.5 or so (fully basified). Then try mixing equal volumes of naphtha (the procedure I followed used a ratio of 3:2 concentrate:naphtha) into the samples and see whether there is a difference in emulsion formation.

Unfortunately I'm out of MHRB powder and my next batch is shredded, so I won't be able to do this in the near term, but if anyone else wants to run this experiment it would be great... Or if anyone reading has a source (past thread on the nexus or otherwise) that sheds further light on the tendency of MHRB to emulsify at different pH levels, please post the link!

 

[Friday10]

Sorry to bring up an old post but I’ve just come across the same thing that’s also combined with a hideous emulsion. So bad that I cannot separate the naphtha at all. It is basically a purple naphtha filled sludge. Does anyone have any tips on how to proceed? Would be an awful shame to lose 500g

 

[downwardsfromzero]

Sorry to bring up an old post but I’ve just come across the same thing that’s also combined with a hideous emulsion. So bad that I cannot separate the naphtha at all. It is basically a purple naphtha filled sludge. Does anyone have any tips on how to proceed? Would be an awful shame to lose 500g

Please describe exactly what you've done to get to this state. And maybe consider the wisdom of sticking to smaller batches. Eggs, baskets, etc. :roll:

 

[Friday10]

My last 500g extraction went pretty well so was hoping for the same again. Normal a/b extraction but it would appear that the lye had not finished reacting with the naphtha before I put it in. It turned into a purple sludge in the naphtha which was jelly like in texture. Can this be saved?

 

[downwardsfromzero]

My last 500g extraction went pretty well so was hoping for the same again. Normal a/b extraction but it would appear that the lye had not finished reacting with the naphtha before I put it in. It turned into a purple sludge in the naphtha which was jelly like in texture. Can this be saved?

Presumably you mean the lye hadn't finished reacting with the bark?

That was identified as the problem in this thread - intermediate pH level allows the naphtha to soak into the bark too easily. Were you in some kind of hurry?

How many 500g extractions does one person need to do in one lifetime? Have a read of this:
2.10 No commercial-scaled extractions and reckless “spreading” and have a think about your intentions.

The solution to your difficulties should already be covered in this thread or another one nearby. Have a read back through the posts. According to your technical understanding of the extraction process, what do you think can be done to rescue the extraction?