During manske, Cl- ions are added (typically using NaCl) to a harmalaH+ solution (typically from rue seed water extraction). The solution is cooled, and the presence of the common Cl- ion precipitates harmalaHCl. Remaining liquid is removed (along with unwanted plant material) and the precipitated harmalaHCl recovered.

For manske to work, both Cl- and harmalaH+ concentrations need to be chosen appropriately:
a) If Cl- concentration high, salt contamination will increase along with unwanted plant material (e.g. proteins) that could precipitate at high ionic strength.
b) If HarmalaH+ concentration is too high, there may not be enough water to remove unwanted plant material.
c) If either are too low, precipitation will be insufficient or not occur.

Following a good tek avoids these issues 🤞. For those interested in more details 🤓, we can look at the equilibrium equation as an approximation to the complex plant extract.

Definitions:

c: Molarity of shared chlorine in ions before precipitation.
h: Molarity of harmalas before precipitation.
s : Solubility of HarmalaHCl in cold water. By definition, it is directly related to the HarmalaHCl(↓↓) <--> [HarmalaH+] + [Cl-] equilibrium constant: K = s^2. For manske purposes, a mixture of two saturated harmalaHCl salts (e.g. harmine and harmaline) behave as a single harmala with solubility s(Mixture)^2 = s(Harmaline)^2 + s(Harmaline)^2.
r : Harmala recovery ratio after precipitation.

From these definitions, when precipitation is complete, rh of [harmalaH+] and [Cl-] will have precipitated as HarmalaHCl, leaving h-rh of [harmalaH+] and c-rh of [Cl-] in solution. The equilibrium equation for harmalaHCl(↓↓) <--> [harmalaH+] + [Cl-] is therefore:



An important first observation in this equation is that when r = 0 (no recovery), hc = s^2. That is, precipitation will not happen until hc > s^2, quantifying part of bullet point a). Eq 1. can be re-arranged to express r as a function of c, h, and s:



For example, for h=0.07M and s=0.05M, the expected recovery r can be plotted against c:



One question that comes up is, "How much salt do I need to add?" Eq. 1 can also be re-arranged as:



The salt needed can be plotted as a function of h (for example, for r = 0.98 and s = 0.05M),



The minimum represents the manske setup where 98% recovery can be achieved with the lowest Cl- concentration. This important point is given by,



In our last plot (s = 0.05M, r=0.98 ), the minimum salt point is at h0 = 0.36M and c0 =0.70M (4.09% NaCl). Compared to the other examples, if 6g of FB harmalas are dissolved in 78ml (instead of 400ml), the added NaCl salt concentration can go down by a factor of ~2.6 (from 10.8% to 4.01%) and the same ammount of harmalas will be recovered.

Since excess water helps remove unwanted plant material, harmala dilution away from the lowest salt concentration point could be useful. Let's call the dilution factor 𝛼,


The salt concentration to keep the same recovery rate increases to,


In our ongoing examples, h = 0.07 was 𝛼 ~ 5x dilution from the minimum salt point (h0=0.36M). Consequently, the NaCl salt concentration was ~ 1/2*(5+1/5) ~ 2.6 higher.

Issues can arise if h is too dilute (large 𝛼, as the required c will not be reachable.

These examples are only quantitative until s is actually measured/known. I think there are a few conclusions we can make though,

1) The ammount of salt needed is highly dependent on the starting harmala concentration.
2) There is a starting harmala concentration that minimizes the NaCl concentration needed.
3) In practice, diluting the harmalas below the minimum NaCl salt point may be desired to remove excess plant material with the help of additional water, but the NaCl salt concentration will need to increase.
4) By knowing the HarmamaHCl solubility in cold water (s), all these quantities can be calculated and set up. For a desired r:
4.1) Calculate the minimum salt point (h0, c0) using Eq. 4. If excess water is not needed perform the manske there.
4.2) If more water is desired, decide on a dilution factor 𝛼 which will determine a new h and c using Eq. 5-6.

There is a special dilution value that minimizes the combined ionic strength h+c. It can be shown a minimum occurs for h+c when 𝛼 = √(1 + 1/r). In Fig 2. that corresponds to where the slope of the curve is -1, which occurs at h = 0.25M, c = 0.75M.


Note: Heavily edited on 12/1/2020. Images are linked to chat, also adding them here in case they are lost during a hard chat reset.

Thanks for this! It's coming in handy for some of my mental reckoning in exactly this matter right now.

Sorry to be picky, but your graphs would be easier to read if the axes were labelled.

They do make sense but I had to look at them for a while before working out what was being plotted against what! (I never said I was clever )

I have nearly two litres of spent Manske solution which is basically saturated with NaCl but still displays significant fluorescence. My harm.hydrochlorides recovered from 50 g of rue have been redissolved in ~375 mL water (which is what was required to dissolve them out of the Buchner funnel) and acidified to ca. 1% with acetic acid. The experiment will be to reuse the spent Manske solution by adding about 187.5 mL of it to the redissolved alkaloids to bring the salt concentration to roughly 10%.

So, having cast my eye over your equations it appears that my plan might work.

The synchronicity is quite remarkable

Yeah, sorry about the axis. Plots are made with wolfram alpha on my cell phone. Here are the full links in case it helps (input can be modified to play around with the equations). If you can figure out how to add axis I can update the plot,

Rate of recovery (r) vs moles of salt needed relative to moles of harmalas (c/h) for initial condition s/h = 0.5 (starting harmala acetate concentration is double the HarmalaHCl solubility measured in moles).
Salt concentration needed (c) vs. starting harmala concentration(h). Recovery rate set to 98% (r = 0.98 ), and HarmalaHCl solubility assumed to be 0.05M (s = 0.05)

Knowing the HarmalaHCl solubility in cold water would really help in testing/predicting good manske conditions. If anyone has that, would be great to share. For simplicity I've been considering that we are looking at one harmala...

Maybe you can also try reducing the spent solution volume by boiling. While hot, the saturated NaCl will crash, but the dilute harmalas may not. If so, you can filter the salt a few times as you boil until you are down to about 1/5 of the starting volume. Then add some water to give the salt room before cooling (maybe back up to 1/4 of the initial volume). In practice, you would have increased h by a factor of 4, which can be very important and make a big difference if your spent harmala solution is on the left side of the c vs h plot, (hypothetically, if your starting was h ~< 0.05M on the spent solution you would have pushed it to h ~< 0.2M).

Boiling down the spent solution seems worth a try. The salt crystals will simply sink for the most part, sodium chloride has the advantage of forming large enough crystals during evaporation by boiling. The acidity of the solution will creep up somewhat, though. Maybe I'll boil it down in batches as distillation and recover some very dilute acetic acid as well as the salt, thus saving myself some of the stink.

[I'm actually quite interested to see if any of the chloride volatilizes as HCl when salt is boiled with vinegar. It's easy enough to test the distillate with a bit of silver nitrate. And yes, I do have the necessary equipment to minimize spray carry-over from the boiling flask. Apologies for the tangent!]

Thanks for the ideas, I'll report back. It would be nice to contribute some experimental data/figures to your work (once I get something I can be bothered to weigh).

My apologies, the equations and figures at gone. I guess wolfram alpha only keeps them for a limited time

Not to worry, at least for me this has been helpful. Also, it should be possible to recreate the equations and graphs without excessive difficulty. I might take a look on the internet archive/wayback machine to see if something got stored.

Edit: the hyperlinks in your text still produce the desired output directly on wolfram alpha, so all is not lost!

Yeah, that's good. Thanks!

I tried to look at manske with two harmalas (h1, h2). Each harmala has it's own equilibrium equation and the formulas grow a lot, but there is a very nice simplification that I hope is reasonable: Assume the two harmalas behave the same way in solution (same starting concentration and same chloride salt solubility). The total recovery simplifies back to the simple form in the first post (as if we had one harmala) with s^2 -> 2s^2 (all else unchanged).

In other words the two different harmalas behave as a single harmala with the effective chloride salt solubility increased by √2 ~ 1.41 higher solubility (~ +41%) for the chloride salt (more difficult to precipitate compared to a single harmala).

DWZ, the original post has been edited for clarity and axys have been added. Cheers.

I made a crude measurement of cold water HarmalaHCl solubility (mix of harmine/harmaline from rue). Very crudely, it was measured at s~0.1M (lab notes in spoiler). This is 2x higher and consistent with the guess in post #1, not too bad 🙂.


Using Eq. 2 in post #1 (which again, may not work well for plant extracts) and assuming the measurement s=0.1M is a good approximation (it may not be), we can now check the predicted recovery rate r for different manske setups (h,c).

- EHFBT: OK recovery, but appears to loose some harmalas due to dilution (low h). If one dilutes further (e.g. starts with low yielding seeds or has an issue during basing) the yield could fall of a cliff. On the plus side, the dilution will remove a lot of unwanted plant material.
- VDS: Less dilute than EHFBT and more robust for yield. Still, a small systematic loss in yield is possible. In the protocol (section 3.2) it is mentioned that there where "very small and stable" precipitates when basing the manske supernatant. This "small and stable" material could be the harmalas that systematically don't precipitate since r~98% (and could add up after 5x repeats to ~10% loss). On the plus side, the dilution helps with the cleanup.
- Tao1: First option in the tao of rue extraction. Good recovery rate and low salt, but removing unwanted plant material will be hindered because of low volumes. On the plus side, this setup has the lowest salt contamination.
- Tao2 (Phlux): This seems to be a sweet-spot. Yield is robust and stable to experimental variability. Won't remove as much plant material as VDS or EHFBT and will have more salt than Tao1, but it all looks like a good compromise.
- Tao3: Salt overload which does not impact yield. Does not seem necessary, and in the tek itself it is mentioned that this option is not preferred.

Perhaps, a good strategy would be first do manskes at h ~ 0.17M with heavy salt (c~4.4M) so the extra water helps remove plant junk. Then move to a more concentrated h~0.7 and use less salt (c ~ 1.7M) to remove any proteins that precipitate at heavy salt concentrations (if any) and reduce salt contamination. In general doing manske at two separate points in the contour plot while fixing the recovery rate for harmalas could help separate out different contimants at each chosen point.

The equations do predict massive yield cliffs at low Harmala/Salt concentrations, so that is something to keep in mind (see second 3D plot).

Again: these are first order equations that may not reflect behavior in the complex plant extract. Also, s was measured very crudely and may not be precise. With all those disclaimers in mind, we are just presenting what one could expect if the equations and the measurement of s are reasonable approximations.

Note: Edited on 12/9 to add more Teks and update plots

I've been having fun distilling off excess water. The harmalas stay dissolved with around 35-40% reduction in volume of the spent Manske solution. After the first reduction by 15-20% bumping becomes so violent it's time to stop the distillation and let things cool down. With slow cooling, some fairly large (5mm) NaCl crystals form.

The liquid is syphoned off and then a prayer of thanks is uttered for the removable lid of the flange flask Remaining liquid is removed using a Pasteur pipette as far as practicable and the NaCl is transferred to a storage container. Meanwhile, the once boiled solution is returned to the pot for a further reduction. A similar amount of distillate can be obtained as in the first round of distillation before excessively violent bumping starts to occur.

All the crops of NaCl crystals will be combined and dried with suction when the full ca. 2L have been reduced by 80%, or sooner if harmala HCl crystals become apparent on cooling of the supernatant to room temperature.

[In the absence of stirring capabilities, bumping can be lessened by using a vacuum pump to draw air through a narrow-bore dip tube which is placed with its tip near the bottom of the distillation flask. This results in a tiny amount of spray entrainment making its way through the distillation path and into the receiver, as detected by a faint fluorescence in a batch of distillate where this method was tested.]

Incidentally, the boiling temperature of NaCl saturated Mankse brine with ~1% acetic acid is 115°C. The spent Manske solution initially began boiling at 110°C. The vapour temperature at the still head was 98.5-99.5°C. The pH of the distillate was measured to be 3.5, using narrow-range pH papers.

In an effort to make this relevant (rather than a tangential thread-jack ) I'll post further results of this reprocessing in the coming days.