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The Fée Verte Absinthe Forum - The Oldest, Largest, Most Authoritative Absinthe Forum. > Absinthe & Absinthiana > Dr Magnan's Lab
Oxygenee
The article from the American Chemical Society journal referenced in this piece sound interesting:
http://blogs.timesunion.com/tablehopping/?p=1437

I'll try and obtain the original paper, and post at least an abstract on Thujone.Info (which, by the way, has a new logo).
Donnie Darko
You blinded me with science.
The Standard Deviant
When you mentioned a logo for thujone.info, I was expecting something more like this:

IPB Image
Hemingway's Hangover
"Creaming rate".

Heh. Is someone pulling a Beerbohm?
louched liver
Beer bong?

I'm pullin' my
Lil' SpedWad.
Shabba53
I would have liked to see that experiment take into account different speeds of water addition. i.e. power louche vs. regular louche.
dakini_painter
The abstract:

http://pubs.acs.org/cgi-bin/abstract.cgi/l…/la702186g.html

The full PDF can be reached through this link.

Absomphe
QUOTE(louched liver @ Feb 25 2008, 11:53 PM) *

I'm pullin' my
Lil' SpedWad.


As long as he doesn't ask any more stupid questions, in which case you misspelled 'crotch-punching'.

Oh wait, nevermind.
Steyr850
Slow Cream Coming.

IPB Image
Jaded Prole
The Green Fairy appears!
louched liver
Looks like a
stinging sea
nettle to me.
Absomphe
Better'n Jesus.

But you won't get as much for her on ebay.
louched liver
Mebbe Elvis?
Absomphe
Or Lennon.

Either way, on second glance, it does seem to resemble a crucifixion.
louched liver
Pope What's His Tits.
Steyr850
or Sigmund.

IPB Image

louched liver
Or Artemis.
Absomphe
That could explain his absence.
Steyr850
Nougat™

IPB Image
Head_prosthesis
Absinthiades©
sixela
QUOTE(Oxygenee @ Feb 25 2008, 10:32 PM) *

(which, by the way, has a new logo).

The things you can do with just a molecule of Oxygen…I bet it's not a coincidence and you thought "I'm the dot in .info" when you got that idea.


Helfrich
QUOTE(sixela @ Mar 4 2008, 10:16 PM) *

just a molecule of Oxygen…

Atom. One double bound oxygen atom.
louched liver
He thinks covalently big.
Donnie Darko
Is the science behind the louche really that mysterious?

trans-Anethole looks like this:
IPB Image

It's seriously hydrophobic, i.e. not very water-soluble. It has no Hydroxyl or Carboxyl group on the end of it, and those two functional groups are usually what makes molecules hydrophilic (i.e. water soluble). Ethanol DOES have a Hydroxyl group on its one end making it water soluble (i.e Hydrophilic), meanwhile the proton on its other end makes Anethole soluble in Ethanol. When you add water to something that is hydrophobic, what happens? It runs away from the water, more technically the bond between C2H6O and C10H12O isn't as attractive as the bond between H2O and C2H6O, so the Ethanol and Water run off together thanks to Ethanol's sexy Hydroxyl group, and Anethole can't stand the H2O so it runs away jilted, and decides it's better being a loner. Something about Anethole (I have no idea what) makes it resistant to penetration by photons when it is clustered together, and so it reflects light when it forms globules, thus giving the "white" louche effect.

Is there anything more to it than that? I'm no chemist so somebody please correct me if I've got it wrong.

As a side note, I wonder if this is why some people say some absinthes taste like "hay":
http://www.rsc.org/Publishing/ChemScience/…eeping_ouzo.asp
speedle
Hmmm…it's apparently not exactly that simple.

Science of the Louche

I think that study is available directly, but somewhere else I can't recall now.

Oh, wait, that turns out to be the same damn study! Well, see, I knew it was somewhere else.

Donnie Darko
OK, maybe I oversimplified it. It's an interesting experiment, but where is the control? And what happens if you add H20 to anethole only, omitting ethanol? As far as I can tell all of their solutions are water/ethanol/anethole, so they're not really answering what H20 does to anethole all by itself, which might illuminate what happens when it's a water/anethole/ethanol mixture.
hartsmar
A couple of years ago I found a Swedish paper on this, I'll see if I can dig that up...
Donnie Darko
I think the stability of the emulsion that seems to baffle the authors of the article is simply due to hydrogen bonding between anethole molecules pushed together into clusters by water because of their hydrophobic nature. It's worth noting the Louche effect occurs strongest at cold temperatures, and hydrogen bonds do happen more readily and are stronger when the molecules are moving slowly (cold temperatures slows down molecular motion). The O in the Anethole is inclined to be negatively charged, and may attract one of those H protons hanging off the other end of the molecule, thus forming a loose latticework of hydrogen bonds between Anethole molecules with a hydrophobic periphery (sort of like a membrane) that results in the "globules" and reflects or diffracts light. I noticed in their experiment that all solvents were at room temperature, whereas I think if they also did them at 5c then they might discover more about the stability of the emulsion.

In my opinion the possible Hydrogen bonding between Anethole molecules is sufficient to explain the stability of an anethole/ethanol/water emulsion without having to invoke any LSW theory or Ostwalt ripening equations, which as far as I can tell don't exactly fit their experiment, and don't take into consideration the possibility of hydrogen bonds affecting the outcome.

Of course this is just me speculating with no experimental data to back up anything I've said, but I think it's a plausible hypothesis, though maybe that's just because I don't understand the Ostwald ripening effect or LSW theory or whatever they call it very well.
density
I read the article with some interest about a month back, and may be able to help out some.

Donnie, your first big post (#25) is all fine and great, but not really the aim of the article. They take for granted that people understand that the anethole will come out of solution when water is added, and are not probing that. A different experiment might probe the levels of anethole vs. water vs ethanol required for a good louche (but this would probably just give the czechs the lowest amount of essential oil of anise to add to their bitter to gain a louche. Cost effective, low on that horrible anise flavor, and we would have to admit that their product contained anise and louched! I’ll not run that experiment!)

The aim of the experiment is to determine why the liquid remains turbid for so long, that is, why the little droplets of anethole don’t all glom together quickly and float to the top of your drink. (Remember, don’t add ice to your ouzo or you’ll get an oily film on top!)

To probe this they used two instruments. First they used a light scattering instrument to check the size of the anethole droplets. They found the droplets to be very very small, and the size to grow very slowly. (the light scattering instrument works by shining laser light through a thin mixture and gathering the scattered light. By comparing the pattern of the scattered light to reference patterns the instrument can give you a good guess at the size of the things scattering the light in the liquid (I would say particles, but we’re talking about a liquid at present). Oh, and while I’m at it, that’s probably why the louche is white, the oil droplets are just scattering light. And there are a quadzillion of them in there. The light gets tossed around a whole lot, refracted from here to there to back to your eyes. Comes out white.

Ok, fine, but they have another neat tool. Enter Oswald and a gnoll. Using their second instrument they were able to measure the interfacial tension of the anethole in the ethanol-water solution. They ran into some problems here as the anethole was partially soluble in the water ethanol mixture, but they were able to get some results. The instrument watches the size and shape of a drop of anethole suspended by a syringe inside a cuvette of water/ethanol solution. They had to saturate the water/ethanol solution with anethole first, though. And did a couple dirty tricks to try to get results.

In the end of the day, the experimental results are that the more water you add the more stable your louche. The empirical results are just the opposite, more ethanol equals more stable louche. So… they screwed up somewhere. (I think I know where, and would do the experiment a bit differently, were I them). But the cool, take home part, is that the anethole has a very low surface tension, which means the oil droplets glom together less readily (think oil and vinegar and how quickly the oil will all come together). Since they glom slowly, you end up with a fairly stable mixture of ethanol/water and oil droplets. If the anethole had a high surface tension (well, it would be more likely to mix with the water, but…) it would come together, right now and you wouldn’t want to drink it.

Oh, and sorry, I suck hardcore and the short answer section of any test. This is the concise version. You want more, I’ll ramble on about high speed cameras and bubble methods and Owen Wendt approaches and Du Nouy rings and disperse vs. polar vs. acid vs. basic components and how the world would be a swell place if Zisman plots worked for everything.

density
Dirty Double Post
condensed version:

They only wanted to know why an absinthe stays cloudy and drinkable for a long time and why the anethole doesn't all glom up and make a nasty scum in your drink. The reason is that it has a low surface tension.

now back to creaming things
Donnie Darko
Thanks for illuminating that, it's pretty obvious my chemistry knowledge is pretty rudimentary compared to the experimenters. The way you describe it makes a lot more sense and I see what they're talking about a lot more. I'm kind of surprised at their surprise that adding ethanol decreased the louche though.

Anethole is repelled by water, causing it to clump together and louche (but not so much that it completely separates from the water solvent, which is the focus of their study), and Anethole is attracted to ethanol, so it seems pretty friggin obvious that making ethanol the main solvent will reduce the louche, which would obviously compel the anethole to form less globules since it would be busy running towards the ethanol to bond with it instead of sticking to itself to get away from the water.
density
I don't believe they said that the ethanol decreased the louche, but that the ethanol increased the stability of the louche. That only makes sense, in adding water more anethole is forced out of solution and Le Chatelier suggests that as the concentration of suspended (not solubolized) anethole increases the rate at which the anethole will glom together will increase. At some point the anethole droplets increase in size to such a point that the louche is gone and you end up with a oily residue on the top of your (nolonger)absinthe. Think of when the oil and vinegar separate out, anethole on top and (un)absinthe below.

The researchers understood this, and expected to see this reflected in their results. But the instrumental conclusion is the opposite, which implies a flaw in their measurements. In the conclusion of the paper they state that the instrumental data was not verified by observations. They screwed up.
Donnie Darko
Out of curiosity, where do you think they went wrong?

This is the red flag for me: " In our calculations, we have assumed that the diffusion of the oil is constant and is independent of the composition of the medium."

That being said, just because their measurements don't fit the expected results doesn't mean they screwed up, especially since, as they point out, "expected results" are based on theories developed based on two-component, not the 3 component system they're working with.
Le Gimp
Not only that, but 'good science' is always open to investigation of why an experiment behaved differently than was expected rather than redefining the experiment to get the results you want.
density
I agree with both of you, but, Le Gimp, they did neither nor. My comment that they screwed up is to say that their calculations did not match their observations, and they didn’t sufficiently explain why.

I believe a good explanation of the stability of the louche might come from more theoretical rather than experimental study. We know the surface tensions of the liquids, if we do not know the dispersive/polar and acid/base components, that would need be found. Then, a lot of math happens.

I’m not ready to do the work right now, but with the time, money and effort I believe it possible. If I had been accepted into school A instead of school B, I would have tried to propose some of this research. Unfortunately, school B does less work similar to this, and while I could probably do the work at my current job… there is no way I could get this project past the gates.

So, in conclusion, you’re right. Screwed up is a little harsh, but I just meant to say that they did not measure what they were trying to, and did not sufficiently explain the difference. But if they’re doing this type of work right now, there is a good chance that this was just paper number 1 of more to come!
Donnie Darko
Yeah, it seems to be relatively uncharted territory, so it's no surprise that one of the few published studies on this matter has some holes in it.

I couldn't even begin to do the math associated with this, I'm just starting to study college level chemistry and am getting tutoring to get caught up on the math end of it, but conceptually speaking, I do think their assumption that the diffusion of the oil is constant is unwarranted, and since they based their calculations on that assumption then that could upend everything. It seems like there would be some push/pull effect on the Anethole between the ethanol/H20 mixture that would mess up a constant diffusion across the concentration gradient.
Provenance
QUOTE(Le Gimp @ Jun 6 2008, 06:51 AM) *
'good science' is always open to investigation of why an experiment behaved differently than was expected rather than redefining the experiment to get the results you want.


There are more direct ways of stating that you don't work for the government.

Donnie Darko
Ha! Thank goodness the current Government method of "throw out all data that doesn't validate your hypothesis" never caught on in actual science.
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