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Full Version: Mercury Vacuum Still -- Gimmick?
The Fée Verte Absinthe Forum - The Oldest, Largest, Most Authoritative Absinthe Forum. > Absinthe & Absinthiana > Dr Magnan's Lab
Provenance
http://greenhookgin.com/process.html
Tibro
Lab vacuum apparati often use oil. Their application is generally designed for stills accommodating a few liters. A vacuum apparaatus meant to accommodate a 300 liter still may/could well use mercury, I suppose. I'd be curious to know more details of the set up.
L'Assommoir
Here is a whole line of low-temp/pressure booze, including an absinthe.

http://www.masterofmalt.com/distilleries/p…randed-spirits/

Tibro
Where does it say vacuum distillation is used for all those samples? More importantly, where do they have info about their vacuum distillation equipment and the process they employ?
L'Assommoir
It looks like I read that wrong.
only the absinthe is rotovap, I guess.

so for the absinthe:
http://www.masterofmalt.com/Blog/post/Cold…d-Absinthe.aspx
Tibro
Rotovap? I'm not so sure. In any case, it doesn't look like they're anywhere close to 300 liters.
Provenance
QUOTE(Tibro @ Sep 7 2012, 12:30 PM) *
A vacuum apparaatus meant to accommodate a 300 liter still may/could well use mercury

They should use it to make Mad As A Hatter Absinthe.
Tibro
Or Dead as a Doornail Absinth advocating the flaming boh_mian method.
Artemis
The Greenhook page is nothing but bad advertising copy. There's no such thing as a "mercury vacuum still". A column of mercury (a metal in liquid phase) was originally used to measure atmospheric pressure. It's roughly 30 inches high at normal pressure. It's shorter at lower pressures. These days an analog or digital gauge is used. Note the picture of the analog gauge that goes from zero to thirty on that same page.

The bath for a rotary evaporator could be water or oil. The bigger the boil vessel, the bigger the bath, but three liters is big for a table top evaporator.

The pictures on the masterofmalt page show a (relatively) cheap evaporator, although I can't be 100% sure it's rotary because I don't see the motor.

An evaporator isn't strictly speaking a still, although it makes use of the same physical principles of evaporation and condensation. An evaporator doesn't have to be rotary, and introducing a vacuum (reduced internal system pressure) into a still could be done with an ordinary pot still.

What the rotation does is provide a thin layer of liquid on the upper surface of the rotating boil flask that more readily changes phase to vapor than the surface of the boiling stuff in the rest of the flask. Think of an even film of water on the windshield of your car versus the surface of a lake in a storm. Since the flask is constantly rotating, that calm quiet layer of consistent thickness is continuously made available to the system for phase change.

Twenty liters would be a very big rotary evaporator. I think those exist, but 300 liters? I don't think so. The motor needed to spin that thing would power a Corvair.
Tibro
QUOTE
An evaporator isn't strictly speaking a still, although it makes use of the same physical principles of evaporation and condensation.

The technical difference(s) being what, if I may ask?
Artemis
An evaporator is designed to evaporate solvent from a substance in the boil flask with the intent of "cleaning" (for lack of any better word that comes to mind) and then retrieving said substance. The solvent which is evaporated as vapor and then condensed back to liquid is discarded (or maybe recycled for further use, I don't know). When you use it to make an herbal liquor, such as absinthe, it's a sort of backasswards use. The solvents (ethanol and water) carrying the scent molecules are retained after condensation as distillate and it's the stuff left in the boil flask that is discarded. So the difference between an evaporator used for its designed function and used as a still is a matter of from which end of the apparatus you retrieve the good stuff, so to speak. But since it works like a still, it could be called a still.
Tibro
Semantics, me thinks.

Functionally in both cases, conventional still vs. evaporator, you put a mixture of fluids which you wish to separate and with the purpose of collecting a desired fraction in purified form. Whether the desired fraction is left in the pot or whether it comes over as the collected condensate seems irrelevant to me. The process is the same. You are separating a mixture according to boiling points. Boiling point being a crude term, but generally understandable and not misleading, for what the process is doing. In layman's terms they're not really different at all, as far as the end result of collecting a desired liquid in a purified state compared to the messy admixture you start with.
Artemis
QUOTE
Whether the desired fraction is left in the pot or whether it comes over as the collected condensate seems irrelevant to me.

Except that if the "desired fraction" is a solid, you're not going to find it at the collection end of the process. The intent is entirely relevant to the selection of the device to be used for the process (still vs. evaporator).
QUOTE
In layman's terms they're not really different at all, as far as the end result of collecting a desired liquid in a purified state compared to the messy admixture you start with.

See above. The desired part is liquid in the case of absinthe, but that's not necessarily so with other things that are purified by evaporation, in which case the solvent is only a tool and not what's being sought as a final product.
It's not semantics, it's calling a spade a spade. Sometimes you can get a spade's work done with a hoe, but that don't make it so, ya know?
Tibro
If I want to separate dirt from river mud I should use a vacuum still?

Semantics, yes. I can evaporate the liquid by laying the muck on the shore and letting the atmosphere do the work.

But aren't vacuum stills used to obtain those oh so desirable hydrocarbon fuels we're all so dependent on? The fractions of which come across at different points and which we use, not the sludge left behind.
Artemis
QUOTE
If I want to separate dirt from river mud I should use a vacuum still?

No, you should use a rotary evaporator.
QUOTE
I can evaporate the liquid by laying the muck on the shore and letting the atmosphere do the work.

And the wind and the waves and the seagulls will also do their work. Depends upon whether seagull shit and washed-up condoms are desired in your your dirt, I guess.
QUOTE
But aren't vacuum stills used to obtain those oh so desirable hydrocarbon fuels we're all so dependent on?

I don't know, but the vacuum is irrelevant in the discussion of evaporator vs. still for dedicated purposes.
thegreenimp
QUOTE(Tibro @ Sep 8 2012, 03:47 PM) *
But aren't vacuum stills used to obtain those oh so desirable hydrocarbon fuels we're all so dependent on? The fractions of which come across at different points and which we use, not the sludge left behind.


A fractionating tower is a wee bit different, from my days of modeling refineries.
Provenance
QUOTE(Artemis @ Sep 8 2012, 12:28 PM) *
Sometimes you can get a spade's work done with a hoe, but that don't make it so, ya know?

Angelfood was no hoe.
Tibro
QUOTE
The intent is entirely relevant to the selection of the device to be used for the process (still vs. evaporator).

And yet an evaporator can be used to obtain the same results that one can achieve using a still. Without modification and without damage to the apparatus. I imagine same goes for using a still to do the work of an evaporator. If the two are functionally interchangeable then what's the difference?

A spade and a hoe are not interchangeable. On the other hand, if I consider a spade and a shovel then I begin to see the difference.
Artemis
QUOTE
I imagine same goes for using a still to do the work of an evaporator.

That's the nice thing about imagination, you can take it anywhere and don't even have to dress it up.
Tibro
But even with a good imagination it still's better with hand cream.
R3al Caravano
Yes, Mercury is a measure of vacuum as I am sure is said. Any vacuum apparatus of size does not use oil; this is reserved to little piss ass lab units. The general question remains why would you use vacuum to distill something with an azeotrope (especially with a high relativity difference between the items that azeotrope)? In this there lies no advantage in either an energy or a degradation standpoint. (You might as well use benzene like they did in the 50s.) If any of you money fuckers have not figured this out as of yet: the Pressure, Temperature, Concentration (alcohol to water ratio) is set by physics. There is 2 degrees of freedom ie you set two of the three said conditions the other is set by the natural laws governing our universe (physics). This means if you have a given concentration of booze to water in your pot at a given time and you work at a set pressure the the temperature is not under your control. (This was well documented before any of your grandparents were born.) To make the story short if you want more essential oil: increase the water content in the pot and/or increase the pressure.

This shit is getting boring.
G&C
Just like instant jello…
Artemis
QUOTE
The general question remains why would you use vacuum to distill something with an azeotrope (especially with a high relativity difference between the items that azeotrope)?

The fact that ethanol and water form an azeotrope has nothing to do with the reason for using the vacuum. The vacuum is used to lower the boiling point of the solvent containing the essential oils. The implications of extracting essential oils from plant material without heating them much above room temperature are obvious. Or should be.
QUOTE
In this there lies no advantage in either an energy or a degradation standpoint.

You're wrong. Avoiding degradation caused by heat is precisely the advantage.
QUOTE
the Pressure, Temperature, Concentration (alcohol to water ratio) is set by physics.

No, the ethanol to water ratio is set by the distiller when making absinthe. Without a vacuum, he has no control over the pressure in the system, and thus, none over the boiling point of said ethanol/water mixture. With a vacuum, he has that control.
QUOTE
This means if you have a given concentration of booze to water in your pot at a given time and you work at a set pressure the the temperature is not under your control.

If by "the temperature" you mean the boiling point of the mixture in the still, this is true with an ordinary still. But with a vacuum still, the boiling point of the mixture in the still is entirely under your control due to your control of the pressure in the system. This is the whole point.
QUOTE
To make the story short if you want more essential oil: increase the water content in the pot and/or increase the pressure.

Increasing the pressure will at some point mean no vaporization. That's why pressurized water reactors contain water at 650 degrees F with no boiling. Getting back to a still, no oils can be extracted at all with no vaporization, and increasing the pressure would require a greater input of heat to drive vaporization, so I don't see why you would want to increase the pressure. In any case, vacuum distillation has to do with the QUALITY of the oil, not the quantity.
QUOTE
This shit is getting boring.

Boring is bad, but wrong is worse.
Donnie Darko
Haven't had time to log in in many moons, but everything Artemis said is true.
Provenance
Yo, D-Squared, you stayin' dry?
G&C
Didn't he just post that he was getting drunk?
Tibro
Inundated wuz what it sounded like.
Provenance
QUOTE(Donnie Darko @ Oct 28 2012, 02:17 PM) *
everything Artemis said is true.

You're right, he's drunk.
Jaded Prole
And you?
Donnie Darko
QUOTE(Provenance @ Oct 29 2012, 10:15 AM) *

Yo, D-Squared, you stayin' dry?

Well luckily I don't live in the neighborhood that's under water now, so yeah, all is well in Brooklyn.
Sadly the liquor I've had the last two nights has been the first opportunity to do so in months. I really need to pick the habit back up, I hear it's good for your cholesterol.
Grim
And your DayZ gameplay skills… glad to see you fared well(-enough), Donnie.
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