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Quince
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Which extraction method to use for plants
There seem to be many extraction methods for essential oils, and I don't know which one to choose. Is there any advantage to doing steam distillation
over solvent extraction? This far I've used methylene chloride in a first extraction, then alcohol to separate the oils from the waxy extract.
However, I find that there is a characteristic smell left regardless of what types of plants I extract, which is the same with some commercial
extracts I've tried, so I can't help but wonder if the methylene chloride reacts with something, or the 80*C reached when evaporating the alcohol is
too much (I guess I could evaporate it under vacuum, if the landlady is away or I'd get killed for the water usage). I can't do supercritical CO2
since I don't have the equipment. Does anyone here have experience with different methods and can make a recommendation? I've been thinking of
trying the steam distillation, but I want to ask first if there's any advantage. I also read about "controlled instantaneous decompression" as an
extraction method, but didn't find much detailed information with Google, other than what's in this abstract.
BTW when extracting with alcohol from the waxy first extract by DCM, is it OK to use methanol or propanol instead of the commonly specified ethanol?
Ethanol is harder for me to obtain in high concentration.
[Edited on 7-12-2006 by Quince]
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unionised
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It rather depends what you are extracting and why.
Extraction with DCM is great for things that are not thermally stable but, unlike steam distillation, it takes all the waxes and fats too.
Ethanol has one huge advantage if you are making extracts to use as food additives or pharmaceuticals- it's essentially non toxic. *
Methanol and IPA have fairly similar solvent properties; if you are trying to get rid of waxes I'd go for methanol unless your product is unusually
non-polar. Methanol is easier to evaporate off afterwards but IPA is usually thought of as less toxic.
*Yes, I know, ethanol is responsible for more cases of poisoning than just about any other chemical
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Quince
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What I'm trying to extract is essential oils. Some for the smell (vanilla and a ton of others), some for other stuff (for example, nepatalactone is a
good non-toxic mosquito repellent, and I can get plenty of free catnip).
Do you think the DCM or alcohol could be reacting with something in the plants? I always find that the results of such solvent extraction have an
additional smell to them I don't like, and like I said in the first post, I've found this in some commercial extracts as well. Or perhaps it's
extracting some component that other methods do not...
Now would steam distillation in this case necessarily need the steam to be at 100*C? I don't know much about the process so I'm not sure about this.
I know that water vapor doesn't condense right away when it's cooler than that.
I take it you haven't heard about that "controlled instantaneous decompression" extraction? They steam the material for a few minutes, then instantly
drop the pressure near zero, and claim it gets 90-97% of the oils. Since I could only access the abstract, I still didn't understand how they
physically separate the oils from the plant material afterwards. Just squeezing it out perhaps?
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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XxDaTxX
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| Quote: | Originally posted by Quince
What I'm trying to extract is essential oils. Some for the smell (vanilla and a ton of others), some for other stuff (for example, nepatalactone is a
good non-toxic mosquito repellent, and I can get plenty of free catnip).
Do you think the DCM or alcohol could be reacting with something in the plants? I always find that the results of such solvent extraction have an
additional smell to them I don't like, and like I said in the first post, I've found this in some commercial extracts as well. Or perhaps it's
extracting some component that other methods do not...
Now would steam distillation in this case necessarily need the steam to be at 100*C? I don't know much about the process so I'm not sure about this.
I know that water vapor doesn't condense right away when it's cooler than that.
I take it you haven't heard about that "controlled instantaneous decompression" extraction? They steam the material for a few minutes, then instantly
drop the pressure near zero, and claim it gets 90-97% of the oils. Since I could only access the abstract, I still didn't understand how they
physically separate the oils from the plant material afterwards. Just squeezing it out perhaps? |
Its use is limited to specific industrial processes. It is not feasible for either of the following adaptations:
1. When done in a batch process, ie all at once, you would probably need something around the order of 20,000L of volume to hold your 800mL of DCM
(assuming a final temp of ~-70C) w/o pulling DCM into your vacuum. You'd need a pump that could pull 10mbar, and a vessel that can handle the extreme
pressure and temperature drop to get good efficiency.
2. A modified version exists where this can be adapted to a semi-continuous process, however you would need a cryogen to condense the vapor @10bar.
I'm sure you have a LN2 tap somewhere ..... oh yes here it is! =P
On a side note, do your essential oil extractions like everyone else. There is a reason why only industrial extractions vary from this procedure:
steam distill, partition with DCM, filter organic phase, dry, heat/distill off DCM and you can get back to whatever it was that you were going to do
with the essential oil...
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Quince
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The reason I skip steam distilling is because by extracting directly with DCM I don't expose the material to high temperature. I also need a minimum
amount of DCM, whatever's needed to reach high enough level in the Gregar, which is a continuous extractor. I'm not sure what the point of the steam
distillation is, and that's in fact part of my initial question. Why is steam distillation used, instead of using an organic solvent from the
beginning?
| Quote: | | heat/distill off DCM and you can get back to whatever it was that you were going to do with the essential oil. |
As unionised mentioned, that also extracts waxes, so alcohol extraction is still needed.
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pantone159
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| Quote: | Originally posted by Quince
The reason I skip steam distilling is because by extracting directly with DCM I don't expose the material to high temperature. Why is steam
distillation used, instead of using an organic solvent from the beginning?
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With steam distillation, you don't expose the material to temps over 100 C, so that also counts as low temperature a lot of the time.
With a straight extraction, without the steam distillation, you may also pick up non-volatile compounds, which you usually don't want.
One example from my experience: I have tried extracting eugenol from cloves, both with solvent extraction (I used alcohol and then let it evap before
continuing), and with steam distillation. In both cases, the crude extracts were separated via an acid/base extration using DCM/NaOH/HCl. (This is a
common lab experiment.)
With steam distillation, I got fairly pure eugenol, only lightly yellow-brown colored. With solvent extraction, I got a much darker colored product,
which was obviously not pure. Apparently, cloves contain some non-volatile colored component which follows phenols around in the extractions. (High
MW polymerized phenols???). Steam distillation left the brown junk behind, solvent extraction picked it up.
It does depend on your plant. Some things work well with solvent extraction, some don't.
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Quince
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I guess then the question is when does it not work.
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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XxDaTxX
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| Quote: | Originally posted by Quince
The reason I skip steam distilling is because by extracting directly with DCM I don't expose the material to high temperature. I also need a minimum
amount of DCM, whatever's needed to reach high enough level in the Gregar, which is a continuous extractor. I'm not sure what the point of the steam
distillation is, and that's in fact part of my initial question. Why is steam distillation used, instead of using an organic solvent from the
beginning?
| Quote: | | heat/distill off DCM and you can get back to whatever it was that you were going to do with the essential oil. |
As unionised mentioned, that also extracts waxes, so alcohol extraction is still needed. |
If you are extracting essential oils you use water to steam it out. Honestly, I don't quite know what will persuade you to do it right. If you want
the nitty gritty here you go:
1. DCM dissolves wax as a function of its temperature, at higher temperatures it dissolves more and more wax, and is thus carried over any
distillation head.
2. The amount of wax able to dissolve in DCM / oC s not 1:1. Its a higher order function.
3. Water counters the effect that DCM has on the solubility of the wax. By adding water, it interacts with what used to be just DCM:wax so now you
have DCM:wax:water. Changing the composition in the still changes the composition of the vapor thus produced in favor of DCM (due to high relative
volatility) and against wax (due to insolubility in water, polarity).
4. Just do it and stop arguing. DCM is a prime defatting/dewaxing solvent at higher temperatures. Particularly because a quick temperature swing and
solubility goes down, where after it is recovered by centrifuging, and STEAM DISTILLATION, or hot air volatilizing and scrubbing. We use it in
industrial applications ALL THE TIME.
5. If you want essential oils, use water. For tincture/organic solvent extraction use alcohol. And for WAX, USE DCM.
[Edited on 9-12-2006 by XxDaTxX]
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unionised
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"DCM dissolves wax as a function of its temperature, at higher temperatures it dissolves more and more wax, and is thus carried over any distillation
head."
What, exactly, does solubillity have to do with distilation?
Water disolves salt as a function of temperature; at higher temperatures it disolves more and more salt.
Nevertheless, salt gets left behind when seawater is distilled to produce fresh water.
I still want to know what this weird wax is- it is very odd that it distills along with DCM.
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XxDaTxX
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| Quote: | Originally posted by unionised
"DCM dissolves wax as a function of its temperature, at higher temperatures it dissolves more and more wax, and is thus carried over any distillation
head."
What, exactly, does solubillity have to do with distilation?
Water disolves salt as a function of temperature; at higher temperatures it disolves more and more salt.
Nevertheless, salt gets left behind when seawater is distilled to produce fresh water.
I still want to know what this weird wax is- it is very odd that it distills along with DCM. |
It is not odd. It is predictable. The high solubility in high temperatures has to do with their molecular interactions. Those same interactions
govern, somewhat, the vapor pressures of the constituents in in your still.
DCM is used to remove waxes from lubricant oils ALL THE TIME, so again NO IT IS NOT ODD that it comes over with DCM. Send it to an analytical lab and
they will tell you what it is. Is it worth your $ to know? Probably not. And similarly, it is no longer worth my time trying to persuade people in
this thread to do things right.
[Edited on 10-12-2006 by XxDaTxX]
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unionised
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It wouldn't be very $ for me to get a lab to analyse it; I work in one. Of course, since I don't have a sample of it, I can't analyse it. I have
analyse plenty of things in my time, some of them waxes.
For the wax to distill at 40C it needs to have a reasonable vapour pressure at 40C. Very few solids do.
As I said, salt dissolves perfectly well in water, but it doesn't distill.
It's news to me that DCM is used to dewax oils (and Google doesn't give any hits about it for "dewaxing oil" dichloromethane).
Last time I checked lube oil mixed freely with DCM. If you chilled it well enough you might get the wax out, but any solvent could be used for that.
It still has nothing to do with the idea that a wax would distill at 40C
[Edited on 10-12-2006 by unionised]
[Edited on 10-12-2006 by unionised]
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XxDaTxX
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| Quote: | Originally posted by unionised
It wouldn't be very $ for me to get a lab to analyse it; I work in one. Of course, since I don't have a sample of it, I can't analyse it. I have
analyse plenty of things in my time, some of them waxes.
For the wax to distill at 40C it needs to have a reasonable vapour pressure at 40C. Very few solids do.
As I said, salt dissolves perfectly well in water, but it doesn't distill.
It's news to me that DCM is used to dewax oils (and Google doesn't give any hits about it for "dewaxing oil" dichloromethane).
Last time I checked lube oil mixed freely with DCM. If you chilled it well enough you might get the wax out, but any solvent could be used for that.
It still has nothing to do with the idea that a wax would distill at 40C
[Edited on 10-12-2006 by unionised]
[Edited on 10-12-2006 by unionised] |
If you work in a lab then ask your teacher.
Read some books on Raoult's Law as it governs (somewhat) the composition of your distillate.
Here is an intro.
Now if you have understood that then model a vapor pressure diagram for DCM, your wax, and water. (It should have three axes)
Due to specific interactions between DCM and the wax (as can be seen from the temperature dependant solubility) you have a non-ideal mixture.
Adjusting for positive deviations for the wax's vapor pressure, and negative deviations for DCM's vapor pressure, redraw your vapor pressure diagram.
Remember that mol fraction of in the lower phase is severely limited by its solubility, but it does affect it significantly.
I will not tell you how to compute the actual deviations because one can devote a complete post-doc career in it, however I will tell you that it gets
more and more complex.
What you have from there is a rough estimate of how water changes vapor pressures. Deviations can be calculated within the framework of a particular
model, each having specific applications of non-ideal mixtures.
Congratulations, you have now seen what happens ...... IN THE LOWER PHASE ONLY!
..... Read a book if you want to see what goes on in biphasic equilibrium. Google is not the place to look. Try industrial chemistry literature.
Here's a reference on using DCM to dewax oils.
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unionised
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My teachers may well be retired if not dead by now, it's been a couple of decades or so since I left University. I actually work in a real analytical
lab.
I'm well enough aquainteed with Raoult's law to know that it refers to the vapour pressures of the components of the mixture- I trust that you are
too.
The point that you have been steadfastly ignoring is that, unless the vapour pressure of a component is reasonably high, it never gets into the vapour
phase (to any significant extent) so it doesn't distill over.
What I am asking is "what is this wax with a high vapour pressure at 40C? because most solids don't have high vapour pressures."
Do you understand that the rarity of volatile (at 40C) waxy solids makes this stuff a real oddity?
Most solids, like the salt in seawater, don't distill with steam and they are even less likely to do so with DCM vapour at 40C.
It's interesting to note that the reference you give for dewaxing with DCM points out that a whole slew of other solvents can be used (as I sugested)
and also, that by steam strippping or distillation, the DCM can be recovered from the wax. They point out explicitly that distillation separates wax
from DCM. I'm saying it's odd that in the case we have been discussing the wax distills over with the DCM and that I would have expected the
distillation to separate them because the difference in boiling poinst between very volatile DCM and (usually very involatile ) wax is huge.
You seem to think it's perfectly normal for these two components to co-distill. I don't and nor does the reference you cite.
[Edited on 11-12-2006 by unionised]
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Quince
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Well, next time I get a can I'll check the company and post the name here, so anyone interested can contact them for an MSDS, which should list the
mystery ingredient.
My own feeling is that, though the head temperature did not exceed 40*C, the flask most certainly did, and not all the wax vapors condensed in the
Vigreux, but some got through (after the steam distillation mentioned in the other thread, about 5%).
[Edited on 11-12-2006 by Quince]
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XxDaTxX
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| Quote: | Originally posted by unionised
My teachers may well be retired if not dead by now, it's been a couple of decades or so since I left University. I actually work in a real analytical
lab.
I'm well enough aquainteed with Raoult's law to know that it refers to the vapour pressures of the components of the mixture- I trust that you are
too.
The point that you have been steadfastly ignoring is that, unless the vapour pressure of a component is reasonably high, it never gets into the vapour
phase (to any significant extent) so it doesn't distill over.
What I am asking is "what is this wax with a high vapour pressure at 40C? because most solids don't have high vapour pressures."
Do you understand that the rarity of volatile (at 40C) waxy solids makes this stuff a real oddity?
Most solids, like the salt in seawater, don't distill with steam and they are even less likely to do so with DCM vapour at 40C.
It's interesting to note that the reference you give for dewaxing with DCM points out that a whole slew of other solvents can be used (as I sugested)
and also, that by steam strippping or distillation, the DCM can be recovered from the wax. They point out explicitly that distillation separates wax
from DCM. I'm saying it's odd that in the case we have been discussing the wax distills over with the DCM and that I would have expected the
distillation to separate them because the difference in boiling poinst between very volatile DCM and (usually very involatile ) wax is huge.
You seem to think it's perfectly normal for these two components to co-distill. I don't and nor does the reference you cite.
[Edited on 11-12-2006 by unionised] |
I already explained that it was non-ideal and the wax has a positive deviation from raoult's predicted vapor pressure.
If you want the theory behind it, thats more simple:
Let's assume that intermolecular forces between wax molecules in a pure liquid is some value "x" ... then assume that the intermolecular forces for
DCM in a pure liquid is some value "y".
Then when you mix them, BECAUSE THEY ARE SUBSTANTIALLY DIFFERENT like I said before, they become non-ideal.
Intermolecular forces between DCM and the wax are less than DCM : DCM or wax : wax interactions.
In this way you can see that because the intermolecular attraction between the two components decreases upon mixing, their respective vapor pressure
also changes because they are less "bound" to the liquid phase due to lowering of intermolecular attractive forces.
The reason for the water is two fold: first it should produce a compensating negative deviation for the wax, while having little to no effect on the
polar DCM.
Your salt and water example is one of negative deviations. The intermolecular forces set up in the mixture, ionic, increase the amount of energy
needed to vaporize its components. In this way it is non-ideal as a negative deviant of Roult's law.
Interactions between components create non ideal mixtures, and corresponding non ideal vapor pressures.
BTW, I certainly hope that someone in your "real analytical lab" knows more than the introductory material on Raoult's law. Positive and negative
deviations are the first thing explained past the undergraduate courses in chemistry ... and I would hate to know that there is an analytical lab run
by undergrads .... oh wait .... thats like what I have to deal with .... back to scolding these undergrads.
[Edited on 11-12-2006 by XxDaTxX]
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solo
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Reference Information
An original solvent free microwave extraction of essential oils from spices
Marie Elisabeth Lucchesi, Farid Chemat,* and Jacqueline Smadja
FLAVOUR AND FRAGRANCE JOURNAL Flavour Fragr. J. 2004; 19: 134–138
ABSTRACT:
Attention is drawn to the development of a new and green alternative technique for the extraction of essential oils from spices. Solvent-free
microwave extraction (SFME) is a combination of dry distillation and microwave heating without added any solvent or water. SFME and hydrodistillation
(HD) were compared for the extraction of essential oil from three spices: ajowan (Carum ajowan, Apiaceae), cumin (Cuminum cyminum,
Umbelliferae), star anise (Illicium anisatum, Illiciaceae). Better results have been obtained with the proposed method in terms of rapidity (1 h vs. 8
h), efficiency and no solvent used. Furthermore, the SFME procedure yielded essential oils that could be analysed directly without any preliminary
clean-up or solvent exchange steps.
KEY WORDS: solvent-free; microwave; dry distillation; essential oil; ajowan (Carum ajowan); cumin (Cuminum cyminum); star anise (Illicium
anisatum)
[Edited on 11-12-2006 by solo]
Attachment: An original solvent free microwave extraction of essential oils from spices .pdf (103kB)
This file has been downloaded 1558 times
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solo
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Reference Information
Kinetics of Isothermal and Microwave Extraction of Essential Oil Constituents of Peppermint Leaves into Several Solvent Systems
Michael Spiro and Sau Soon Chen
FLAVOUR AND FRAGRANCE JOURNAL, VOL. 10, 259-272 (1995)
Abstract
The rates and extents of extraction have been measured for three major constituents of peppermint oil, namely l,&cineole, menthone and menthol,
using the leaves of the black mint (Menthu X piperitu L.). The solvents used
were hexane, ethanol and mixtures of composition 90mol% ethanol + 10mol% hexane and 90mol% hexane + 10mol% ethanol. The extractions were carried out
isothermally at 25, 35 and 45°C as well as in an electrically
and mechanically modified domestic microwave oven where the temperature increase vaned from c. 10 to 30°C.
The rates of both isothermal and microwave extractions were sensitive to the solvent employed and decreased in the order 90mol% hexane > 90mol%
ethanol > hexane > ethanol. The rates of microwave extraction were also
affected by the microwave power output and the size of the sample load. The activation energies for the extractions were in the range 30-90kJ mol-',
again dependent on the solvent used. Scanning electron microscopy on the spent leaves provided evidence of a link between the kinetics of extraction
and structural changes on the glands.
KEY WORDS Extraction kinetics; microwave extraction; solvent extraction; rate constants; essential oils; peltate glands; peppermint (Mentha x
piperita L.); 1,8-cineole; menthone; menthol; dielectric properties
Attachment: Kinetics of Isothermal and Microwave Extraction of Essential Oil Constituents of Peppermint Leaves into Several Solvent (1.1MB)
This file has been downloaded 815 times
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unionised
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XxDaTxX
I guess that you are used to dealing with undergrads- you have my sympathy on that matter. Perhaps that's why you aren't used to dealing with someone
who is sufficiently familiar with Raoult's law and deviations from it that he doesn't need to quote chapter and verse on it.
DCM and water form an azeotrope. Raoult's law predicts that no azeotropes exist.
Clearly, there are deviations from it, I already knew that. You can rest assured that someone in my lab knows about it; I do. (Incidentaly, I also
know that distilation isn't used much in analytical labs these days so it wouldn't be the end of the earth if nobody knew about Raoult's law. In
addition many, if not most mixtures don't know about it anyway, they certainly don't follow it)
Simply stating that "I already explained that it was non-ideal and the wax has a positive deviation from raoult's predicted vapor pressure." doesn't
really help unless you can tell me what sort of thing has this great a deviation.
The most volatile solid I could find the data for in a quick search was camphor; I estimate that it has a vapour pressure of a couple of mmHg at 40C.
At that temperature DCM has a vapour pressure of roughly 760mmHg. If they started off equimolar then the mixture coming over, if it followed Raoults
law, would be something like 0.3% camphor (the usual crass aproximations have been made here).
What you are talking about is a deviation from Raoult's law of an order of magnitude or 2. As far as I'm aware, that sort of thing doesn't happen
unless something really weird is going on.
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XxDaTxX
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| Quote: | Originally posted by unionised
XxDaTxX
I guess that you are used to dealing with undergrads- you have my sympathy on that matter. Perhaps that's why you aren't used to dealing with someone
who is sufficiently familiar with Raoult's law and deviations from it that he doesn't need to quote chapter and verse on it.
DCM and water form an azeotrope. Raoult's law predicts that no azeotropes exist.
Clearly, there are deviations from it, I already knew that. You can rest assured that someone in my lab knows about it; I do. (Incidentaly, I also
know that distilation isn't used much in analytical labs these days so it wouldn't be the end of the earth if nobody knew about Raoult's law. In
addition many, if not most mixtures don't know about it anyway, they certainly don't follow it)
Simply stating that "I already explained that it was non-ideal and the wax has a positive deviation from raoult's predicted vapor pressure." doesn't
really help unless you can tell me what sort of thing has this great a deviation.
The most volatile solid I could find the data for in a quick search was camphor; I estimate that it has a vapour pressure of a couple of mmHg at 40C.
At that temperature DCM has a vapour pressure of roughly 760mmHg. If they started off equimolar then the mixture coming over, if it followed Raoults
law, would be something like 0.3% camphor (the usual crass aproximations have been made here).
What you are talking about is a deviation from Raoult's law of an order of magnitude or 2. As far as I'm aware, that sort of thing doesn't happen
unless something really weird is going on. |
What I already explained is the theory behind what he is seeing. I don't know how else to explain it, but that is how it works. If you look at phase
diagrams for non-ideal mixtures you will see severe changes when intermolecular forces change sharply between pure liquids and their respective
multicomponent mixtures..... after all, what else do you think is holding them in the liquid phase, but those intermolecular forces and the pressure
above them?
There are few examples better at explaining this phenomena than dipole-dipole DCM and London Dispersion Wax .... being combined to lose those
interactions, thus making it easier to leave the liquid phase. The fact that it affects the wax's vapor pressure more than the DCM has to do with the
fact that LD is a weak force to begin with, destroy that and what else is a wax to do but vaporize.
[Edited on 11-12-2006 by XxDaTxX]
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Quince
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Thinking back to the extraction of HNO3 with DCM, the patent claims that the two form a bond of sorts. Is something analogous possible with the wax?
That is, not just a simple solution of the wax into the DCM?
Also, I want to stress again that, although the head remained at 40*C, the flask was much hotter. That not all the wax vapors condensed in the
Vigreux could have been simply because I was distilling too fast.
A final question: if I get another batch of paint stripper, should I just do the steam distillation, or do I need regular distillation first to remove
other things such as the methanol?
[Edited on 11-12-2006 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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unionised
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Those weak forces are normally enough to keep it together at 40C unless it's a wax that boils below 40C in which case I really want to know what it
is.
There are 3 sets of forces to consider you have missed out the dipole- induced dipole force ie between DCM and wax. This is generally stronger than
the London force. If the wax can be melted without boiling then the relatively weak London forces are sufficient to keep the stuff in the liquid phase
rather than the vapour. The forces holding it back in solution rather than vapourising ie the induced dipole interactions are stronger so the
deviation ought to be negative. Similarly, the relatively strong dipole dipole interactions in pure DCM are destroyed because the wax molecules get in
the way. If anything this means that the DCM should be easier to distill out than Raout's law would suggest. (of course, this is offset- the DCM is
less strongly held to the wax, but the wax is heavier so there is some chance of the DCM escaping as a dimer but little chance of a wax+DCM molecule
doing so).
Anyway, if your point holds for wax and DCM it will also hold for "oily fatty crap" +DCM so you cannot evaporate DCM from oily stuff to recover it.
More interestingly, it would also hold for "the stuff I just synthesised in any of a whole bunch of practical experiments and the extracted into
ether". That means I cannot extract my product into ether and then evaporate off the ether to collect my product.
This is news to me, and, I suspect, to many others on this site.
(BTW, if you want to refer to this post please don't quote the whole lot- doing so just takes up more storage space and bandwidth)
[Edited on 11-12-2006 by unionised]
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Maya
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Why don't we put down the nice theoretical discussions and simply find out what the heck you got in the wax?
You know ? some simple organic micro-qualitative testing for functionality?
my god that would be so easy and tell you exactly how to purify....
I learned that first year organic chem , its easy....
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Quince
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Well look who's here... the Hindu creator of the universe!
Not possible for me, for the simple reason that I never took chemistry in university. Indeed, my specialty couldn't be further from it.
[Edited on 11-12-2006 by Quince]
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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Maya
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yes but you ARE dealing with chemistry, you have to try and understand some of the principles involved otherwise you'll be beating your head on the
wall, and ours on the internet, everytime that you don't understand something.
really, it is very easy. DUDE, this is the first page I got when i googled "organic qualitative analysis" and it looks like a good one out of
many...........
http://chemserv.bc.edu/ugrad/lab/org/QualAnal.pdf
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Quince
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| Quote: | Originally posted by Maya
beating your head on the wall, and ours on the internet |
If so, I'm amazed neither head nor wall has broken this far...
\"One of the surest signs of Conrad\'s genius is that women dislike his books.\" --George Orwell
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