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Author: Subject: steam distillation with one or two vessels
Cloner
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[*] posted on 16-10-2010 at 11:46
steam distillation with one or two vessels


There are two ways you can use to steam distill oils from solid material. You can heat the oil containing substance in water, or lead (overheated) steam through it.

My question is why the second procedure gives a way better yield. The only way I could achieve any separation in layers of distillate at all, getting essential oil from myrrh resin, was to heat a saturated salt solution, leading the overheated steam through the solid.

I could not obtain any yield of oils from orange peel powder by just heating it directly with water, either.

My theory is that getting oil from solids is somehow accelerated by contact with steam while it's staying where it is when just heating it with water. Anyone have true understanding of this topic?

[Edited on 16-10-2010 by Cloner]
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Magpie
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[*] posted on 16-10-2010 at 16:57


Quote: Originally posted by Cloner  

My question is why the second procedure gives a way better yield. The only way I could achieve any separation in layers of distillate at all, getting essential oil from myrrh resin, was to heat a saturated salt solution, leading the overheated steam through the solid.

I could not obtain any yield of oils from orange peel powder by just heating it directly with water, either.
[Edited on 16-10-2010 by Cloner]


First of all I want to congratulate you on a clever way to produce superheated steam. I did some calculations using a Kb for water of 0.512C/molality. Using a saturated salt solution would raise the bp 7C. Using a 50% NaOH solution would raise the bp 25.6C! But I would check the steam condensate pH before using any NaOH method.

I don't have a "true" understanding for why indirect steam is best but I suspect it all has to do with the temperature being higher, especialy if the steam is superheated. One of my organic texts says that the direct method can have problems if solids have settled on the bottom of the flask, ie, bumping, etc. Indirect steam keeps those pretty well stirred up.




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kclo4
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[*] posted on 16-10-2010 at 20:25


Calcium chloride solutions can get a very high boiling point.

Are you talking about having the orange pills in the boiling water?
If so, I believe it is their is simply more heat in the steam at 100*C than there is in the water at 100*C and so it more effectivly extracts it. In all honesty though, I don't really understand it but that is what I have always understood it to be - and I believe I got this idea from another post on here, so doing some searching around might reveal a better explanation.
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spirocycle
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[*] posted on 17-10-2010 at 17:00


well if the steam is superheated, it is hotter, obviously

the higher the temperature, the hotter the herbs can get
the hotter the herbs, the more volatile the oils
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Cloner
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[*] posted on 25-10-2010 at 09:59


The 7 degrees difference don't really raise the % of essential oil in the vapour phase by that much. The difference between barely any yield and an oil layer that separates is not merited by a few degrees. The mixture of essential oils and water has a lower vapour pressure than both components separately. The molar fraction in the vapour phase is determined by the vapour pressure at that temperature.

In any case, I am still struggling to get a proper yield of orange oil. Steam distillation of a mixture of liquids is much simpler than a distillation of oil from solids in suspension. All I can think of to improve is to use a high mesh sieve and regrind the material until it is really pulverized.
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