weiming1998
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Extraction of liquid fatty acids from vegetable oil
Recently, I have tried to extract liquid fatty acids from vegetable oil. Here's what I used:
1, Sodium hydroxide is added to some vegetable oil, which neutralizes the fatty acids and forms a soapy substance.
This substance is not that soluble in water (less than table salt),
So I placed the chunks in a sodium bisulfate solution, with excess bisulfate. There was sizzling noises, probably from the unreacted NaOH reacting
with the acid. After a day, I got this strange oil-like substance that is transparent. So I flitered out the substance. But the strange thing was that
it was miscible with water! Attempts to separate the layers with both potassium permanganate and copper sulfate failed. The first one lost its colour
quickly and the second one just made an evenly dispersed, very light blue solution (much lighter than copper sulfate and pure water.)
The question is, why are the triglycerides in the fatty acid soluble in water? Even if I managed to separate the carboxylic acid from the glycerol,
then it still wouldn't be soluble, because, as far as I know, longer chained organics (be it alcohols or carboxylic acids) are insoluble and will form
two layers.
Does anyone have a clue what happened?
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UnintentionalChaos
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1) read up on making soap. Simply stirring with NaOH won't cleave the glyceryl esters. You need to warm the mix and to be done in any reasonable
length of time, you need to heat it once the initial exotherm (which is slow in the making) slows down. Once you're done, chuck it in acid. The fatty
acid layer floats.
2) Vegetable oil has unsaturation. KMnO4 will oxidatively cleave these.
3) copper soaps are insoluble
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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bahamuth
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Quote: Originally posted by weiming1998  | | After a day, I got this strange oil-like substance that is transparent. So I flitered out the substance. But the strange thing was that it was
miscible with water! |
This is very possibly glycerol...
Usually if you want a reasonable yield of free fatty acids you will need to do the saponification in a suitable solvent.
Now, I am not a fatty acid separation expert but why would you use KMnO4 or CuSO4 to try to separate anything, was this an attempt to "salt" the fatty
acids out?
Any sufficiently advanced technology is indistinguishable from magic.
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weiming1998
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| Quote: Originally posted by bahamuth | | Quote: Originally posted by weiming1998 | | After a day, I got this strange oil-like substance that is transparent. So I flitered out the substance. But the strange thing was that it was
miscible with water! |
This is very possibly glycerol...
Usually if you want a reasonable yield of free fatty acids you will need to do the saponification in a suitable solvent.
Now, I am not a fatty acid separation expert but why would you use KMnO4 or CuSO4 to try to separate anything, was this an attempt to "salt" the fatty
acids out? |
No. it was an attempt to separate the layers, if both layers are transparent, then it would be hard to see the two layers. So I add something in that
would colour the water blue, but the fatty acid would remain transparent, or a much lighter blue. But that hasn't happened.
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weiming1998
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| Quote: Originally posted by UnintentionalChaos | 1) read up on making soap. Simply stirring with NaOH won't cleave the glyceryl esters. You need to warm the mix and to be done in any reasonable
length of time, you need to heat it once the initial exotherm (which is slow in the making) slows down. Once you're done, chuck it in acid. The fatty
acid layer floats.
2) Vegetable oil has unsaturation. KMnO4 will oxidatively cleave these.
3) copper soaps are insoluble |
1) Yes, I will try your advice.
2) Maybe that's why the water changed from the purple colour back to transparent again.
3, I did not try and make a copper soap, I was making a sodium soap, then acidified the solution, and then added in copper sulfate to colour the water
but not the acid.
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