Sciencemadness Discussion Board

Extraction of palmitic, oleic etc. acids from olives oil

kazaa81 - 1-11-2004 at 14:11

Hallo to all,
does anyone know a procedure to extract fatty acids like oleic and palmitic from olive oil?

Thanks for help! ;)

Esplosivo - 1-11-2004 at 14:57

Oleic acid solidifies and precipitates from the oil at low temperatures. Just place the olive oil in the fridge, and after a while a white ppt will be present. This is a mixture of fatty acids which can be filtered out, mostly being oleic acid.

Thanks!

kazaa81 - 1-11-2004 at 15:05

Thanks very much,
Esplosivo, for the useful info.!

Ok, this is a method...
I was thinking to add 30% HCl to olive oil to get the acids from their salts in oil...probably I'm wrong......
Any idea about interchanges from acid-to-acid? Example...palmitic to caprylic (also sayed octanoic) etc.
Please maintain live this theard with any idea, not only ask-answer.

Thanx at all for help. :D

guy - 1-11-2004 at 15:36

Quote:

Oleic acid solidifies and precipitates from the oil at low temperatures. Just place the olive oil in the fridge, and after a while a white ppt will be present. This is a mixture of fatty acids which can be filtered out, mostly being oleic acid.


Will ths also leave behind pure glycerin?

neutrino - 1-11-2004 at 16:41

Vegetable oils are not made of simple acids. They are usually made mostly of mono-, di- and tri- glycerides (esters of glycerin and one, two, or three organic acid molecules, respectively) with small amounts of free acids. Cooling would probably not reduce the solubility of the free acids enough to get them out of solution. A hydrolysis reaction might, but then you’d have to somehow separate the glycerin and the acids, leaving enough water behind to hydrolysize the rest of the oil.
Quote:
Originally posted by kazaa81
I was thinking to add 30% HCl to olive oil to get the acids from their salts in oil...


You meant to add a base right? This would give you soap and glycerin, which could then probably be separated (I’m no expert in soap making, so I’m not sure how).

Mr. Wizard - 1-11-2004 at 17:23

Couldn't you make soap with the oil of your choice, by boiling it with an excess of Sodium Hydroxide? You then take the soap and allow it to separate from the water glycerine solution and then liberate the (stearic, palmitic, oleic ) acid by treating with a stronger acid, such as HCl or Sulfuric. This should be fairly easy to separate, as they are not very soluble in cold water. You might try a cheaper method of making the soap by using slaked masonry lime water and the vegetable oil, which leaves an insoluble calcium soap and a glycerine water solution. Calcium soap is usually an unwanted byproduct of hard water and forms an insoluble scum. Treatment of this calcium soap with Hydrochloric Acid might yield the desired oil acid and soluble calcium chloride, all with cheap materials.

If the lime and water doesn't make soap with the oil, you could first form a sodium hydroxide solution by mixing lime and sodium carbonate in water first, heating, and letting the calcium carbonate precipitate. Exclude CO2 from the air while letting it clear. Palm and Olive oils were used in the original PalmOlive Soap, and the reaction was supposed to be vigorous enough to not require external heating!

Most automotive greases are a mixture of a metallic soap and a mineral oil. For example, Lithium grease is a Lithium soap mixed with a mineral oil.

chemoleo - 1-11-2004 at 19:22

Yes, indeed, the best way to go about this is to boil your oil with a solution of NaOH, until the insoluble layer of oil disappears. You will then get the sodium salts of the respective fatty acids (called saponification). These may precipitate out, if they happen to be less soluble.
Of course you will also get glycerol (glycerin), which is of course soluble in H2O. No matter, you can then precipitate the acids with the correct amount of HCl. Their solubilities, and possibly melting points, should allow you to separate long-chain from short-chain acids, or unsaturated ones from saturated ones.
For instance, oleic acid is unsaturated, and due to Cis/Trans isomerisation on the double bonds and the lesser ability to 'crystallise' it has a lower melting point compared to the saturated fatty acid with the same number of carbons in the chain.

Best is to look up the respective ratios of fatty acids in different types of oils, and select the one that has the greatest proportion of the fatty acid of interest.

Esplosivo - 1-11-2004 at 23:12

Quote:
Originally posted by guy
Quote:

Oleic acid solidifies and precipitates from the oil at low temperatures. Just place the olive oil in the fridge, and after a while a white ppt will be present. This is a mixture of fatty acids which can be filtered out, mostly being oleic acid.


Will ths also leave behind pure glycerin?


I didn't mean that the oleic acid from the fatty acids will break up the ester bond when cooled and leave glycerine behind. I simply meant that a certain amount of oleic acid in the free state is present in olive oil, as far as I know. This can be seperated by cooling. The 'free' oleic acid dissolved in oil is somewhat in low concentrations though - must have slipped out of my mind :P

To extract most of the FAs an alkaline hydrolysis is preferred over an acid hydrolysis I suppose, so to extract 'insoluble' soap and leave a mixture of glycerine and the remaining alkali. Alkaline hydrolysis is usually carried out with NaOH though, and not with Ca(OH)2. The Ca salt of the FA would be highly insoluble in water (usually known as scum, left about by the reaction of soap with Ca salts in the water), ideal for seperation.

Hermes_Trismegistus - 2-11-2004 at 12:30

Quote:
Originally posted by Esplosivo
Oleic acid solidifies and precipitates from the oil at low temperatures. Just place the olive oil in the fridge, and after a while a white ppt will be present. This is a mixture of fatty acids which can be filtered out, mostly being oleic acid.


Explosivo is right (from personal experience) however "solidify" and "precipitate" are extremely loose terms.

Olive oil in the fridger results in pale green, cloudy, oily emulsion with a viscous consistency like the semen of a egyption mummy, thick, green and gooey.

Some kind of crude centrifugation followed by decanation off the top may help.

But no matter what method you use I don't relish the difficult task ahead.

I forsee several messy filtrations with mixed results. Perhaps salting the fats out would help some?

Its also gonna be an asspain like sitting on a meatfork to get your glassware squeaky clean and dry and as well as keeping your counter grease free.

I'd recommend putting down polyethylene backed butcher paper first, or even newspapers over waxed paper before going to work. I'd also keep the oven hot and the sink empty and wash my gear as I worked.

Saponification...ok!

kazaa81 - 6-11-2004 at 13:08

Hallo to all,

thanks very much to all who have maintained live this thread! Maintain live this one too.
I've heated the olive oil with NaOH for a while, 15 minutes, and I've get a thing like soap.
Now, because it is very tied to the beaker, I've fulled it with water and I'm waiting for the detaching of the soap-mass.
After this, how you've post, I dissolve this in strong HCl (would 30% suffice?) and then put the liquid (this is the first try) at 3-4°C (the oleic acid solidifing point) for see if the oleic acid, for first, would crystallize.

Thanx at all! Maintain live this thread!

[Edited on 7-11-2004 by kazaa81]

Experiments...

kazaa81 - 7-11-2004 at 14:14

Hallo to all,

I've saponified olive oil firstly with NaOH and today with Ca(OH)2.
The soap obtained from NaOH was put under water and then, removed water, added to 10% HCl until it was covered by HCl. Nothing seem to have dissolved.
Today, I saponified some oil with an excess Ca(OH)2.
After that, I've NOT put the soap under water, but I've taked some pieces of them and added to 30% HCl.
Bubbles has formed, due to the dissolving of residual Ca(OH)2 in HCl but, after 1hour, my soap seem to hasn't dissolved.
Must I wait other time? Tomorrow morning I will see.

Any idea, thing, attachment, sites and documents about fatty acids, saponification,experiments are welcomed.

Thanks for the collaboration. Maintain this theard live. ;) ;)

Mr. Wizard - 7-11-2004 at 19:01

Kazaa81, Have you heated the calcium soap with the acid to free the fatty acid? I'm not sure how fast this takes place, as it would depend on the solubility of the Calcium soap. It may not even work with calcium soap. Certain fatty acids, such as stearic acid, from beef tallow, are non too soluble themselves. You might have to try another solvent, or convert that oil with NaOH to a more soluble sodium soap, or use KOH and get 'soft soap', which is almost a liquid.

chemoleo - 7-11-2004 at 19:16

I don't understand the problem so much to be honest.
Just boil the oil with a stoichiometric amount (dilute!!!) of NaOH, until (after settling) there is no top layer of unreacted oil.
The sodium salts should be soluble, shouldnt they?
Then the addition of HCl should precipitiate the respective fatty acids, and the addition of calcium salts should precipiate the calcium salts.
Admittedly I don't know whether all sodium salts are soluble, I am sure there are some that aren't - but maybe that's a good way to start off.

Probably mistakes.....

kazaa81 - 9-11-2004 at 12:38

Hallo to all,

as previously writed, I've saponified my oil
with Ca(OH)2 until no oil appear.
I've put this Ca soap under 30% HCl for free the fatty acids combined in soap.
Well, after 1hour not one piece of this soap seem to have dissolved, I've saw only bubbles (I think of CO2 produced by unreacted Ca(OH)2).
Today, after 2 days of unwatched reaction, I've see that almost all pieces of soap (except one) have been dissolved.
I've added today some additional small drops of 30% HCl...hope that all the soap will dissolve!
For the crystallisation of oleic acid, which have solidifing point around 3-4°C, I think that the solution of acid/dissolved soap must be put in the fridge at the previously temperature.

Thanks to all for help! ;)

Twospoons - 2-3-2005 at 18:26

Quote:


OLEIC ACID, QsHaA, or C8HI7-CH:CH- [CH2]7 CO2 H, an organic acid occurring as a glyceride, triolein, in nearly all fats, and in many oilsolive, almond, cod-liver, &c. (see OILS). It appears as a by-product in the manufacture of candles. To prepare it olive oil is saponified with potash, and lead acetate added; the lead salts are separated, dried, and extracted with ether, which dissolves the lead oleate; the solution is then treated with hydrochloric acid, the lead chloride filtered off, the liquid concentrated, and finally distilled under diminished pressure. Oleic acid is a colorless, odourless solid, melting at 14 and boiling at 223 (10 mm.). On exposure it turns yellow, becoming rancid. Nitric acid oxidizes it to all the fatty acids from acetic to capric. Nitrous acid gives the isomeric elaidic acid, C8H17-CH:CH-(CH2]7-C02H, which is crystalline and melts at 51. Hydriodic acid reduces both oleic and elaidic acids to stearic acid.