[kbarb]

I might be in the wrong forum but this seems like an organic molecule based question, albeit not a Phd exam question exactly.

Someone left a 5 gallon jerry can of what looks like cooking oil behind a fence on our property - probably used, but it looks clear w/ cooking oil color.
I thought to take it to the nearby biofuels processor, but I can't guarantee them it's not something petroleum based.

Is there any way to tell if it's vegetable based or petroleum based ?
I don't have access to anything like spectroscopy or similar.

Otherwise I'll have to take it to hazardous waste, which is much farther away. It would be nice if it could be recycled though.

Thanks if anyone has an idea,

Kent

[Arkcon]

You can probably tell them apart by the smell.  New cooking oil and petroleum oils do smell, slightly different.  And if slightly used, cooking oil smells more like food, and engine oil smells more like metal.  Besides, I think the local biodiesel co-op can use mineral oil, even used, for something  And probably have the means to test it in some way.  They ought to just take it of your hands.  Its not like you rolled in 10 separate 50 gal drums.

[Archer]

Cooking oil is saponifiable, try refluxing a millilitre with dilute  sodium hydroxide for three hours.

If It's cooking oil you should have a relatively clear solution.

[kbarb]

Ah, good idea.
Basically I want to try to make soap out of it, right ?

[curiouscat]

A trick might be to look for one of those additives people spike refined petroleum products with : MTBE / ETBE / ethanol / TEL (no longer) / some sort of lube additive etc.

Other heavy metals, mercaptans etc. are also more likely in crude derived products.

Though not sure if an easy procedure exists to qualitatively spot test any of 'em.

[Enthalpy]

Vegetable oil is denser.

[curiouscat]

Vegetable oil is denser.

That's a good easy way. But I don't think he's sure it's only a oil.

If you expand to wider petro based organics, I don't think the density fact holds.

[Archer]

Ah, good idea.
Basically I want to try to make soap out of it, right ?

Yes, if you make it dilute enough then you should be able to separate the saponifiable from non-saponifiabe if it is a mixture of pertroleum and oil.

[kbarb]

I'll try to saponify it in the next couple of days when I get a moment.
It's been a million years since I took chemistry classes so I'm down to looking up "How to make soap" for the proportions.
I just have some liquid Drano around, and all the recipes call for powdered lye.

Anyway, I just smelled it again, and it really doesn't have any kind of organic vegetable oil aroma to it.
Actually a faint "paint thinner-ish" sort of smell.
It's very clear and very yellow though, like corn oil.

For what it's worth, I held a match up to it - and right on it -  and couldn't get it to light at all.

So I'll try the saponification method.

Thanks very much for all the suggestions !

-Kent

[Archer]

You will want considerably more of the caustic solution than you would use in soap making to prevent, as far as possible, any petroleum (which may or may not be present) becoming solubilised by the detergent that formed by saponification of fatty triglycerides.

[kbarb]

Ok, I tried, and I got no saponification at all.

I heated both the mystery oil and some liquid Drano to about 90°, then poured the Drano into the oil while stirring.
I should get at least some kind of fairly thick soap, right ?

I just get some kind of incomplete mixing of oil & lye (and water I think, as it's liquid Drano), but about the same viscosity and color as the original oil.
Eventually it separates completely into the two parts.

[Btw, can you add too much lye and ruin the experiment ? I kept adding lye until about 2:1, lye:oil, just to see what would happen, and still no soap.]

Anyway I don't think it's vegetable oil : although it looks like it, it really doesn't have the expected smell anyway.

Unless anyone thinks otherwise, I think I'll take it to hazardous waste - probably why someone abandoned it in the first place.

[kbarb]

Oh, and thanks everyone for all your help and advice.
People on this forum are extraordinarily helpful - you get some really creative and thoughtful responses.
Maybe I should have stayed in the world of chemistry, as I did well in it in the university many years ago.

Kent

[Archer]

Ok, I tried, and I got no saponification at all.

I heated both the mystery oil and some liquid Drano to about 90°, then poured the Drano into the oil while stirring.
I should get at least some kind of fairly thick soap, right ?

I just get some kind of incomplete mixing of oil & lye (and water I think, as it's liquid Drano), but about the same viscosity and color as the original oil.
Eventually it separates completely into the two parts.

[Btw, can you add too much lye and ruin the experiment ? I kept adding lye until about 2:1, lye:oil, just to see what would happen, and still no soap.]

Anyway I don't think it's vegetable oil : although it looks like it, it really doesn't have the expected smell anyway.

Unless anyone thinks otherwise, I think I'll take it to hazardous waste - probably why someone abandoned it in the first place.

I would expect some reaction to occur under those conditions, if it separates on standing then it is non-saponifiable in my opinion.

Without specialist equipment I don't know what else you can do to test this to prove that it isn't "hazardous waste".