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Author: Subject: Old bath oil is... fluorescent!
valeg96
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[*] posted on 20-4-2020 at 05:56
Old bath oil is... fluorescent!


Hello everyone! Just a quick photos of something unexpected: I was gifted a brand new bottle of mineral oil for heating baths, Merck, ca. late 1970s. Up until a few months ago it was still sealed and transparent, but it now turned to a black viscous mass, smelling of heavy diesel/tar, probably rich in PAH and... fluorescent!

Attached are some photos of this now useless thing: it's a shame I can't even pull something useful out of it. It will also be tedious to dispose of... unless someone with a private tugboat wants a liter of reagent-grade fuel? :D

The fluorescence is best seen under UVA-BLB 370 nm tubes. Other common tubes (UVA 352 nm and UVC 325.7 nm) reveal nothing.

Edit: As I expected, it won't burn on a simple alcohol lamp, but heating lowers its viscosity and heavy fumes rise, smelling of construction bitumen. Still, I'l keep a sample and dispose of the rest.

IMG_20200420_153159 (2).jpg - 927kB IMG_20200420_153356 (2).jpg - 558kB

[Edited on 20-4-2020 by valeg96]

[Edited on 20-4-2020 by valeg96]





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fusso
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[*] posted on 20-4-2020 at 06:07


No!!! Keep that fluorescent oil! You can extract the fluorescent compounds out!
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valeg96
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[*] posted on 20-4-2020 at 06:16


Well, I've thought about it already, and I wouldn't want to waste a shitload of solvents on that. Acetone kinda does the job, but again, there's no way to identify or purify them... Isn't it?




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fusso
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[*] posted on 20-4-2020 at 06:21


My guess is 75% iPrOH. Try it on a small scale to see if the extract fluoresce.

[Edited on 200420 by fusso]
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valeg96
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[*] posted on 20-4-2020 at 06:30


Left: Acetone. Right: iPrOH. Acetone is cheaper for me. I could extract them, distill the acetone, and repeat, assuming they won't break down on mild heating. Needless to say, petroleum ether just waters it down.

A couple drops of acetone ended up on my bench. The fluorescence is extremely intense, and yellow/green.

IMG_20200420_162623 (2).jpg - 674kB

[Edited on 20-4-2020 by valeg96]

[Edited on 20-4-2020 by valeg96]





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fusso
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[*] posted on 20-4-2020 at 07:25


Whats the colour of the solutions? Are they dark like the original?
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valeg96
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[*] posted on 20-4-2020 at 07:27


No, they are yellow. The thick oil is so packed with fluorescent molecules I fear it will be a really long project, should I embark in it. Also, heating the acetone solution over a flame does not destroy the fluorescent molecules.

Acetone is also much more efficient than iPrOH, at a glance.

Edit: The 5 mL of acetone I've used to very briefly treat the disrty plastic dish have already extracted enough fluorescent material to give a solid residue. Given the colossal amount in this liter of stuff, I'll definitely try it.

[Edited on 20-4-2020 by valeg96]

[Edited on 20-4-2020 by valeg96]





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mayko
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[*] posted on 20-4-2020 at 09:48


Neat! Do you have any chromatography supplies? Even a quick & dirty on a coffee filter might be interesting



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valeg96
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[*] posted on 21-4-2020 at 05:20


I have two packets of plastic TLC sheets 60 F254 (Merck 1.05750) but they are poorly revealed by my 4W tube (my other lamp is being repaired). I'll see what I can do.

The evaporated 5 mL left a yellowish residue, coated in oily traces, and further purification may be possible. It's fluorescent (yellow), but not as much as the solution.

IMG_20200421_151543 (2).jpg - 245kB





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nezza
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[*] posted on 29-4-2020 at 11:02


Most greases and oils are fluorescent. It's interesting to scan your oven and the area around it with a UV source to see just how much you miss when cleaning it.



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[*] posted on 29-4-2020 at 17:16


Why would the mineral oil have turned suddenly after all these years in a sealed bottle, do you think?
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valeg96
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[*] posted on 30-4-2020 at 03:02


I've attempted an extraction, but as I feared, it's an impossible feat. The extraction works way too well: once you shake it enough, the acetone extracts a lot of tarry brown residues as well, so I'd end up with a brown tarry, sticky mass and little to no hope of further purifications. As said, I'll just keep a sample and dispose of the rest.

Quote: Originally posted by nezza  
Most greases and oils are fluorescent. It's interesting to scan your oven and the area around it with a UV source to see just how much you miss when cleaning it.


Indeed. I've spilled a couple drops of the acetone extract and now my temporary bench is permanently fluorescent like a crime scene.





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[*] posted on 30-4-2020 at 06:49


Something that is brightly fluorescent probably doesn't contain much fluorescent material.


[Edited on 30-4-20 by unionised]
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valeg96
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[*] posted on 30-4-2020 at 07:05


I agree with that, but given the large amount of material and the bright fluorescence of the residue, I hoped I'd get out something. Unfortunately, as stated, way too much sludge dissolves in the acetone.




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[*] posted on 30-4-2020 at 13:41


I think IPA is more polar than acetone so less hydrocarbons will dissolve into it.
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[*] posted on 4-5-2020 at 07:41


G-Coupled. I suspect the oils become fluorescent as a reult of partial oxidation.



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[*] posted on 4-5-2020 at 08:18


Quote: Originally posted by nezza  
G-Coupled. I suspect the oils become fluorescent as a reult of partial oxidation.


Interesting, cheers. What manner of compounds would be formed thusly, I wonder? And why seemingly all of a sudden?

[Edited on 4-5-2020 by G-Coupled]
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