Hi I made dioxane from ethylene glycol and sulfuric acid in June and distilled it once and kept the distillate.
Last week I distilled it a second time and when the distillation was over much gunk remained in the flask; I added sulfuric acid to dissolve this
gunk. The gunk did not dissolve so I heated it in a far away outside fireplace ; it did not dissolve but the contents overflowed.
Now the gunk is stuck to the flask; is it possible to dissolve it in concentrated NaOH or would another method be better.
BromicAcid - 23-10-2016 at 10:12
Ehhh, what a mess. I would go mechanical removal before trying with 'solvents' again, likely you just have carbonized junk which will not dissolve in
much of anything. I would be reluctant to use Piranha on it since you likely have plenty of more readily oxidizeable garbage in there which can lead
to problems. What size is the flask, it's hard to tell. A wooden doll rod is a good place to start because if you slip you likely will not punch a
hole in your flask.dactyl - 23-10-2016 at 10:14
If you dig most of the char out with a spatula or something then swirl the copper beads round they scour out quite a lot more.
You will probably end up using something like boiling H2SO4 to get the last of the junk out. dactyl - 23-10-2016 at 11:56
Would boiling the junk with H2SO4 turn it into carbon dioxide? What about piranha?unionised - 23-10-2016 at 12:49
At a high enough temperature
C + 2 H2SO4 --> CO2 +2SO2+ 2 H2O
(at that temperature you are pretty near the point where C + O2 --> CO2 and also near the pint where the glass melts)
Piranha works toodactyl - 23-10-2016 at 12:52
sulfuric acid would be a gas most likely at atmospheric pressureBromicAcid - 23-10-2016 at 16:11
Instead of copper balls I have used rock salt and methanol to shake around in flasks to abrade the gunk off the walls.AJKOER - 24-10-2016 at 05:07
Apply physical methods.
Then, run a much less physical and more advanced photochemical or Fenton reaction to produce hydroxyl radicals in the presence of hydrogen gas (best
under pressure) to attack the carbon. Place in sunlight and let it sit for some time.
Logic: Both the hydroxyl radical and the hydrogen atom radical (from the action of the hydroxyl radical on H2) attack carbon.
Sample embodiment: Place a very small amount of Zinc metal in a large excess of cheap HCl or H2SO4 together with sheets or bars of Iron and Copper.
Seal after venting out air to form a pressurized hydrogen atmosphere. Place in sunlight.
-------------------------------
Another idea, not as gaseous but full of juice. Make an electrode with say a stainless steel ball soldered on to an insulated copper wire. The other
electrode is copper that is positioned in the middle of the flask. Rest the ball/electrode on the carbon surface and move it around as needed during
an electrolysis (using a battery source) of an electrolyte of, say, aqueous MgSO4. My experience with graphite is that is it just falls apart in the
process of making CuSO4 and a white precipitate of Mg(OH)2.
[Edited on 24-10-2016 by AJKOER]woelen - 24-10-2016 at 09:56
K2Cr2O7 (or CrO3) with concentrated H2SO4 and then heating this in the flask. This dissolves many difficult to remove organic/carbonized compounds. It
is more toxic than piranha solution, but much safer to use, because there is no risk of explosion.
Piranha solution is much better from an environmental point of view. You can mitigate the waste issue somewhat by dissolving the orange
acid/hexavalent chromium mix in water and adding sodium metabisulfite until the color is purely green with a bluish hue. If that point is reached you
have trivalent chromium. You can flush that down the drain with a lot of water.dactyl - 2-12-2016 at 21:16
Thanks for the replies.
I would have responded much sooner but I got stuck with work and later sick.
The dissolution in piranha acid seem slow to a degree when I added it. A majority of the product I suspect is carbon since I dont believe piranha
oxidized elemental carbon well.DraconicAcid - 3-12-2016 at 00:51
If I have carbonized gunk in a flask, I usually put a bit of nitric acid in it, and hit it with a bunsen burner.CuReUS - 3-12-2016 at 05:25
I bet some copper coated metal BB's would work just as well, and you could probably pick them up at the closest big store.DFliyerz - 6-12-2016 at 08:43
I think Praixchys used acetone in one of his videos to clean it.Amos - 6-12-2016 at 09:36
I'll second Woelen's idea. Chromic acid is very effective at getting rid of nasty organic residues, not just by reacting but by physically detaching
them from the flask. And while you're at it you may as well reduce the leftover hexavalent chromium with some ethanol and add sodium carbonate to
precipitate chromium(III) hydroxide which is fun to have around.Chlorine - 6-12-2016 at 09:50
I personally use store bought copper coated steel BB's. Swirl them around the flask with 10=15 mls of water then use a strong magnet to get them out
of the carbon water solution.Herr Haber - 7-12-2016 at 04:58
I'm not terribly good at maths but...
H2SO4 + H2O2 (or K2Cr2O7) + danger involved and time spent in cleaning = more than than what I'd pay for a new RBF dactyl - 12-2-2017 at 18:42
@CuReUS
The concentration was 15%; this likely was one of my issues.
Attachment: ja01450a002.pdf (472kB) This file has been downloaded 378 times
dactyl - 12-2-2017 at 18:45
ignore the attachmentPraxichys - 13-2-2017 at 06:29
Anything strongly oxidizing in combination with sulfuric acid and strong heating should work. You can try dichromates, permanganates, H2O2, nitrates,
and persulfates. Always use these mixtures with extreme caution. Certain organic materials form explosive mixtures with these strong oxidizers.Amos - 13-2-2017 at 07:26
Hot NaOH solution seems to be very good, not at dissolving this kind of gunk, but physically detaching it from the glass surface. I often do this and
then use a sharp tool to kind of break up the stuff so that it can fit through the glass joints out of the flask.
