Sciencemadness Discussion Board - Cleaning carbon dust from the bottom of a flask

Cleaning carbon dust from the bottom of a flask

agorot - 1-6-2010 at 07:28

Hey everyone

I made some KClO3 the other day with carbon electrodes. To make a long story short, I now have some very fine carbon particles at the bottom of a 500 mL RBF that my fingers can't reach, nor can a paper towel. It obviously won't dissolve in water. Anyone have any ideas on how to clean it out? It's just settled to the bottom over a long period of time and it won't come out.

not_important - 1-6-2010 at 07:50

A flask cleaning brush?

Try putting some water, a drop of detergent, and a bit of course sand into the flask, and swirling it for awhile.

woelen - 1-6-2010 at 09:04

Another option is to put some coarse sand and water in the flask and then shake.

The WiZard is In - 1-6-2010 at 11:53

Quote: Originally posted by agorot

Hey everyone

I made some KClO3 the other day with carbon electrodes. To make a long story short, I now have some very fine carbon particles at the bottom of a 500 mL RBF that my fingers can't reach, nor can a paper towel. It obviously won't dissolve in water. Anyone have any ideas on how to clean it out? It's just settled to the bottom over a long period of time and it won't come out.

-----------
Nitric acid perhaps. Or oxidize it into graphic acid. Details in
among others — Mellor's 16-volume opus. 5:828 &ff

Heat it with some of your chlorate and report back.

[Edited on 1-6-2010 by The WiZard is In]

hissingnoise - 1-6-2010 at 12:06

Quote:

Heat it with some of your chlorate and report back.

Report! Yeah!
But if you want to go technical, get one of your artists hogshair brushes and scrub the inverted flask so that the residue falls out. . .

zed - 2-6-2010 at 06:45

Turn the flask upside down. Create a static charge on the flask. A Van DeGraff generator should do that nicely. Provided there is no adhesive material present, the flask and the carbon particles, both bearing the same charge, will repel each other.

Shazzam. The particles will fall off, and out of the flask. Maybe.

Another possibility, involves heating the flask fairly hot over a bunsen burner, and sweeping the bottom of the flask with a stream of pure oxygen. The carbon particles will be oxidized to CO2, and you will be spared the labor of scrubbing.

kmno4 - 2-6-2010 at 09:15

Recently I had similar problem (residue after PS pyrolysis).
And one more time, warm H2SO4+K2Cr2O7 (or any chromate, CrO3...) mixture did not disappoint me.
In case of C particles, oxidation may take a few hours but always works.

rrkss - 2-6-2010 at 09:58

Quote: Originally posted by kmno4

Recently I had similar problem (residue after PS pyrolysis).
And one more time, warm H2SO4+K2Cr2O7 (or any chromate, CrO3...) mixture did not disappoint me.
In case of C particles, oxidation may take a few hours but always works.

Chromic acid is toxic, carcinogenic, pain in the ass to dispose of legally and not needed for most cases. Why not start with something mild like scrubbing with a brush, and a mild nonscratching abrasive soap. If that does not work, a soak in a solution of KOH + Ethanol usually does the trick.

[Edited on 6-2-10 by rrkss]

agorot - 2-6-2010 at 13:30

you guys are terrible

and don't you think I would have already tried a brush?
I'll see how the sand works.

kmno4 - 2-6-2010 at 22:28

Quote: Originally posted by rrkss

Quote: Originally posted by kmno4

Chromic acid is toxic, carcinogenic, pain in the ass to dispose of legally and not needed for most cases.

As far as I know non-carcinogenic is only water and air.
Other substances are or will be recognized as carcinogenes.
Chromic mixture has been well known and used for many years. It is cheap and easy to prepare. Its purpose are mainly carbonaceous impurities.
It can be a pain in the ass only in if used rectally.....

psychokinetic - 3-6-2010 at 00:07

With a spoon.

And a lot of violence.

mr.crow - 3-6-2010 at 07:50

Piranha solution

Maybe you can neutralize your waste chromic acid with alcohol (carefully!) so you get Cr3+

Cr free cleaners use sodium persulfate and H2SO4. You can get ammonuium persulfate for etching circuit boards. I'm not sure if this is effective.

zed - 3-6-2010 at 17:13

Ozone?

Mr. Wizard - 3-6-2010 at 17:45

Use a slow flow of O2 into the flask and start warming the spots with carbon on them, with a flame from a Bunsen burner This will work unless the dark material you think is carbon, is something else.

Jimmymajesty - 8-6-2010 at 12:05

A Van DeGraff generator... Dude.. you can not be serious about that!

Just heat the flask with cc H2SO4, It always worked for me to remove carbon particles, char, tar etc.. from everything (except from porous surfaces like Al2O3) chromium compounds are not necessary, and I second that their use is a PITA

Lambda-Eyde - 8-6-2010 at 14:02

Quote: Originally posted by woelen

Another option is to put some coarse sand and water in the flask and then shake.

I second this! I had a 250 ml round bottom flask with quite a lot of tar in it that would not go away. I tried to clean it with HNO<sub>3</sub>, then NaOH. Neither was effective. I didn't have any brushes that would reach the tar, so brushing was out of the question.
However, adding some coarse marble (calcium carbonate), a few drops of detergent and shaking made it shine like never before.

not_important - 8-6-2010 at 15:59

Actually you're thirding it, I suggested that in my first reply, as well as using a drop of detergent along with the sand and water as that seems to help wet condensed organic films clinging to glass in my experience.

Still, a few good flask brushes are worthwhile investments.

For thicker deposits, refluxing a cheap high boiling organic solvent such as kerosene can help, I've used it after cracking polystyrene. After refluxing the solvent for awhile pour the still hot solvent off, repeat if needed. Finish with some more conventional cleaning route - brush or sand.

puppycock - 23-11-2010 at 09:36

I suggest using piranha solution, I left an organic solution drying unattended for too long and decomposed leaving a bunch of elemental carbon stuck to my round flask and it was perfectly clean after 5 minutos of heating.