[Saarith]

A visoucsity glassware I have got filled with soot when a couple of my students decided to measure the viscousity of used motor oil.

Can anyone here tell me a way to clean the soot in this apparatus without damaging it.

http://imgur.com/IL428iv

Any help would be appreciated.

[Arkcon]

This is going to be a tough one, we have to clean your glassware, but because its meant to be a precision instrument, we can't be as vigorous as we need to be.

Some thoughts:

Try washing as thoroughly as possible with lab soap and water.  You probably have, but try again.  See if you can gradually get the charred material out.   Its worth a try.

Try a sonicator with soap and water, maybe a solvent to reduce surface tension.  See if something comes out.  If so, then just keep doing that until its clear enough.

Maybe concentrated sulfuric acid will attack enough of the organic component of the soot and get most of the char out.  It's unlikely the soot is pure carbon.

If this weren't a precision instrument, I'd suggest scouring powder.  Maybe concentrated base will attack the glass enough to let everything was free.  However, these options will likely attack the bore, and alter calibration. So you'd have to re-calibrate.  Perhaps you have to do that often, or even after the gentler methods above to be sure, so it may be something you try anyway.

[Saarith]

I tried the base already but it didn't have any effect.

I haven't tried concentrated sulfuric acid. Will have a go at that tomorrow.

I sort of assume I will have to recalibrate it after cleaning or at the least test the calibration.

Thanks for those ideas.

[DrCMS]

I would throw it away and buy a new one they are only $75-150 each new (depending if you get it calibrated or not) and I doubt you'll ever get it clean; particularly the fine capillary part that is so important to the viscosity measurement.

[P]

will a solvent touch it? Leave it full of acetone for a few days and then rinse it out... if it was oily then the solvent might break it up a bit...  try pipe cleaners too?

[Furanone]

I have successfully ashed glass capillary viscometers in muffle furnaces at 550 oC before. It turns all the organic residue into a white fluff inside which can then very easily be washed out with water. I use only as last resort if other cleaning solutions just will not work, and inside residue is affecting results (ie changing pure solvent viscosity flow times).

Two key things to note: 1) it may remove or fade the paint that is on exterior of viscometer used as the measurement markings, so take detailed photos of all markings so the markings can be re-applied again after ashing if needed, and 2) since very fragile long slender glass pieces, you want to put glass viscometer in muffle furnace alone (nothing touching it), starting at 25 C heating up to 550 C and when finished (6-8 hours) turn off furnace leaving viscometer inside as to allow slow, gradual cooling back to room temp, since sudden changes in temperature (ie removing at 550 C into a 25 C room temp) could cause the long, slender glass lengths to crack.

[Saarith]

I was finally able to try cleaning it.

The sulfuric acid worked like a charm. After just one round where I let the sulphuric acid lie in the viscometer for 10 minutes and this is the result.

http://imgur.com/VQpBIrV

I should add that I had already tried to clean it with toluene to get rid of most of the oily residue.

Thanks again.