smaerd - 9-11-2012 at 17:15
well I have some smudges in some RBF's it was bound to happen after using them for a year or so. One is this burnt copper ligand compound something or
another and the rest are just goops and stuff from experiments gone wrong. I also would like to give my one second handed glass frit(chromatography
column) a nice cleaning. I've tried base baths, tried hot solvents, nothing really seems to get this one spot. I was told pirhana soln. is ideal for
frits and tough spots.
I was thinking of using maybe 10mL of some conc. H2SO4 and just adding a little bit of 3% hydrogen peroxide maybe an mL or two. Sure this isn't the
classic pirhana solution but I figure it would still do a damn fine job cleaning things up. Though I have a couple questions from a hobbyist
perspective.
1) could I neutralize the H2O2 with some sodium metabisulfite to dispose of it safely and without it eating trough my pipes or would it get exothermic
and boil all over my work area?
2) can I reuse the same 12mL's to clean with. Like clean a flask transfer the solution to another flask, pass it through the frit a few times, etc. Or
would it be best to use fresh stuff for each item.
Any advice would be very appreciated as I don't want to mess around with anything like this but some of my glass is over due for some serious
cleaning.
Nicodem - 10-11-2012 at 03:40
Just quench it by dilution into cold water or ice, and pour it down the sink. Don't quench it with reducing reagents - it is not needed and can be
dangerous.
I doubt a mixture of conc. sulfuric acid with 3% hydrogen peroxide could give an effective piraña solution. It could give a too diluted persulfuric
acid for your needs, while as you acknowledge, if you add too much peroxide, you will dilute it with water and this makes it totally ineffective. But
try out as you planed and maybe leave it to act on the frits more time.
Lambda-Eyde - 10-11-2012 at 06:39
Hmm... I wonder how peracetic acid would compare to piranha solution for cleaning. It is available in 25 L cans here for dairy farmers.
smaerd - 10-11-2012 at 09:11
Thanks for the advice. Truly appreciate that.
I went to this website - http://chem.chem.rochester.edu/~nvd/cleaningglassware.html
They mention using 3% H2O2 in a 1:1 volumetric ratio with sulfuric acid and claim it usually suffices for analytical purity. Could be a mistake but I
went with it anyways. What I did was mixed 50mL ice cold conc H2SO4 the drain cleaner variety with 30mL of 3% H2O2(to keep the balance more towards
sulfuric as you suggested). Added the H2O2 very slowly as the flask got too hot to hold pretty quickly. The yellow drain cleaner turned completely
clear and bubbled a bit, which I figured was a good sign.
I recycled this solution over and over essentially cleaning everything I own. I didn't realize how much crap was on everything. From translucent goos,
to metal ligand smudges to white rings at the bottom of flasks. This stuff is real. It ate up everything in a matter of minutes with
some swishing. Maybe theres some micrograms of contaminants but damn, impossible smudges are completely gone without a sign of them ever existing. I
was kind of surprised that the smells that came out from cleaning were a lot more of acetic acid and a lot less of sulfuric acid, must be oxidation of
those organics. Needless to say I had good ventilation going.
for disposal I used the ice water that I used too cool the H2SO4 down with and diluted the ~80mL to 1L added a fair bit of bicarbonate slowly just to
neutralize some of the stuff. After running it down the drain I followed it with maybe 20 liters of cold water(probably over-kill).
Went through about 5 nitrile gloves as every-time one got wet(from rinsing flasks after persulfuric acid treatment) I discarded it and washed my hands
with a little bicarbonate solution. Sure it's paranoid but hey my hands are fine and I survived my first encounter with this stuff unscathed.
Everything is squeaky clean. Mission accomplished.
I should invest in a tall glass tub and some stronger H2O2 for the next time I do this. Thanks again! Now to dirty them up again 
[Edited on 10-11-2012 by smaerd]
sargent1015 - 10-11-2012 at 12:38
Hmmm, might have to give this a try! Does it clean out glass frits real good?
smaerd - 10-11-2012 at 12:44
Haven't tried it on the frits yet but I will be doing some more tomorrow and hitting the last of my test tubes(got a little tired of cleaning glass).
My frits aren't too dirty just a little yellowing on the one. I have a feeling it would eat up just about anything though. I know some people use
nitric acid on frits. I have also heard running solvent the reverse way through a frit helps clean them out. I'll give it a shot and report back but
this is pretty painless way to really clean up glass so long as you're careful. Definitely recommend trying it especially because the solution is so
easy to make.
I am kind of curious as to how much more effective 30% H2O2 is because this has satisfied my needs.
[Edited on 10-11-2012 by smaerd]
Rob Lavington - 10-11-2012 at 13:29
Very interesting post, I am new to this forum and feel like a child in a sweet shop!!
I bought some kipps apparatus on ebay and it arrived with the most awfull deposits lodged inside.
I tried chromic acid without success.
On a whim I mixed up some aqua reiga and still nothing.
Then I tried heating the aqua reiga. As it started boiling the deposits slowly dissolved away, I could even see the acid creeping into the seized
quickfit joints freeing them as well.
I will try piranah solution next time.
jamit - 10-11-2012 at 15:25
Piranha solution is best for cleaning tough organic stain. You should use 30% hydrogen peroxide. I have cleaned many fritted funnels this way and
it's very effective.