# Staining



## Buzz (Mar 15, 2010)

Hi Guys,

I have a 2ltr vacuum flask that i was using to gravity filter a HCl/Bleach solution.

Normally, i empty the flask as soon as it's finished filtering but this time i got called away
and i let it sit overnight. I went out this morning and emptied the flask and there is a cloudy yellow/white 
staining in the bottom of the vacuum flask. 

Does anyone know how to clean this up?

I've tried water, cold and hot but it's not budging.

Also, i'm wanting to use the flask in a vacuum setup but cannot find a bung that will take a Buchner filter.
The flask neck opening is 45mm and the funnel tapers from 30mm to 25mm.
Anyone know where i might be able to get a few bungs to fit?
I really need to speed this filtering up a bit so any help would be appreciated.

Regards
Buzz


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## Irons (Mar 15, 2010)

Buzz said:


> Hi Guys,
> 
> I have a 2ltr vacuum flask that i was using to gravity filter a HCl/Bleach solution.
> 
> ...



A number 9-9.5 stopper will do the trick. If you can find a bit of neoprene foam like what is used in wet suits for diving, you can cut a circle about 60mm with a hole in the center with a tight fit for the buchner. That should seal it.

I take a household scrubbing sponge, the ones with sponge on one side and nylon scrubber on the other. Cut it up into 1/2 inch (13mm) bits and put it in the flask with a little dishwashing soap and just enough water to soak the sponge. Swirl around until stains are gone. rinse. Save the bits for the next flask.

My bathtub drain stopper fits a 2 liter filter flask. That might be easier to find.


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## Buzz (Mar 15, 2010)

I'll give that a try, sounds like a plan.

Thanks again for the bath tub stopper idea too!

Regards
Buzz


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## Oz (Mar 15, 2010)

For that kind of staining I find that a few tablespoons of table salt (a little baking soda helps) and a couple of ice cubes will often do the trick. Just swirl it around until the ice is melted. The salt is a non-scratching abrasive and the ice just helps push it around in those hard to reach areas.


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## goldsilverpro (Mar 15, 2010)

A little aqua regia works well on many things.

http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/al_techbull_al228.Par.0001.File.tmp/al_techbull_al228.pdf


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## Irons (Mar 15, 2010)

goldsilverpro said:


> A little aqua regia works well on many things.
> 
> http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/al_techbull_al228.Par.0001.File.tmp/al_techbull_al228.pdf



I didn't think anyone used Chromic Acid any more. That's some nasty stuff. I remember getting ulcers on my hands from even a tiny scratch in contact with dilute CA. They took months to heal.


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## goldsilverpro (Mar 15, 2010)

> I didn't think anyone used Chromic Acid any more. That's some nasty stuff. I remember getting ulcers on my hands from even a tiny scratch in contact with dilute CA. They took months to heal.


When I was in plating, in the 60s, I worked in a place that had several chrome plating tanks. The largest was probably 2000 gallons and was used for car bumpers. The chromic acid concentration in most of the tanks ran about 2#/gallon. Chrome baths are very inefficient at the cathode and inert (lead) anodes are used, so there's a lot of gassing at both electrodes which creates a chromic acid mist around the tank. I remember chromic acid stalactites, about a foot long, hanging from the ceiling above the tank.


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## 4metals (Mar 15, 2010)

When I was back in college we used a product called Chromerge, it was chromic acid which you added to a 5 pint bottle of sulfuric acid. It worked extremely well at cleaning glassware, and at polluting the groundwater, killing fish and wildlife, and who knows what else. 

Today they sell a powder called No chrome mix, which is added to the same 5 pint bottle of sulfuric acid and it also works well. With no chromium in the equation! 

Recently I had a guy who couldn't reproduce any assays. From checking out his place it became obvious that his problem was dirty glassware. I had him clean the glassware once with the no chrome mix and then do follow up cleanings with Alconox. Problem solved. Good housekeeping and analytical chemistry go hand in hand.


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## Lou (Mar 15, 2010)

Acetone and rock salt is a favorite of mine. Also effective is dilute ammonia, especially if this is silver related.

Aqua regia works great for frits (which should never be base-bathed) and for metal-ridden surfaces.


For the most part, soap and hot water is what I first turn to and then I progress as needed.


Chromic acid is nasty and has largely been replaced. Doesn't mean I haven't seen some in recent months...


The NoChrome stuff is ammonium peroxydisulfate and forms a weak version of Caro's acid.


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