Sciencemadness Discussion Board

Cleaning Inside of Flask

mrjeffy321 - 23-12-2006 at 23:07

I have a flat-bottom flask which got a little dirty today in the course of an experiment.
On the inside, round part, of the flask there is some residue which does not wash out. It should not be too difficult to remove the residue if I only could reach in there and wipe it off, but there within lies the problem…I cannot reach in due to the narrow throat of the flask.

Instead of me haphazardly trying to reach into the flask with a bent wire and a cloth, is there a better technique to use? Or will mounting a cleaning pad at the end of a clothes hanger wire work out?

kaviaari - 23-12-2006 at 23:50

Have you tried consentrated sulfuric acid mixed with potassium dichromate. It quite literally eats up everything exept the glass. Other way round would be a ethanol-sodium hydroxide mixture. Usually, when using violance, you just end up with broken glassware.

Do you have any idea what the residue is?

leu - 24-12-2006 at 00:35

Some information about cleaning glassware from the Chemical Formulary:


Cleaning Laboratory Glassware
Formula No. 1
For bottles, use a test bottle washer or place the bottles in a suitable rack with perforated or slotted cover and immerse. A cleaning solution made of 1 oz. of a good grade of washing powder to a gallon of water and heated to 130°-150° F. will be found satisfactory. Scrub the inside only with a brush having soft bristles. Rinse in hot water to remove all traces of the cleanser and invert the bottles to drain. Do not soak the bottles too long.
When very dirty, greasy bottles must be cleaned, a very good cleaning solution can be made by dissolving 31/3 oz. of potassium dichromatic in 1 qt. of water, and slowly adding to this 1 qt. of sulphuric acid. This solution will remove all traces of grease after sufficient soaking, but care must be taken to keep it from prolonged con­tact with the outside of the necks, be­cause of its effect on the enamel in the lines and numbers.
No. 2
Take a 10 oz. cake of a good grade of cleaning and polishing grit cake soap, such as "Bon Ami" and pul­verize it to a powder with a mortar and pestle. Cut a 12 oz. cake of a good grade of rosin laundry soap, such as "Octagon," into thin slices and add just enough water to cover the mass. Slowly heat on a hot plate until the soap has dissolved in the water and a clear solution results. Add this liquid soap mixture to the powdered grit cake in a beaker or earthen jar, stirring the mixture well. Allow to stand overnight or until the resulting mixture has solidified into a soft mass. The mixture can then be easily applied to the wet glassware in the usual manner with a brush or the hands, scrubbed thoroughly and finally rinsed in running water. It is only necessary from time to time to add small quantities of water to keep the mixture at the proper consistency. To make a larger supply increase the quantities accordingly.

Removal of Tars and Carbon Residues from Glass Equipment
Distillation flasks and other equip­ment which have contained tars, or flasks which have been used for dis­tillations in which tars and carbon residues are formed, can usually be cleaned when all other methods fail by treatment with a hot concentrated solution of sodium hydroxide to which small amounts of potassium per­manganate have been added. The strong oxidizing powers of perman­ganate solutions are especially effec­tive on tarry materials. At times it may be necessary to repeat the treat­ment, and to boil the solutions for a time. This method has been found to be much superior to those using boil­ing acids and solvents, and much better than alkaline solutions by themselves. The economy of materials employed makes it available to all.
.
Cleaning Organic Smears-Tars, Etc.-from Apparatus
Put the dirty beakers, test tubes, distilling flasks, etc., into a large evaporating dish containing concen­trated commercial sulphuric acid heated to 200-225° C. (400-435° F.). Small quantities of nitric acid should be added whenever the heated acid becomes black in color. Large beakers can be turned around sufficiently to bring all parts into the hot acid. When the apparatus is clean, remove (use a glass rod) and allow the articles to cool before rinsing in water. This cleaning solu­tion is not satisfactory for petro­leum products. This solution is much more economical than chromic acid solutions-the same acid can be used many times.
Caution: Have beakers, flasks, tubes, etc., pointed away from the operator while they are being put into, the acid. Sometimes the reac­tion with wet, very dirty apparatus causes a spattering of acid from the open end of the vessel. The acid should be kept in a glass-stoppered bottle when stored.
Cleaning Flasks or Other Apparatus from Baked-In Carbon Deposits
Put a small quantity of potassium chlorate in the dry flask; heat the flask gently in a Bunsen burner flame until the chlorate is barely melted; rotate the flask so that the molten chlorate comes in contact with the carbon. The quantity of chlorate to contact the carbon resi­due is surprisingly small. After cool­ing. dissolve the remaining mixture in water. Caution: Use this only on the solid carbon stain that will not wash out or that cannot be removed by ordinary mechanical means.
Chromic Acid Cleaning Mixture
This is needed for apparatus such as burettes, etc., which cannot be immersed conveniently in a vessel of hot sulphuric acid.
Add 1 1. of cone. commercial sul­phuric acid to 50 g. chromic acid dissolved in 25 cc. of warm water. There will be no trouble from crys­tallization of salts from this mix­ture. This mixture, without heating, removes organic material after a few hours of contact. More chromic acid can be added whenever the so­lution loses its red color. Caution: Keep in a glass-stop­pered bottle. The reason: absorp­tion of water from the air reduces the activities.
Cleaning Laboratory Glassware
lodoform stains and odor may be removed by washing glassware with a solution of potassium or sodium hydroxide and rinsing it with a small amount of alcohol. Of course, the final step in this cleaning opera­tion. as well as in all others to be described, is thorough washing with soap and water. Ferrocvanide or iron stains are easily and rapidly removed with a solution of potassium hydroxide. Lime deposited by lime water or similar preparations can be removed from glassware with diluted solutions of acetic acid or nitric acid. Deposits from lead subacetate solution can also be removed with these cleansing agents.
Deposits of soluble metallic salts are usually readily removed by thorough rinsing with water; how­ever, in some cases, a small amount of hydrochloric acid may facilitate the cleansing. Insoluble or practi­cally insoluble salts may be re­moved from glassware by dissolving them with the appropriate solvent which differs for each salt. Metallic soaps, such as oleates and lead plaster, may be removed by oil of turpentine.Oils, resins, balsams, and similar resinous bodies can usually be re­moved with soap, but in some cases a solution of potassium hydroxide may be required.
Collodion may be removed by peeling it off the glassware. If, how­ever, the film adheres firmly, a mix­ture of ether and alcohol will remove it. In the case of adherent gutta­percha film, chloroform should be used as the solvent.
Sawdust is one of the best mate­rials for removing petrolatum, lard, or other greasy substances from mortars and ointment tiles. Paper cleansing tissues are also excellent for this purpose. After the greater part of the grease has been removed with the sawdust or paper, the glass­ware should be washed with soap and water.

:D

nightflight - 24-12-2006 at 02:40

Just use some towel (paper or wool) and put it into the flask, jusdt enought thatit fills the flask out and ca thus be moved with a stick around the wall; use a stick and move the ball around to clean it, then pull it out.

does the trick for me.

mrjeffy321 - 24-12-2006 at 14:08

I cannot believe I didn’t try this before, but I was able to clean out the flask using some Hydrochloric acid.
The residue inside the flask was some MnO2.
So by adding the HCl, I was able to turn the small amount of MnO2 on the sides of the container into the highly soluble MnCl2 which washed right out and now the glass is crystal clear again.

Would the Potassium Dichromate / Sulfuric acid cleaning solution be used more for organic residue?

12AX7 - 24-12-2006 at 17:11

Ah, sodium metabisulfite works wonders on MnO2 stains.

Tim

UnintentionalChaos - 24-12-2006 at 17:50

This needs to be more common knowledge....I have plenty of stuff with MnO2 stains and something like a pound of metabisulfite lying around. They will be quite clean now. Thanks!

DeAdFX - 24-12-2006 at 18:07

I use oxalic acid for removing metal oxides. The oxalic takes awhile to dissolve the oxide but it works great.

mrjeffy321 - 24-12-2006 at 22:07

The Hydrochloric acid worked pretty well, but I will try the Sodium metabisulfite next time. Is there a common source for Sodium metabisulfite? I think it is used in home, beer, brewing so I will check a local store that caters to this application to try and get some.

UnintentionalChaos - 24-12-2006 at 22:45

I'm not sure about beer, but I know metabisulphite is used in wine making because the sulfur dioxide it releases when dissolved in water inibits wild bacteria and yeasts from growing in the wine. I imagine that it would serve a similar purpose if making beer. You can also get citric acid crystals (If you have some need for them) dirt cheap.

12AX7 - 25-12-2006 at 00:56

Stump killer that isn't KNO3 (like Bonide's) is where I have mine from.

Huh, citric acid would probably work pretty well, too. Acidic and reducing enough to grab up Mn(IV), and probably forms a complex (presumably, soluble. .) with Mn(II) or Mn(III) to boot.

Tim

Darkblade48 - 25-12-2006 at 01:15

Like DeAdFX, I use oxalic acid for my MnO2 stains, and it works so much faster than scrubbing glassware.

Ozone - 25-12-2006 at 08:17

Merry Christmas Everyone!

Like bisulfites, a solution of hydroxylamine will also quickly remove MnO2; it is added to the digestion mixture post-oxidation (KMNO4/K2S2O8) when carrying out the EPA analysis for Hg (Hg via cold vapor). It will also reduce Fe3+ to Fe2+ when carrying out the colorimetric test for Fe using o-phenanthroline.

For more about sulfititation of wine, look up "mutage".

Oxalic acid (and likely succinic, tartaric, malic, etc. and EDTA(or EGTA)/acid) all work nicely via first solution (acid part) then chelation. CLR(TM) cleaner contains, I think, gluconic acid and it works well with rust, etc.

Otherwise, 1:1 HCl in a squirt-bottle is a handy cleaning tool; if this fails HNO3 (conc.) will chew off most residues (DO NOT use a bottle brush with this--it will eat the bristles off!).

Best wishes,

O3

Sauron - 25-12-2006 at 09:47

Chromic acid (sulfuric acid and a dichromate) used to be routine for cleaning glassware; another mainstay was saturated ethanolic KOH. Both are now in disfavor, the former because of enviromental concerns about the hexavalent chromium (carcinogen.) The latter often contaminated ground glass joints and fritted ware and is well nigh impossible to completely remove or neutralize. The result can be deleterious effects on sensitive compounds subsequently in the affected glassware.

Corning's Pyrex catalog gives good advise on glassware cleaning

So do many other glassware catalogs (Ace, ChemGlass, Kimble/Kontest etc.)

Beware of buying second hand glassware (eBay, LabX), most of the time you will get bargains but sometimes you will get a problem piece of glass that was etched by a F-compound, or strong alkili, or hot phosphoric acid -- all of which can attack borosilicate glass. In that event the best thing to do is to pitch it out.

pantone159 - 25-12-2006 at 11:21

Quote:
Originally posted by mrjeffy321
Is there a common source for Sodium metabisulfite? I think it is used in home, beer, brewing so I will check a local store that caters to this application to try and get some.


My local homebrewing supplier (both beer and wine, I think) has metabisulphite.

cleaning glass continued with a question

chemrox - 2-11-2007 at 12:23

I washed my adapter with H2SO4/Cr2O7 and it came out looking dirtier than ever. Without stopping to consider, I mixed 37% HCl with 30% H2O2. First it turned a little greenish-yellowish, like the appearance a highlighter might make on glass. After 30 sec to 1 min it started bubbling like crazy. I did what I could to secure my adapter and placed it and the flask as close to the exhaust as I could. It seems I'm making hypochlorous acid and releasing HCl and Cl2 (?)

12AX7 - 2-11-2007 at 13:04

2HCl + H2O2 = 2H2O + Cl2(g).

You might get H2O2 + Cl- <==> OCl- + H2O, but not in acid conditions (even mild (pH < 5), let alone strong acid), where OCl- is actually HOCl which decomposes easily to Cl2.

Edit: As long as I'm giving numbers, I might cover my ass to more particular minds by stating that HOCl has pKa = 7.53. In my experience, it starts decomposing appreciably (to Cl2) below pH = 6 (the pKa of dichromic acid, being 6.5).

Tim

[Edited on 11-2-2007 by 12AX7]

Eclectic - 2-11-2007 at 13:29

You are getting some chlorine, but it's probably mostly O2 from catalysed H2O2 decomposition. AFAIK, the only halogen acid H2O2 will completely oxidize to free halogen is HI. With the others, I think it's a back and forth oxidation/reduction unless there is a halogen acceptor, or something else in the mix that can be oxidized, like SnCl2 to SnCl4, or Cu(metal) to CuCl2.

cleaning my glasss

chemrox - 31-1-2009 at 16:53

The frustration continues .. after work I often let some things sit a day or two. Just as often I drop the glass into the sink with alconox solution in it. A majority of my glass has persistant areas that bead up when rinsed... I can hardly afford to clean with pirhana after every experiment. I think the chromic was attacking the stopcock grease and spreading teflon impregnated grease all over some of the pieces. Anyway, from somewhere I'm getting this stuff that will not clean up. I washed glassware for a year in school so this is really bending my brains. I'm doing things with amines and esters.. haven't quite got to the r.e. metals yet but these cmpds. are to become organo-metallic compounds by and by. Not with dirty glass though....
ARGGGH!!!

crazyboy - 31-1-2009 at 17:29

I usually use kosher salt and a small amount of cold water the abrasive salt usually gets most stuck on stuff otherwise I use sulfuric or hydrochloric acid.

S.C. Wack - 31-1-2009 at 19:01

Perhaps more relevant to the OP are curved brushes. I have an assortment and forget where I got them. They were specifically sold for certain sizes of flasks. I think they were from Cynmar, and they look the same as what they sell now. They have fewer, softer, and thinner bristles than something you'd see in a kitchen.

I can't believe that everyone doesn't know to use HCl for manganese. I like chromic acid in general, and nitric acid is good too. Nothing beats good old environmentally unfriendly phosphate for squeaky clean glass.

Coyne, for one, has plenty of hints on glass cleaning.

chemrox - 1-2-2009 at 00:31

I think I'm not mixing my soap concentrated enough. @ SC Wack- I just got some new curved brushes and hinged ones too. You were touting TSP? I will add some to the more concentrated alconox and keep a pot full of technical sulfuric with a little nitric added from time to time as color develops. There's a really good article much earlier in this thread about cleaning glass that I'm trying to internalize. Thanks to @leu

Klute - 1-2-2009 at 10:45

Use a base bath! I keep on telling everyone that this is really a good solution for cleaning glassware, I use it routienely and am nearly always satisfied with a single night's soak..

The bath can be kept for months, depending on how much you use it, and only very rarely does a stain resist. In that case a pirahna will usually do the trick.

In the event of require drasticlyy base-free glassware, an acid soak (10% HCl) overnight will clean glass frits etc, but I really never found the need for this, even when working with organometallics.

Panache - 2-2-2009 at 05:29

Quote:
Originally posted by S.C. Wack
Perhaps more relevant to the OP are curved brushes. I have an assortment and forget where I got them. They were specifically sold for certain sizes of flasks. I think they were from Cynmar, and they look the same as what they sell now. They have fewer, softer, and thinner bristles than something you'd see in a kitchen.


Make your own using wire, scouring pads and a cordless drill. Since i discovered how easily you can make a brush of any size, shape or specific function i rarely bother with soaking anymore unless the glassware is very awkward.

Basically cut a length of wire, fold in half and place in the chuck of the drill, roughly hold the scouring bristiles in places whilst holding the end of the wire, hit the trigger, voila!! Vary the thickness of the wire, the density of the bristle etc etc to fine tune your brush. I have about 15 brushes now and use most of them.
If you're really clever you can whittle a maple handle for it, but i'm lazy.

zed - 2-5-2009 at 22:59

Well, the soda jerks down at the local greasy spoon used to clean out their oily glass coffee pots, by putting some dutch cleanser in them, filling them with ice cubes, and then swirling and shaking them until they were sparkling clean.

Worked pretty well. Sand and ice cubes, might also work. Kind of abrasive, and I suppose eventually, using this technique might etch the insides of your glassware.

[Edited on 3-5-2009 by zed]

Magpie - 3-5-2009 at 10:39

A related problem is cleaning a mortar. I tried mild abrasives but they didn't work too well. But by adding a little sodium bicarbonate dampened with water, then grinding away with the pestle, most contaminants can be removed pretty well.

Peroxymonosulfuric acid

pHzero - 17-5-2009 at 09:33

Sulfuric acid+Hydrogen peroxide ---> Peroxymonosulfuric acid, aka pirhana solution. It dissolves pretty much everything, so it should do the trick. The perxoxy group makes it particularly effective against organic compounds

And I can understand why metabisulfates so effective against MnO2 - it reacts with water to form SO2, which reacts with insoluble MnO2 to make soluble MnSO4. If you dont have any metabisulfate, i expect if you held the flask over burning sulfur, that'd do the trick too

UnintentionalChaos - 17-5-2009 at 12:29

I have a very nice heavy ceramic mortar and pestle that ocasionally gets used for powdering oxides and other things that really don't want to come out. I've tried everything. Base, acid, reducing agents, etc. When I finally give up, I throw a decent amount of moderately coarse white sand in there and grind until it's a fine powder. A rinse and it looks good as new again. I know I'm removing ceramic, but the walls are so thick, it'll be many years before that becomes an issue.

setback - 18-5-2009 at 19:50
Quote:

Like bisulfites, a solution of hydroxylamine will also quickly remove MnO2; it is added to the digestion mixture post-oxidation (KMNO4/K2S2O8) when carrying out the EPA analysis for Hg (Hg via cold vapor).


Hey! I used to do that. In the sample cup goes DI, a minute amount of HNO3, H2SO4, then the KMNO4 and persulfate. Heat it up, cool it down, then add the hydroxylamine.

Yes, I actually used to use the hydroxylamine to clean up KMNO4 stains, works like a charm.

tahallium - 16-3-2020 at 16:47

Can I remove traces of Mercury, lead, thallium?