Conc. Alkali + KMnO4 as a Cleaning Mixture for Glasswares
Mohammed Farooq
making a very concentrated solution of sodium hydroxide and potassium
permanganate for cleaning glasswares. The mixture still remains purple
and seems to work perfectly with perhaps one drawback, the dirty
glassware becomes brown due to a film of maganses dioxide, therefore
after treatment it is washed with dilute nitric acid containing
hydrogen peroxide, which immediatley removes the brown color and thus
glass becomes perfectly clean. The efficiency seems to be equivalent
to conc. H2SO4-dichromate mixture. The solution of cocn. NaoH + KMnO4
also turns green (due to formation of manganate) on contact with
glassware and later brown, if it is very dirty. It is excellent for
removing white films of detergents or grease which are is removed
even by dilute nitric or sulfuric acids. I do not have a reference to
this method, Is this method acceptable?
The only apprehension is that does washing volumetric flasks, pipettes
or burettes with concentrated alkali solution ( a contact of less than
10 minutes) can damage the glass, BTW there is no visble damage?
Muhammar
be washed with conc. HCl afterwards, etc.
I like using a diluted common liquid laundry or floor-washing
detergent with added K3PO4 + KOH. It works beautiful, for a soak bath,
overnight.
faro...@hotmail.com (Mohammed Farooq) wrote in message news:<66756669.04072...@posting.google.com>...
Steve Turner
wrote:
Have you ever tried a simple base bath? The "recipe" is a pound or
two of NaOH in a gallon or two of about 50% ethanol. (There is a LOT
of leeway in proportions.) I have rarely had this type of bath fail,
though it sometimes takes a few days (particularly when it starts to
get old). It would not be acceptable for use on volumetric glassware,
however.
Steve Turner
fkasner
From neither of these methods do you really get clean glass. What you
get is glass with a surprising amount of adsorbed materials on the
surface. Such stuff would never do for preparing very dilute solutions
and certainly would be a disaster for conductivity experiments. You
would have to bathe these containers repeatedly in very good distilled
water for protracted periods before you had removed the adsorbed ions on
the glass. I did some work that dealt with very dilute solutions. But I
used quartz containers and they had never been used before. And I kept
very carefully distilled water in them at all times. And only put dilute
solutions in them after carefull emptying and draining. Conductance
measruements indicated that the process worked well as did concentrating
some of the solutions and then do a volumetric analysis. Soaking
glassware in strong oxidizing or glass attacking chemicals is asking for
trouble.
FK
Steve Turner
wrote:
> From neither of these methods do you really get clean glass. What you
>get is glass with a surprising amount of adsorbed materials on the
>surface. Such stuff would never do for preparing very dilute solutions
>and certainly would be a disaster for conductivity experiments. You
>would have to bathe these containers repeatedly in very good distilled
>water for protracted periods before you had removed the adsorbed ions on
>the glass. I did some work that dealt with very dilute solutions. But I
>used quartz containers and they had never been used before. And I kept
>very carefully distilled water in them at all times. And only put dilute
>solutions in them after carefull emptying and draining. Conductance
>measruements indicated that the process worked well as did concentrating
>some of the solutions and then do a volumetric analysis. Soaking
>glassware in strong oxidizing or glass attacking chemicals is asking for
>trouble.
>FK
Yes, the preferred method for cleaning glassware will depend, among
other things, on its intended use. Base-bathing is SOP in many
organic labs, where large amounts of tarry insoluble organic materials
may be stubbornly adhered to glassware, and where trace ionic
components are normally of no concern.
Steve Turner
Mohammed Farooq
Then what is best cleaning mixture that is relatively safer (ie should
not be carcinogen) as well as the one that does not attack volumetric
glasswares? I use dishwashing detergents ( or sometimes washing soda
as a mild abrasive) for glasswares, but it is sometimes frustrating
that drops adhere inside a pipette or burette even after thoroughly
washing with a detergent ie the ideal condition of un-broken film of
water can not be achieved.
hanson
> faro...@hotmail.com (Mohammed Farooq) wrote in message
news:<66756669.04072...@posting.google.com>...
> > Since dichromate has been proved to be a carcinogen, I thought of
> > making a very concentrated solution of sodium hydroxide and potassium
> > permanganate for cleaning glasswares. The mixture still remains purple
> > and seems to work perfectly with perhaps one drawback, the dirty
> > glassware becomes brown due to a film of maganses dioxide, therefore
> > after treatment it is washed with dilute nitric acid containing
> > hydrogen peroxide, which immediatley removes the brown color and thus
> > glass becomes perfectly clean. The efficiency seems to be equivalent
> > to conc. H2SO4-dichromate mixture. The solution of cocn. NaoH + KMnO4
> > also turns green (due to formation of manganate) on contact with
> > glassware and later brown, if it is very dirty. It is excellent for
> > removing white films of detergents or grease which are is removed
> > even by dilute nitric or sulfuric acids. I do not have a reference to
> > this method, Is this method acceptable?
> > The only apprehension is that does washing volumetric flasks, pipettes
> > or burettes with concentrated alkali solution ( a contact of less than
> > 10 minutes) can damage the glass, BTW there is no visble damage?
>
news:a6cffac9.04072...@posting.google.com...
> This oxidation mix of yours is ugly. MnO2 deposits everywhere, has to
> be washed with conc. HCl afterwards, etc.
> I like using a diluted common liquid laundry or floor-washing
> detergent with added K3PO4 + KOH. It works beautiful, for a soak bath,
> overnight.
>
Not only for glassware but this (1) NaOH/KMnO4 70/30 mixture was/is
used in enormous industrial quantities at 1 lb/gal & 180°F as "conditioner"
to overhaul/clean ferrous and Titanium parts of jet engines (like GE JT8D)
in swimming pool size tanks. The immersion took some 10-15 min and
was followed by a water rinse.
Then another immersion into a bath containing (2) NaOH/Na-Gluconate
70/30 at 1 lb/gal & 180°F for 15 min followed and a 2-3 rinses.
(1) oxidized soot, other organics and metal dust deposits.
(2) chelated the MeOx's, solubilised them along with residual R-COOH's
formed in (1) and dissolved away any MnO2.
Parts looked like brand new with NO metal loss after this chemical cleaning
porcess that involved no mechanical scrubbing efforts.
All susceptible high strength steels were baked at 375°F for 3 hrs to
relieve any Hydrogen-embrittlement.
hanson
Bob Rodgers
alkaline permanganate followed by 6N HCl to get things clean.
Prolonged soaking in the base is NOT recommended for volumetric
glassware, but we did use it to clean calibrated pipets.
The HCl generated CL on the surface where the MnO2 had been deposited.
What the Mn04 didn't kill, the Cl did!
Steve Turner
wrote:
>Then what is best cleaning mixture that is relatively safer (ie should
>not be carcinogen) as well as the one that does not attack volumetric
>glasswares? I use dishwashing detergents ( or sometimes washing soda
>as a mild abrasive) for glasswares, but it is sometimes frustrating
>that drops adhere inside a pipette or burette even after thoroughly
>washing with a detergent ie the ideal condition of un-broken film of
>water can not be achieved.
When I was in school (back around the time of Moses), I was taught
that volumetric flasks used for aqueous solutions should never be
dried on the inside. Today I keep a few of these around for
occasional use in preparing solutions. They are always kept wet on
the inside, and I've never had a problem with water flowing in a film.
Of course, they never get very dirty either.
In your case, a key factor will be what it is that is making the
glassware dirty in the first place. This will determine the "best"
method for cleaning (if there IS a "best" method). Use chemistry
whenever possible -- HCl to remove insoluble carbonates is but one
trivial example.
Steve Turner
Mohammed Farooq
By chance, I found the very same method mentioned in a monograph on
"Volumetric Analysis" by G. Fowles-1957 pg 35 as:
"Another method is to fill the burette with a strong neutral solution
of potasium permanganate for some DAYS previous to use, run out the
permangante and add warm dilute hydrochloric acid to remove any
manganese dioxide preciptated on the glass."
Perhaps this method is no longer used.