Re: [Histonet] Glass cleaning for silver
If there are traces of mmetallic silver on the
glass, they act as catalytic centres in the
reduction (development) stage of the silver
method and more silver is deposited on them,
instead of in the correct places in the
sections. If you do gold toning, the silver
deposits are largely changed to gold, which
cannot be removed with nitric acid.
Deposition of silver on glass is a problem
especially with techniques in which concentrated
silver nitrate is deliberately carried over
into the developer. The Gros-Schultz method
for axons is an example. There can also be
deposition if solutions are left in Coplin
jars or staining tanks after use.
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London, Canada N6A 5C1
Gudrun Lang wrote:
> What happens with the silver stain, when class with traces of metallic
> silver is used?
> We don't do this cleaning in our lab, and had no problems until now.
> Gundi Lang
> ----- Original Message -----
> From: "John Kiernan"
> To: "Behan, Rosemarie G"
> Sent: Wednesday, September 17, 2003 7:28 AM
> Subject: [Histonet] Glass cleaning for silver
> > Rosemary Behan
> > asked about cleaning glassware
> > for silver staining.
> > A reply follows.
> > It's necessary to remove traces of metallic silver,
> > which are not necessarily visible. The only common
> > acid that does this is nitric. Here is what I do,
> > with rationale. Let's assume the vessel is a Coplin
> > jar.
> > Rinse with one or two changes of distilled water.
> > [Tap water contains chloride ions and silver
> > chloride precipitation must be avoided.]
> > Pour a few ml of concentrated nitric acid into
> > the vessel and carefully let it wet all the
> > inside surface. For a Coplin jar it's important
> > to dissolve silver from all corners and from the
> > slots for supporting slides. It takes 15-30
> > seconds to make black deposits or mirrors
> > disappear. A minute of turning and tilting has
> > to be enough to remove all the visible and
> > invisible silver.
> > Safely discard the nitric acid and fill up the
> > vessel with distilled or otherwise purified
> > water, three times.
> > [Pure water must be used because tap water
> > will precipitate traces of silver chloride
> > from the residual nitric acid - which contains
> > dissolved silver nitrate.]
> > Wash in tap water, detergent etc as for any
> > other dirty lab glassware, and don't spare the
> > brush.
> > [The nitric acid treatment does not remove
> > all types of dirt. Bits of detached section,
> > stuck to the glass, are made yellow by nitric
> > acid.]
> > Rinse in tap water, repeatedly, to get
> > rid of the detergent (no more froth with
> > shaking) and then in 3 generous changes of
> > pure water to dilute out residual chloride
> > from the tap water.
> > Let the vessel dry by drainage and evaporation,
> > then keep it in a closed cupboard, with its
> > lid on (if it has a lid; and don't forget to
> > clean the lid).
> > If glassware is contaminated by insoluble silver
> > compounds such as silver chloride, 5% sodium
> > thiosulphate (10 minutes) will remove the silver.
> > [The thiosulphate ion strongly complexes silver
> > ions and will remove them from solid silver
> > halides. This is the "fixation" of photographers.]
> > In the above remarks I have not given detailed
> > safety and disposal instructions. Conc. nitric acid
> > is nasty stuff but becomes harmless when diluted
> > with water.
> > Do not use hydrochloric acid or an HCl-alcohol
> > mixture for "acid washing" of glassware that will
> > contain silver nitrate or protargol.
> > [Reason is obvious from above discussion.]
> > There are silver solvents less noxious than
> > concentrated nitric acid. The best known one is
> > Farmer's reducer. This is used in black & white
> > photography for controlled removal of darkness
> > (= silver) from negatives or prints. It is a
> > solution containing potassium ferricyanide and
> > sodium thiosulphate. Its actions on photo media
> > take several minutes, but it takes much longer
> > to weaken silver deposits on glassware and in
> > overstained sections (my unpublished anecdotal
> > observations).
> > For what it's worth, I think concentrated
> > nitric acid is the best cleaner of glassware
> > used for silver methods. I also think that
> > poor glass-hygiene (dishwashers etc etc etc)
> > often causes failure or poor results with
> > many staining techniques.
> > --
> > -------------------------
> > John A. Kiernan
> > Department of Anatomy and Cell Biology
> > The University of Western Ontario
> > London, Canada N6A 5C1
> > email@example.com
> > http://publish.uwo.ca/~jkiernan/
> > --
> > (Rosemary Behan: I've deleted many irrelevant
> > messages from the tail of your email, which
> > contained a megabyte of unrelated stuff.
> > Please be careful about what to quote!)
> > _____________________________________
> > "Behan, Rosemarie G" wrote:
> > >
> > > I am looking for a recipe for acid cleaning glassware to do silver
> > > can anyone help me?
> > __________________________________________________
> > _______________________________________________
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> > Histonet@lists.utsouthwestern.edu
> > http://lists.utsouthwestern.edu/mailman/listinfo/histonet
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