I'm currently etching brass using Ferric Chloride solution purchased
from Radio Shack. Obviously after a while the reaction slows down and
I have to replenish the etchant.
Currently I am disposing the spent ferric chloride by first
neutralizing the acidity with baking soda and then flushing down the
(Can anyone confirm if this is a good/bad/ugly disposal method?)
I have read many web pages that describe ways to regenerate the Ferric
Chloride using an oxidant - Hydrogen Peroxide has been mentioned more
than once. (Someone also suggested bubbling air through the solution
to slowly regenerate it)
Can anyone describe (quantatively) an "at home" way of regenerating
Ferric Chloride? I don't quite understand what happens to the
dissolved Copper salts - surely if they get converted back to Copper,
then the etching reaction will kick in again...?
I have about a 50% chemistry knowledge, so talk of anions, cations, et
al is OK, anything more and you might lose me...
You have converted copper(0) [the metal] into copper(II) ions (also called
cupric), by converting iron(III) ions (also called ferric) into iron(II)
ions (also called ferrous) - OK so far..?
By adding peroxide you will oxidize the iron(II) back to iron(III), and the
peroxide will turn into water.
Limiting problems. The peroxide you get is a solution, and therefore you
are adding water, this dilutes your concentration down, so you can't keep
regenerating (and anyway the copper salts will biuld up) - the other thing
to note is that by adding perioxide, you are not adding any counter ions
[the iron had 3 Cl, it drops to 2 Cl, and gives one to the copper - when you
add peroxide the iron would like 3 Cl again!] - you may need to add some
hydrochloric acid to redress the balance - or you will start getiing
precipitates of various hydroxides.
Don't repeat history, see unreported near misses in chemical lab/plant
at [Only registered users see links. ]
FeCl3 acts as oxidant and goes to FeCl2. Copper gets oxidised into a
soluble form (CuCl2). It stays in the solution, so even after
"recycling" = re-oxidising iron in the spent etching bath back from
Fe(II) to Fe(III), the copper will remain dissolved.
As recycling the stuff means you have changing concentration of
components, the properties (and performance) of the etching bath can
change and that could give you poorly consistent results.
My suggestion is to not recycle.
If you want to save money, buy FeCl3.hydrate (or hexahydrate) or FeCl3
solution in a chemical supply store in bulk and dissolve/dilute it
down to the right concentration. You do not have to be exact when
preparing your own solution, kitchen or letter scale would be
sufficient for the purpose.
Also, it is not the acidity but metal content which is unpleasant
about the spent bath. Neutralising it does not prevent fishes from
getting your copper, because the formed carbonate sludge will
eventualy dissolve. You are not nice disposing it in this way. But
copper is not as bad as many other heavy metals, in Arizona water is
naturaly high in copper and water stone formed in sink in AZ can even
have a bluish tint because of Cu. So if you don't get caught, you are
not being completely evil. (But never pour mercury, thalium, cadmium
or lead down the drain).
[Only registered users see links. ] (Steve H) wrote in message news:<email@example.com. com>...
The whole project is an exercise in negative economics, but could be fun.
I think that he could build a small chlorine generator and operate it with
The hazards are there, but if one is adept at the art, it is possible to do.
The salts should be removed as well as the Ferric Oxide.
This can be achieved through a distillation process.
My guess is that the NaHCO2 can be seperated through distillation and
what is left is recrystallized metal salts and the ferric oxide.
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