I've seen what you have just described. What you are doing when
adding water to a dark solution of CuCl2 and some CuCl is the
CuCl precipitates out as what solid on dilution, thus leaving
only green CuCl2. The CuCl is only soluble (which makes the
solution dark brown) when the chloride ion concentration is high.
Diluting will of course also reduce the concentration of CuCl2
and slow down etching rate.
If you bubble enough air through the solution it ∗WILL∗
eventually go deep green. Put a drop on a white piece of plastic
and come back in a few hours, if turns clear green then it means
the solution is not complete regenerated. Fine bubbles are many
times more efficient at regeneration than large bubbles. Aquarium
airstones are ideal. It can take an hour or more of vigorous
bubbling.
Adam.
frajopea wrote:
> Hello,
>
> I've been reading for a few weeks now, this is my first post.
>
> There was a post about regenerating FeCl using HCl, I had a bunch of
> used up and very rusty etchant lying around so I did it. I poured HCl
> in the used etchant and the result was a very nice clear green/bluish
> solution that etched boards again. I was impressed.
>
> Then there was the CuCl2 thread, where you just use copper, HCl and
> H2O...
>
> With all this in mind, I kept using my regenerated etchant and
> pouring some HCl every now and then when it started to look brown.
> The thing is, now the etchant is brown, no matter how much HCl I put
> in it, I can't get it back to the clear transparent green I first had.
>
> The other day, I was cleaning a board using water and: the clear
> green solution!... I made the experiment of adding water to a sample
> of the etchant and it did change color and turned clear green. The
> only problem is: it didn't etch, at least not fast enough for me to
> notice.
>
> Now, I don't know enough about chemistry to figure this out, but is
> it possible that if I add copper and do the bubbling, that it'll turn
> clear green again? I mean, I think there's too much HCl and not
> enough of the other stuff!
>
> Thanks,
> Fp
> www.tonepad.com
>
>
>
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