That makes it all more clear, thanks!
I just used some of this regenerated etchant and it's working fine, only it takes a little longer for the board to etch, but it's nothing compared to not having to buy any more or throw this stuff away!
Thanks!
Fp
www.tonepad.com
----- Original Message -----
From: Adam Seychell
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, April 27, 2003 10:17 PM
Subject: Re: [Homebrew_PCBs] Home made etchant
CuCl is copper(I) chloride, it is almost insoluble in water. When
chloride ion concentrations is sufficient (e.g. from HCl or
CuCl2 or NaCl ect.) the solubility increases because copper(I)
complexes with chloride ions. This complexed form of copper(I)
chloride is dark brown. It doesn't take much concentration of
copper(I) chloride complex to make it appear opaque.
CuCl2 is copper(II) chloride and is very soluble in water. At low
concentration the color is pale blue, at higher concentration it
goes clear green, and gets darker green as concentration
increases. At typical concentrations used for etching the
copper(II) chloride is a very dark green , that you cannot see
through more than 1 inch when looking through a bright light. If
the splashes on the side of the container look clear green then
its pretty much all copper(II) chloride and very little copper(I)
chloride. You can be sure that regeneration is completed.
Francisco Peña wrote:
> You say that the solution is brown because CuCl is present diluted in the etchant, and this can only happen when the chloride ion concentration is high, right?
>
> And the way to get the etchant ∗right∗ is to bubble it a lot. Meaning I don't have to add more copper or water? (the etchant works as it is right now, btw)
>
> About the look of the regenerated etchant: You mention deep green, I can see some green going on, at the sides of the tank where etchant has splashed, but the rest of the etchant is dark brown. Is it supposed to be clear in the end or not? If I pick up a drop of it in a piece of paper tissue it stains it green.
>
> Thanks
> Fp
>
>
> ----- Original Message -----
> From: Adam Seychell
> To: Homebrew_PCBs@yahoogroups.com
> Sent: Sunday, April 27, 2003 8:06 PM
> Subject: Re: [Homebrew_PCBs] Home made etchant
>
>
> 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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> >
> >
>
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