--- In
Homebrew_PCBs@yahoogroups.com, "dl5012" <dl5012@...> wrote:
>
> Hi,
>
> Glad you rang in on this topic...
>
> What is the proper way to dispose of used ferric chloride? Is there
> a way to rejuvinate it? Someone mentioned adding sulfuric acid, but
> everyone is imprecise about ratios.
No, not Sulfuric Acid; use Hydrochloric Acid instead. As for how
much, the appropriate amount is some.
> Is there a simple way to
> determine how much life is left in the etching solution?
When it starts taking too long to etch, there's not enough life
left.
> Is there
> an inexpensive way to precipitate the copper out of the solution and
> end up with just ferric chloride?
I once tried electroplating out the Copper (Carbon cathode, Iron
anode). It sort of kind of worked (I ended up with Copper crystals
on the cathode.), but I don't remember if the resulting solution
was any good for etching or not (or, whether I even tried it). My
intent was to remove the Copper and replace it with something less
biologically nasty than Copper. Maybe if we have an electro-chemist
in the house, he can advise on such a procedure (Beware of
outgassing Chlorine gas if you try such a procedure!).
> I'm hesitant to use some of the other recipes. I've used ferric
> chloride for many years and my main concern was not breathing the
> chlorine gas that gets released. Now, that I'm more environmentally
> aware, I want to know how to dispose of it properly. An old bottle
> I had from Radio Shack said to put it down the toilet. I'm sure
> that's not a good thing to do these days...
Actually, Ferric Chloride isn't that bad (It's been used as a
nutritional supplement in it's food grade form.). Unfortunately,
used solution has a lot of Copper Chloride in it, which is deadly
to most biological organisms.
> Regards,
> Dennis
Dave