Well, other than adding copper to it in PCB etching, ferric chloride
is used as a flocculant and filtration aid in drinking water treatment.  It
removes things like arsenic and manganese at treatment plants.
(http://www.pvschemicals.com/techMSDS/PotableTech.doc)


<here comes a joke>
Also, if you don't want to etch with it, you can always sell it as a health
supplement.
(http://www.helpuniversity.com/health/A/Anhydrous-Ferric-Chloride-Msds.html)
I HOPE that site is a hoax.  There's some scary
stuff on the internet.  FeCl3 as a styptic tincture yes, but as a pill for
ingestion? NO! Not that I've ever heard of, anyway.
<there went the joke, and a slightly frightening one, at that>

But, once the cupric chloride is in (after PCB etching) you have to
precipitate the copper chemically/electrochemically before dumping it.
The landfill is better than the sewer system in my opinion because it's
harder for leaching from landfills to return to the water system.  It's a
good idea to neutralize it before putting it in the ground too (use iron to
precipitate out the copper, then neutralize with baking soda (NaHCO3)).

Gustaf

> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of Jim Franklin
> Sent: Monday, March 01, 2004 7:20 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: ] My first PCB production
>
>
> I followed that link,
>
> "..Two pounds of root killer contain 0.5 pound of pure elemental copper
> enough to contaminate 20 million gallons of water..."
>
> It makes you think, doesn't it when you see those kinds of numbers...
>
> Jim
>
> -----------------------------
>
> -----Original Message-----
> From: pic microcontroller discussion list
> [mailto:PICLIST@MITVMA.MIT.EDU]On Behalf Of William Chops Westfield
> Sent: 01 March 2004 23:15
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: ] My first PCB production
>
>
> On Monday, Mar 1, 2004, at 13:54 US/Pacific, Spehro Pefhany wrote:
>
> >
> > But my wife, who is an expert in wastewater and other environmental
> > technical and legal matters, thinks a bit down the home drain with lots
> > of water isn't a technical problem.
> >
> >
> Note that in the US, it is relatively common (or WAS relatively
> common, anyway) to dump a couple pounds of copper sulfate down
> your toilet to kill roots that might have been invading your
> underground pipes.  Or something.  (Not that everyone is happy
> with this: http://www.city.palo-alto.ca.us/cleanbay/pdf/root.pdf )
>
> Copper sulfate is also pretty widely used as an agricultural
> fungicide.
>
> If you get up to several ounces of copper per year (at 1oz per
> square foot of typical PCB, so, serveral square feet of finished
> PCBs), you should probably start thinking about being nicer than just
> flushing your used etchant down the drain.  But that's a awful LOT
> of PCBs for the average hobbyist...
>
> BillW
>
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