OK, I'm a little behind on my Orchid. I'll put in my .02 worth.
Ferric chloride can be reused many times, adjusting the strength up
or down with either anhydrous (dry) crystals or distilled water.
However, for the saved mordant you intend to use again, you do want
to decant (pour) the liquid from the container, leaving behind the
smut (sludge) in the container so it doesn't interfere with
As many people have pointed out, it will etch stainless sinks and
copper pipes, as well as aluminum, steel of any kind, copper, zinc,
chrome, and a few other metals I've forgotten. It will not etch
silver or gold, which is useful if you happen to be working with
To dispose of that sludge, it's best to contact your local sanitary
landfill, as different states have different procedures, and
sometimes one county to the next will have a different procedure.
In my area, after neutralizing the sludge with an alkaline solution,
the sludge is mixed with a little cement, sand and water, to make a
mortar encasing the sludge, along with its bound etched metal, and
then it is buried in the soil. I was told, because of it being mixed
in this manner, it will break down very slowly into the various
components of iron, chlorine, and the etched metal. It wasn't the
ferric (iron) or chlorine (chloride) that is the problem, as it is
the etched metals that can cause toxicity in the soil or water if
dumped freely. I still suggest you call your local landfill for
proper disposal in your area.
Believe it or not, ferric chloride was used many years ago to treat
pernicious anemia. The palms were painted with the solution, because
the size of the palm was relative to the patient's size and correct
dosage. I don't know what the strength of the ferric chloride was. It
is readily absorbed into the skin, which is why certain people should
not use ferrics at all. Those with thasselemia, compromised immune
systems (like cancer patients, etc.), liver problems, or pregnant
women, should not be around ferrics.
I hope this helps.