Re: [ATM] Stripping to re-figure?

[Mark Holm <mdholm@telerama.com>]

Mark Holm wrote:

> Without knowing the concentration of ferric chloride in circuit board
> etchant, I can't calculate how much vitamin C one would need to reduce
> it all.  Anybody know what that concentration typically is?

Answering my own question, with the help of Google, it appears that
typical ferric chloride etchant has a density of 42 degrees Baume, which
is 1.408g/ml.  Thanks to a table of solution density vs. concentration
for ferric chloride at the Mettler-Toledo web site, that can be worked
out to 0.553 grams of anhydrous FeCl3 in each ml of solution.  A little
work with molecular weights gives 0.601 grams of ascorbic acid (Vitamin
C) needed to reduce the ferric chloride in one milliliter of etchant to
the ferrous oxidation state.

Once you have your iron down to ferrous, you need have no environmental
qualms about pouring it down the drain.  Just don't pour it into your
stainless steel sink.

This is for the extremely environmentally conscious.  Personally, I
think a small amount of ferric chloride down the drain is harmless
environmentally.  Here in Pennsylvania, we commonly have acid seepage
from old coal mines, or natural seepage from unmined coal seams.  This
stuff is full of ferric iron.  In large amounts, it is bad news for the
health of a stream, but small amounts do little harm.


-- 
Mark Holm
mdholm@telerama.com

_______________________________________________
ATM mailing list http://www.atmlist.net/