[alt-photo] Re: Fluka / Sigma-Adrich Ammonium Iron(III) Citrate - contains Fe(II)!!!

[John Brewer]

That's interesting Loris. I've just got some from Sigma (UK) and mine is
fine, (used for cyanos and VDB). I wonder if yours has been hanging around a
bit?

John.

-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
Loris Medici
Sent: 27 June 2010 14:19
To: The alternative photographic processes mailing list
Subject: [alt-photo] Fluka / Sigma-Adrich Ammonium Iron(III) Citrate -
contains Fe(II)!!!

Hi all,

I've just purchased Ammonium Iron(III) Citrate from Fluka / Sigma-Adrich.
(See product info here: http://bit.ly/9nrgtj, Lot #BCBB2047)

Unfortunately, as soon as I mix stock soln. A and B ,I get spontaneous blue
in the the cyanotype coating solution. I think this is indication of some
Iron(II) impurity!!! (It's not the ferricyanide, that works w/o problems
with B&S AFC...)

I tried to add small amnt. of OTC 3% hydrogen peroxide in soln. A, in order
to convert Iron(II) to Iron(III) and it worked. (Two drops of peroxide in 10
drops of 25% AFC cures the instantaneous blue problem completely...)

So,

1. Beware if you're planning to purchase that particular product!

2. I'm going to test in order to find the min. amnt. of peroxide that cures
the problem. (Tell me if you want it to share here later...) OTOH, I'm not
sure if there's any adverse effect in adding peroxide to the stock solution,
both in terms of stability and picture-making. I would definitely like to
have your comments and warnings (if any) on this issue. (Please note that
I'm planning to use the same AFC for making Vandykes and/or Argyrotypes
too!) Also, what else can I do to eliminate Iron(II) from the stock
solution?

TIA,
Loris.
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