From: Linas Kudzma (lkudzma@earthlink.net)
Date: 02/07/02-07:38:19 PM Z
Halvor,
This is a very nice recipe you posted. What is happening here is the Ferric
ions (Fe+3) and Sodium ions (Na+1) are exchanging counter ions. This
reaction does not involve oxidizing ferrous (Fe+2) to ferric (Fe+3) as in
methods using concentrated hydrogen peroxide (like the method on Eric
Neilsen's web site). If ferric nitrate is inexpensive and readily
available, the "Dr. Bovins formula" seems like a nice easy method, assuming
that the by-product sodium nitrate that is also formed has no negative
effect. Sodium nitrate is an oxidizing agent and might be (?) a contrast
booster in Pd/Pt processes. For a home lab it is safer to deal with a
solution of sodium nitrate vs. disposing of the nitric acid formed in the
Vicente-M. Vizcay Castro method used by Jeffrey D. Mathias, and described
on Jeffrey's web site.
For those interested, I give the balanced equation of the Dr. Bovins method
with the molar amounts. What you end up with is a 25% w/v solution of
ferric oxalate/water with oxalic acid and a considerable amount of sodium
nitrate also in solution. If this solution works well for Pd/Pt printing,
it would mean the sodium nitrate is just along for the ride and has little
effect. There is no practical way to remove the sodium nitrate. The 1 gram
of oxalic acid in Dr. Bovins formula plays no role in the reaction to form
ferric oxalate. Apparently, it's just added to be present in the final
solution.
Based on the recipe you posted, the composition of the final solution is:
Water 55 ml + 6.9 ml (produced by the reaction)
Ferric Oxalate 15.58 g
Sodium Nitrate 16.49 g
Oxalic Acid 1 g
The balanced equation is:
3[Na2(C2O4)] + 2[Fe(NO3)3*9H2O]
MW 134.00 MW 404.00
13 g (0.097 mole) 26 g (0.064 mole)
= Fe2(C2O4)3*6H2O + 6[NaNO3] + 12[H2O]
MW 483.85 MW 84.00 MW 18.0
15.58 g (0.032 mole) 16.49 g (0.194 mole) 6.9 g (0.38 mole)
I hope this helps. Or maybe everyone is getting tired of Dr. Kudzma's
chemistry lectures?
Linas
> [Original Message]
> From: Halvor <halvorb@mac.com>
> To: alt-photo-process-l <alt-photo-process-l@sask.usask.ca>
> Date: 2/6/2002 9:36:48 PM
> Subject: Regarding Ferric Oxalate
>
> Hi List
>
>
> I have been using this formula for making ferric Oxalate for Platinum
> printing,Its maybe a bit safer / simpler than the Hydrogen peroxide
> variety. Got it from a swedish handbook for alternative processes, where
it
> was called Dr Bovins Ferric Oxalate process.
>
>
> Oxalic Acid C2H2O4*2H2O 1g
>
> Sodium Oxalate C2O4 Na2 13g
>
> Ferric III Nitrate Fe(NO3)3*9H2O 26g
>
> Water 55 ml.
>
> to be mixed in safelight, and in listed order, then given at least 12
hours
> before use.
> This works directly as the ferric oxalate solution in Pt/Pd printing,
> Potassium Chlorate can be added for contrast control.
>
>
> I have not tried any other methodes, and wonder what is the role of this
> solution in the platinum process apart from providing Fe3, do the
different
> methodes for making ferric oxalate give different results in the print ?
Or
> is (From a naive point of wiev) ferric oxalate ferric oxalate ?
>
>
> Halvor Bjoerngaard
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