RE: Regarding Ferric Oxalate

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From: Halvor (halvorb@mac.com)
Date: 02/07/02-10:41:03 PM Z

Dear Dr. Kudzma

you might have exhausted this lists patience, however I am new here and all
ears, would like a few more lectures if you don´t mind :)

First I am not a chemist, but are trying to learn.

Now, The recipie I posted was as it is written in the book I have. And is
working fine as it is. However, as I have understood it the ratio between
Ferric Nitrate and Sodium Oxalate in this recipie is 1 part Fe to 1,5 part
Sodium Oxalate( 0.097 mole / 0.064 mole = 1,5). Ferric Nitrate should have
(as I have been explained) capacity to react with a ratio of 1 to 3 (6 to 2
electrons). I have tried to mix this, but the highest ratio I can mix is
about 1 to 2,5 any more Sodium Oxalate and it precipitates. I was also told
to maintain the ratio between Oxalic acid and Sodium Oxalate, and have done
so. If, as you say here, oxalic acid plays no part in the reaction I will
try a new mix with the original amount of OA (and without OA). I have
tested this with Palladium printing and the 1 : 2,5 solution seems to give
a slight increase in sensitivity, (about 0,15 Lg H) density stays the same,
exsposure range increase, and gamma drops as a result. I should however do
a few more tests before I trust these results.

Any comments ?

For the sodium nitrate and contrast, I have only used this recipie and can
not compare, but generally it is producing an ansi contrast of about 0,7
(to 0,8) with Pure Palladium. My results are a bit inconsistent though.
(meaning sometimes the print goes completely brown, and density drops to
about Lg 1 ??? anyone)

What is the role of Oxalic acid in Pt/Pd printing. I have seen other people
on this list talking about giving the paper a dip in a 1 % OA solution. Is
this recipie a sort of simpler way of doing this ?

Thanks

Halvor

Linas Kudzma said at ÒRE: Regarding Ferric OxalateÓ.
[2002/02/08 10:38]

> 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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