From: Linas Kudzma (lkudzma@earthlink.net)
Date: 02/08/02-08:03:50 AM Z
Halvor,
In the recipe you posted the ferric nitrate and sodium oxalate are in
exactly the correct ratio to fully react. If you look at the balanced
equation you see that they react in a 3:2 molar ratio. If they were mixed
in any other ratio, some ferric nitrate or sodium oxalate would remain in
the final solution. The oxalic acid may help solubility, or provide other
less understood benefits to Pd/Pt printing. I'm not at all sure what role
it plays. However, oxalic acid seems to be a useful additive in ferric
oxalate solutions for Pd/Pt.
I will be away from the computer for a few days. We can further discuss
this privately, or on the list, when I return.
Linas
> [Original Message]
> From: Halvor <halvorb@mac.com>
> To: alt-photo-process-l <alt-photo-process-l@sask.usask.ca>
> Date: 2/7/2002 11:41:03 PM
> Subject: RE: Regarding Ferric Oxalate
>
> 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=B4t 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 =3D 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 =D2RE: Regarding Ferric Oxalate=D3.
> [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)
> >
> >
> > =3D 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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