[alt-photo] Re: dilution of pt/pd

[Loris Medici]

See comments/replies in between quotations below...

-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org On Behalf Of
Christina Anderson
Sent: Friday, July 23, 2010 3:22 AM
To: The alternative photographic processes mailing list
Subject: [alt-photo] Re: dilution of pt/pd

> From what I am gathering, below, I am using twice as much metal as I need
in comparison with the FO you are saying.
> Put another way perhaps, I am not using enough FO to reduce the metal that
I am coating on the paper, correct?

Yes, if I'm not mistaking that is...

> Looks like you have taken into account the extra salt in the pd, did you
also take into account the oxalic acid in
> the FO?

I've taken the extra salt in Pd into account because it was needed to
calculate the % strength of the final / actual compound in question =
Na2PdCl4. I haven't taken the extra oxalic acid in the FO into account
because - to my knowing - it doesn't do anything in reduction reaction.

> Yes I do care about the extra waste, and if you are certain that the ratio
of moles should be 2 moles iron to
> 1 mole metal, then I have two choices it seems--to raise the amount of FO
I use at time of coating or mix a
> weaker PD. Now that should save some $$.

Regarding 2 Iron : 1 Noble metal; see Mike Ware's article; that's exactly
what I understand from it.

Regarding saving $$; exactly! If I were in your place I'd opt / go for
mixing a weaker Pd solution, maybe a small amnt. - such as 10ml - to see
what happens. (Don't forget to lower the salt content accordingly, BTW...)
You've been satisfied with what you could get, right?

0.58M FO matches with 0.29M Pd,
0.29M PdCl2 = 0.29M * 177.33g ~= 51.4g (in 1000ml) ~= 51.4g * 55ml (target)
/ 1000 (by definition) ~= 2.8g (in 55ml.)
Even if you use 3g (in 55ml, 6-7% extra - for safety & ease in measurement),
that would be 1 - (3/5) = 40% less Pd!!!

> Interesting, too, that even though my PT is referred to as a "20%" (10/50)
it is actually only 15%.

No, your Pt is indeed 20% if you're using B&S Pt Soln. #3...

Now, the reason for a stronger Pt soln. could be due the fact that it has
less covering power compared to Pd... I'd definitely opt to extend the
solution with water (in order to facilitate coating), instead of using extra
"precious" noble metal "which - theoretically, won't have the chance of
being reduced!"

Regards,
Loris.