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

[Loris Medici]

  Dear Christina, just for an example of using molar notation, wherever 
appropriate:

PD (as you state) is actually PdCl2, or maybe PdCl2.2H2O (means it's 
hydrated with 2 water molecules.) I'll assume that what you have on 
hands is the former...

1 mole PdCl2 = 177.33g (See this address: 
http://environmentalchemistry.com/yogi/reference/molar.html. There are 
many more in the web, therefore it's easy to find out this information - 
as long as you know the chemical formula of the compound in question...)

Molarity is weight of compound (g) in 1000ml solvent.

Therefore, the Pd solution you prepare is:
5g PdCl2 / 55ml water (actual figues) * 1000ml / 177.33g (to find 
molarity) ~= 0.51M (rounded)
(1 mole PdCl2 + 2 mole salt makes 1 mole double salt of Pd, therefore 
the molarity of PdCl2 is equal to the resulting molarity of Na2PdCl4 in 
your example; PdCl2 + 2NaCl -> Na2PdCl4)

In Pt/Pd printing, according to the reaction formula, you need 2 moles 
of iron per 1 mole of noble metal. (Won't get into the specifics of 
this; it's well documented in many places - such as Mike Ware's 
wonderful site full of extremely useful information: 
http://www.mikeware.co.uk/mikeware/Iron-based_Processes.html) Therefore, 
your iron solution should be 0.51M * 2 = 1.02M (rounded)

The chemical formula for ferric oxalate is Fe2(C2O4)3.5H2O - as stated 
by B&S, and it makes perfect sense to use their formula if you purchase 
your FO from them, indeed. (See: 
http://www.bostick-sullivan.com/articles/ferriccoalate.html) OTOH, 
please mind that with FO, the composition may change from batch to batch 
and/or supplier to supplier. That's why Mike Ware calls it an "ill 
defined compound" - you can't be sure when it comes to FO... Anyway, 
let's assume we're in the ballpark:

1 mole of Fe2(C2O4)3.5H2O = 465.829g (See the address above to check...)

15g FO to make 55ml = 15g / 55ml = 27.27% = 270g in 1000ml, therefore, 
your FO solution is 272.7g / 465.829g ~= 0.58M

Now, there's something seriously wrong here; we should have come to 
something near to 1.02M for the iron solution - assuming: (a.) The 
formulae aren't correct and/or (b.) Your mixing instructions below don't 
mean "add water to make" but "add x into y ml water" instead and/or (c.) 
The B&S stated formula for FO isn't correct.

Using 0.58M FO for 0.51M Pd means that you actually will never be able 
to use up all the Pd you have put on the paper, because you don't have 
enough (molar equivalent) Fe in the coating solution. (0.58 < 1.02, 
considerably.) Eventually it also means that you'll wash more Pd (than 
what's needed) down the drain...

BTW, the strength of your Na2PdCl4 solution is: 0.51M * 294.21g (molar 
mass) / 1000ml (according to the definition of molarity) = 15%. In other 
words; less than Terry's 20% - which means he is actually washing more 
of the precious metal down the drain, relatively - especially so if he 
indeed uses 20% FO (< your 27%) as he stated in his last message...

You may not care for the extra wastage if you're getting good 
"pictures", or you may care - that's up to you.

It's very late now, and I'm sure someone will correct me if I'm making 
an "doubleplushorrible" mistake here...

Regards,
Loris.


22.07.2010 20:51, Christina Anderson yazmış:
> ...
> Next question though, as Terry/Loris' discussion has called to mind percentages.
>
> My standard PT is 10g/50ml
> My standard PD is 5g/3.5g sodium chloride/55ml
> My standard ferric is 15g/1g oxalic acid/55ml
> My Na2 Sodium Chloroplatinate I get from B&S, as a 20% and mix it to 5%.
>
> So I am not using a 20% palladium. Do you all use 20% palladium as does Terry?
...