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

[Christina Anderson]

Loris,

OH PHEW. Yes, I was panic stricken, as much about the waste of precious metals as about the potential mistaken formula in my alt manual that I've been doing/teaching this last decade. Now I can breathe easy. I always HATE putting stuff in print because once an error is there, it is chiseled in stone. My chromo article has an error of formula (egregious) where the article writes it as 25ml of Tektol when it should be 125ml of Tektol. ARRRGGGH. (What is even weird is in the proof copy I got from Photo Technique the mistake was not there).

I do mix my own pd- (it is quite a bit darker/richer brown than the B+S palladium which I've never figured out why). 

 I do not mix my own FO nor NA2. 

My students buy the kits from B+S.

I don't have a problem with solarization, though my students do occasionally when they are stingy with the solution.

But I agree that the molarity is a very intriguing subject and feel that it translates to all these processes well, including my experiences with cyanotype.

I do come at alt from a different perspective, what I call the "kitchen" perspective.  Essentially mix a tsp of this or a gram of that into a measure of water. I have an accurate gram scale and then translate that into tsp/tb for the students.  I can safely say that NONE of my college students possess a gram scale of their own. IF I start out with the easy stuff they're much more liable to enjoy the processes. There's time and interest later for some of them to get into the finer nuances of alt, and that should happen more as the dangling carrot of Christopher James' alt friendly MFA comes into fruition. 

But the kitchen perspective I work from doesn't exclude fascination with moles.
Chris

Christina Z. Anderson
christinaZanderson.com

On Jul 23, 2010, at 6:43 AM, Loris Medici wrote:

> Christina, it's OK, it's OK- don't panic! ;)
> 
> I was kindly made aware of the mistake I did yesterday night. (I knew there
> was something seriously wrong in the result!) See below:
> FO has two Fe atoms (see the formula below) in the molecule, therefore, I
> had to double the the FO concentration in order to find the Fe
> concentration, which makes 2 x 0.58M = 1.16M. Eventually, 15% Na2PdCl4
> (0.51M) or 20% Na2PtCl4 (0.52M) are both well balanced with 0.58M FO (~27%),
> in other words 2x 0.58M FO - > 1.16M Fe. (With a little excess of Fe, which
> is perfectly acceptable...)
> 
> My confusion arose by the fact that I'm very much used to AFO (because
> that's what I print with), which has only on Fe atom in its molecule,
> therefore Fe concentration = AFO concentration. Again, with FO,
> concentration of Fe = 2x concentration of FO - as explained above.
> 
> Anyhow, I think this still *a good example to demonstrate when and how
> molarity is useful.* (See below...)
> 
> Terry, your 20% FO strength is definitely considerably weaker than what you
> need for both 20% Na2PtCl4 and 20% Na2PdCl4 - moreso in case of the latter.
> In order to get even better results and/or cut down costs / prevent
> unecessary wastage, you'd better:
> 1. Increase your FO solution strength to 27%, and
> 2. Decrease your Na2PdCl4 solution strength to 15%... (Your Na2PtCl4 is OK,
> at 20% - if it's the Na variant of the salt.)
> 
> Do you see how this "over-complicated" unecessary dissection proved very
> useful / helpful to you?
> 
> Regards,
> Loris.
> 
> 
> -----Original Message-----
> From: Loris Medici [mailto:mail at loris.medici.name] 
> Sent: Friday, July 23, 2010 1:32 AM
> To: The alternative photographic processes mailing list
> Subject: Re: [alt-photo] Re: dilution of pt/pd
> 
> 
> ...
> 
> 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
> 
> ...
> 
> 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,
> 
> ...
> 
> It's very late now, and I'm sure someone will correct me if I'm making an
> "doubleplushorrible" mistake here...
> 
> _______________________________________________
> Alt-photo-process-list | http://altphotolist.org/listinfo