Quote Originally Posted by Kevin Sullivan
Sorry, thought I was done but this was too tempting...
And since you want to talk science, where did you publish the finding about the change in chemistry with the addition of oxalic acid? Was this run through a mass spectrometer? Green, yellow,.

Uhhhm, where to start, Eric. This is basic chemistry. No need to publish it in a fancy journal. And a x-ray mass spectrometer will usually only tell the amounts of pure elements (how much oxygen, iron, hydrogen etc.) not necessarily how those elements are arranged. (FO or oxalic acid, h20, etc.) Also, gas spectrometers don't work because the FO breaks down before it reaches a gaseous state.

I can fax you the chart Dr Howard Efner drew for me that explains it quite well, he seemed to think the whole thing was organic chem 101 level basics. I don't think the chem journals are that interested in this level of redundancy.

Ole even mentions it, in a round about way, here:



The concept is that the wild tangled arms of the FO can be neutralized with the addition of oxalic acid. The oxalic grabs on to these loose arms and straightens them out, and they can no longer bond to each other as easily. This actually changes the non-stoichiometric FO into a stoichiometric compound, because the FO atoms are bound with oxalic, they can no longer randomly clump together. Now they have a more or less fixed structure. This is why adding oxalic acid to pure FO cause a color shift from muddy yellow brown to the bright emerald green. Its the shift from non-stoichiometric to stoichiometric with the addition of free oxalic acid that causes it to turn translucent green. This is well documented and understood, I'm suprised you aren't familiar with this idea.

This is very easy to test visually if you have some pure FO, just keep adding oxalic acid and watch it turn green. I wouldn't say we are chemically changing the FO to something that is not FO, we are simply controlling its form with oxalic acid.

I think that explains it. There's a little more info in the book The New Platinum Print which also includes Rudiak and DMKs prefered formula. (18g Oxalic Acid to 100ml FO#1, whew, way to much for my taste.)

Cheers,
Kevin Sullivan
Kevin, In my basic chemistry courses in college, they didn't discuss ferric oxalate and unfortunately the photography bug was biting at me more than the chemistry bug so I left it before any diuscussion of organic chemistry related to this topic. If the ferric is not changed, that is to a state of not being ferric oxalate anymore, than have those test reveal any loss of speed due to excess oxalic acid? Please send via email or FAX, the chart from Howard. Your use of the term neutralized to me implies that adding more oxalaic acid would slow the speed of that solution. Did you find that to be true?

Not really looking for fancy journals either but if you said it was included in TNPP, that would work : )

I will also readily admit to not having a copy of TNPP but only reviewing it while helping the formulary establish their workshops back in 1999, but I do recall those number from Rudiak and Kennedy only being tested against current (at the time) B&S powder and not against other FO powder on the market.

"Maybe one day some brave PhD student will sort it out, but it's not the path to a shining career", is a quote from one of my emails with Mike Ware on the subject of ferric oxalate.

I shall be happy with mine, but also happy to see your chart from Howard.

Eric