C41 PDTA Bleach Recipe

[yoso20]

Kodak made pure Ammonium Ferric PDTA from PDTA, Ferric Oxide and Ammonia, but this was a wild process with lots of heat and pressure. I've tried doing this in my own cabinet (at room temperature, of course), and the Ferric Oxide never dissolved even after years.

Within amateur means you need PDTA, FeCl3 and Ammonia, and you will create a mix of Ammonium Ferric PDTA and Ammonium Chloride. The Ammonium Chloride won't really hurt your bleach.

Ah I see.

For the first recipe, can you confirm this is the correct CAS#?

PDTA - 1939-36-2
2,4-Dihydroxybenzophenone - 131-56-6

 

[koraks]

PDTA - 1939-36-2

Yes

2,4-Dihydroxybenzophenone - 131-56-6

I don't see this in any of the formulae. Which one are you referring to?
I understand this compound is used as a UV filter with a cutoff at 398nm. I don't really see how it would be used in a C41 developer.

 

[yoso20]

Yes


I don't see this in any of the formulae. Which one are you referring to?
I understand this compound is used as a UV filter with a cutoff at 398nm. I don't really see how it would be used in a C41 developer.

1.) Kodak Bleach III for C-41 RA process. This is a very concentrated and fast acting version (RA means rapid action) and was published in the patent US6649331:

PDTA 113.6g
2,4-Dihydroxybenzophenon 0.95g
Acetic Acid 80% 64.4 ml
NH4Br 94.67 g
Fe(NO3)3 * 9 H2O 136.93

 

[koraks]

I see it now; thanks. when you referred to the 'first formula' I thought you meant the first formula posted in this thread. It is actually the first formula posted by Rudeofus in post #4.

 

[Rudeofus]

I don't see this in any of the formulae. Which one are you referring to?
I understand this compound is used as a UV filter with a cutoff at 398nm. I don't really see how it would be used in a C41 developer.

This is about bleach, not color developer, although it may have something to do with color developer after all.

You may remember the ancient discussions of Microdol vs. Microdol-X, in which the latter one contained some "anti staining compound" to avoid the dichroic fogging problem. Decades of guessing and conjecture ensued, two Kodak patents for such "anti staining compounds" were discovered, one of them Benzophenone, the other one 4-Chloro-Resorcinol. At some point the community settled with "4-Chloro-Resorcinol", and I vaguely remember PE being behind this info.

What I do know is the following: In old times Metol contained a PPD impurity, and PPD without a secondary developer is liable to produce dichroic fog. A decent coupler would quickly scavenge oxidized PPD and thereby avoid the issue. 4-Chloro-Resorcinol is one such coupler, and it yields a well soluble product with oxidized PPD, so this may have well been the reason behind its inclusion in Microdol-X. Note, that this paragraph is my conjecture and not backed up by any credible info.

To come back to the Benzophenone, this was the other compound patented by Kodak to address the dichroic fog problem of Microdol. If it works the same way, then it would scavenge carry over color developer, which would otherwise quickly be oxidized by the ferric PDTA and could potentially stain the film. So this compound could be there for this reason. Again, all amateur level conjecture, no real info from Kodak or real chemists.

I have never seen staining effects with my own ferric PDTA bleach, but compared to what Kodak has seen I have seen pretty much nothing. They surely didn't add this compound just for fun, but the cases where it is really needed may be rare or extreme or both. If you indeed have this kind of staining (some people reported it here when going from C-41 CD directly to Tetenal's BLIX), then a stop and brief wash between CD and bleach is just as effective and likely much cheaper than this Benzophenone compound could ever be.

 

[roundcloud]

Kodak made pure Ammonium Ferric PDTA from PDTA, Ferric Oxide and Ammonia, but this was a wild process with lots of heat and pressure. I've tried doing this in my own cabinet (at room temperature, of course), and the Ferric Oxide never dissolved even after years.

Within amateur means you need PDTA, FeCl3 and Ammonia, and you will create a mix of Ammonium Ferric PDTA and Ammonium Chloride. The Ammonium Chloride won't really hurt your bleach.

Is it possible that Kodak uses PDTA, ammonia, and iron nitrate, but the MSDS indicates Ammonium Ferric PDTA because reverse testing is not possible.

 

[halfaman]

Is it possible that Kodak uses PDTA, ammonia, and iron nitrate, but the MSDS indicates Ammonium Ferric PDTA because reverse testing is not possible.

Better to use the past tense like Rudeofus, Eastman Kodak doesn't manufacture photochemicals since very long time ago. Companies like defunct Tetenal or current Photo System purchase ingredients and mix them according to a recipe. Synthesis is done by chemical companies normally in Far East plants.

 

[MattKing]

Better to use the past tense like Rudeofus, Eastman Kodak doesn't manufacture photochemicals since very long time ago.

This isn't quite true, as there still is some "production" of motion picture chemicals - see here: https://www.kodak.com/en/motion/home/.
And in particular:

And specialty chemicals in general: https://www.kodak.com/en/advanced-materials/product/specialty-chemicals/

 

[halfaman]

Well

This isn't quite true, as there still is some "production" of motion picture chemicals - see here: https://www.kodak.com/en/motion/home/.
And in particular:
View attachment 387989


And specialty chemicals in general: https://www.kodak.com/en/advanced-materials/product/specialty-chemicals/

Well noted.

 

[Rudeofus]

Is it possible that Kodak uses PDTA, ammonia, and iron nitrate, but the MSDS indicates Ammonium Ferric PDTA because reverse testing is not possible.

Many years ago, and my memory may be weak on that, PE told me that Kodak used pressurized vats of water, Ferric Oxide/Hydroxide, EDTA/PDTA and Ammonia to make Ammonium Ferric EDTA/PDTA. They thought like chemists and always created pure single compounds and then products from those. I remember once suggesting, that one could put excess sulfite into the HQ+H2O2 mix to make HQMS plus some sulfite, which is needed in E-6 FD anyways, and he was almost angry at the suggestion.

 

[roundcloud]

多年前，我的记忆可能很弱，PE告诉我，柯达使用了加压的水桶，氧化铁/氢氧化铁，EDTA/PDTA和氨水来制造eDTA铵EDTA/PDTA。他们像化学家一样思考，总是创造出纯单一化合物，然后从这些化合物中产生产品。我记得曾经暗示过，一个人可以将多余的亚硫酸盐放入HQ+H2O2混合物中，以制造HQM和一些亚硫酸盐，无论如何在E-6 FD中都需要，他几乎对这一建议感到生气。

ok，thks！