Can I mix Ammonium ferric sulfate and EDTA Acid to form Ammonium ferric EDTA?

[RealJohn]

Futher, can I use potassium dichromate + sulphric acid as c41 bleach?

Thank you very much for your help.

 

[Rudeofus]

If you mix Ammonium Ferric Sulfate with EDTA free acid, your pH will go way down to the point where EDTA will no longer dissolve. Be prepared to add Ammonia to make this work. You still end up with left over Sulfate ion, which is an anti swell agent and will slow down bleaching (you are trying to make a bleach for color film, yes?). If you can get your hands on it, use Ferric Nitrate.

C-41 process is rated for very weak bleaches based on Ammonium Ferric EDTA and the slightly stronger Ammonium Ferric PDTA. Many people have reported success with Ferricyanide, but YMMV. I see no reason why you would use the toxic&carcinogen and hard to get Dichromate for this purpose. Unlike B&W reversal processing you don't have to care about retaining all the silver halide in your film.

 

[RealJohn]

Thanks for your advice.
So 1g Ferric Nitrate + 1g Ammonia + 1g EDTA = how many grams of Ammonium Ferric EDTA?
Yes, I want to make my c41 bleach and my preference is Ammonium ferric EDTA as Kodak does.
I ask about Postassium Dichromate beacuse I have it on hand for b&w reversal bleach. I wear face mask and gloves when doing b&w reversal so I think I would apply the same safety precautions to c41 process too.

 

[Rudeofus]

So 1g Ferric Nitrate + 1g Ammonia + 1g EDTA = how many grams of Ammonium Ferric EDTA?

Watch out for molar weight, and use a pH meter to fine tune your bleach. Look at MSDSs for correct values and likely ingredients.

Yes, I want to make my c41 bleach and my preference is Ammonium ferric EDTA as Kodak does.

Please be aware that Kodak's most recent C-41 bleach uses the more powerful Ammonium Ferric PDTA, not Ammonium Ferric EDTA. In case you need it, US patent application US20040126716A1 provides a full set of official formulas for C-41.

 

[Photo Engineer]

Do NOT use the dichromate bleach on color films. It is too acidic.

And Kodak uses an expensive reactor to turn Ferric Oxide and Ammonia plus EDTA to form FeNH4EDTA directly. Now they use PDTA to clear the silver in most recent films.

And, they do not use a blix for film as it is too weak in general.

PE

 

[RealJohn]

Thanks Rudeofus and Photo Engineer.

According to the US patent (there was a url link here which no longer exists) article, Kodak uses 113.6 gram PDTA. Can I directly replace PDTA to EDTA? There is a chemical store near my workplace provide EDTA in small quanity (500g). PDTA seems even more difficult to get in small batch.

PDTA mass 314 gram
EDTA mass 292 gram

314/292x113.6 = 122.2 gram
Am I correct?

If finally I cannot make Ammonium ferric EDTA bleach, then I will switch to Ferricyanide bleach

 

[Photo Engineer]

Switch to Ferricyanide.

Use this process cycle: Dev, clear/stop, wash, ferri bleach, wash, fix, wash, stab or final rinse. The clear / stop is a bath of Acetic Acid + Sulfite.

PE

 

[Rudeofus]

According to (there was a url link here which no longer exists), US patent 6720134 by Fuji contains the official formulas for E6. Since E6 uses a bleach based on Ammonium Ferric EDTA, you could use this as a starting point. The recipe assumes that you already have Ammonium Ferric EDTA as base substance, so you have to find the correct ratio of compounds if you start with EDTA and some ferric salt.

Photo Formulary sells Ferric Nitrate, which is the compound you want to use for this, because then you don't need to explicitly add the hard to get Ammonium Nitrate.

PS: One more thing: Bleaches based on Ammonium Ferric EDTA must be a lot more concentrated that those based on Ammonium Ferric PDTA. You can therefore not directly substitute one for the other.

 

[Athiril]

Ftr, I've had a rehalenogating dichromate bleach before.


Anyway potassium ferricyanide is preferred, cheap and easy. Copper sulfate works too, but even washed properly the colour balance/filtration for the same look is a bit different.


I've used the dichromate + sulphuric acid bleach on E-6 film before, but that was so I could remove the negative prior to colour development so I could rehal process the colour step to intensify the slide.

 

[RealJohn]

OK, thanks all comments.