A Kodak bleach, process E-6 Part A and B question

[carerre]

Hi all, I got a bottle of Kodak bleach process E-6 Part A but missing Part B and it is no longer sold. I pressumed that it is already phased out long ago. This Part A has to be long expired. Is there still any use for it or toss?

 

[koraks]

I bet that still works. Part B is probably the pH buffer and likely consists of mostly acetic acid/acetate. In your place I'd try to turn that it into a working C41 or E6 bleach by dialing in pH to whatever it's supposed to be; probably around 5 or so.

 

[carerre]

I bet that still works. Part B is probably the pH buffer and likely consists of mostly acetic acid/acetate. In your place I'd try to turn that it into a working C41 or E6 bleach by dialing in pH to whatever it's supposed to be; probably around 5 or so.

Thanks for your quick response. I am a chemistry noob. What to add to move the scale up or down.

 

[Donald Qualls]

Low pH is acid, so to get from neutral (pH 7) to the presumed pH 5 target, you'd need to add something acidic. High concentration acetic acid is common for darkroom use, but for photographic bleach sulfuric acid (sold as high power drain cleaner in home improvement stores) would also work. You'd use a titration process, adding a little acid and checking pH, until you're close to your target. Pure acetic acid has a pH close to 5, though, so if that's the target for your bleach, you'll probably need something stronger. Do read up on safe use of strong acids before buying or using the concentrated sulfuric sold as drain cleaner, though...

Complicating this is that most photo chemicals that need to be close to particular pH value contain a "buffer" system -- an acid and alkali working against each other to keep the pH in a small range even if other stuff gets into the mixture. We don't (AFAIK) know what the buffering system was for this E6 bleach, so we'd be guessing.

 

[koraks]

We don't (AFAIK) know what the buffering system was for this E6 bleach, so we'd be guessing.

No, I don't know; I'd expect/guess it's probably an acetate buffer system since this is what you typically see (err....smell) in photographic bleaches and bleach-fixes. I'd be inclined to add some acetic acid, then a teaspoon full of sodium hydroxide and then go up or down in pH with hydroxide (solution) resp. acetic acid, using pH indicator paper to get close to 5-ish. There may be documents of this chemistry around that list the target pH; this should help, as would an SDS/MSDS which will probably give a good hint as to the buffer system used.

What to add to move the scale up or down.

The simplest approach would be to get some acetic acid (cleaning vinegar works in a pinch and is relatively safe to work with) and some pH indicator paper. Then dilute some of the bleach; something like 1 part of the part A you've got to 1 or 2 parts water is a reasonable guesstimate. Measure the pH; I expect it'll be between 5 and 7. Then add acetic acid while stirring, periodically checking pH and bring it down to something like 5 or 5.5. If you do it this way, make sure you check the pH every next time you use the same batch of the bleach as it'll probably drift.

This is just off the top of my head; some desk research will get you closer and maybe someone can chime in who has easy access to the required information.

 

[carerre]

No, I don't know; I'd expect/guess it's probably an acetate buffer system since this is what you typically see (err....smell) in photographic bleaches and bleach-fixes. I'd be inclined to add some acetic acid, then a teaspoon full of sodium hydroxide and then go up or down in pH with hydroxide (solution) resp. acetic acid, using pH indicator paper to get close to 5-ish. There may be documents of this chemistry around that list the target pH; this should help, as would an SDS/MSDS which will probably give a good hint as to the buffer system used.



The simplest approach would be to get some acetic acid (cleaning vinegar works in a pinch and is relatively safe to work with) and some pH indicator paper. Then dilute some of the bleach; something like 1 part of the part A you've got to 1 or 2 parts water is a reasonable guesstimate. Measure the pH; I expect it'll be between 5 and 7. Then add acetic acid while stirring, periodically checking pH and bring it down to something like 5 or 5.5. If you do it this way, make sure you check the pH every next time you use the same batch of the bleach as it'll probably drift.

This is just off the top of my head; some desk research will get you closer and maybe someone can chime in who has easy access to the required information.

ThankU guys. At least there is hope.

 

[Rudeofus]

There are four basic ingredients to an E-6 bleach for 7 bath process: Ammonium Ferric EDTA (oxidizer), Ammonium Bromide (counter anion), pH setter and some excess EDTA. It is not clear, which bleach part contains which, except that the deep red liquid part certainly contains the Ammonium Ferric EDTA and quite unlikely the pH buffer. An MSDS I saw for part B mentioned just the EDTA, maybe they used the EDTA mix with different number of alkali to set pH. It would still surprise me, if that part B didn't contain Ammonium Bromide, although the MSDS doesn't mention it.

You may have to experiment a bit, and the raw chems needed may end up being more expensive than new bleach. You'll likely learn a lot in the process, though.

 

[koraks]

It is not clear, which bleach part contains which

No, although maybe the both of us should have read the label a little better. I did, but stopped after the first line, which was silly...

Note that this contains the ammonium ferric EDTA, but EDTA as such is not mentioned. It does contain ammonium bromide as well as hydrobromic acid (an interesting way to add both an acid and bromide!), so it seems what's lacking is mostly the other part of the buffer, which would likely be an alkali (and perhaps some additional acid).

 

[Rudeofus]

No, although maybe the both of us should have read the label a little better. I did, but stopped after the first line, which was silly...
View attachment 396199
Note that this contains the ammonium ferric EDTA, but EDTA as such is not mentioned. It does contain ammonium bromide as well as hydrobromic acid (an interesting way to add both an acid and bromide!), so it seems what's lacking is mostly the other part of the buffer, which would likely be an alkali (and perhaps some additional acid).

Wow. So they basically used the recipe from Kodak's E-6 5l kit, and just left out the buffer. BTW all these polyacetic acids (like EDTA) are very good buffers over a wide range of pH, so just having a suitable EDTA mix in the second bottle sounds interesting.

In this case, the OP can proceed as follows: find a cheap source of Na2-EDTA or Na4-EDTA, add about 2 g/l to bleach working solution. If OP doesn't have a pH meter, OP can use fizzle test with bicarbonate to set pH.

 

[carerre]

Wow. So they basically used the recipe from Kodak's E-6 5l kit, and just left out the buffer. BTW all these polyacetic acids (like EDTA) are very good buffers over a wide range of pH, so just having a suitable EDTA mix in the second bottle sounds interesting.

In this case, the OP can proceed as follows: find a cheap source of Na2-EDTA or Na4-EDTA, add about 2 g/l to bleach working solution. If OP doesn't have a pH meter, OP can use fizzle test with bicarbonate to set pH.

Wow. U guys are amazing. I happened to have Na4-EDTA ThankU!

 

[Rudeofus]

If you need a rationale for the extra EDTA: look for British patent GB991412A.