D-72 modification

[kevin klein]

I have the chems for making D-72 that I got a few years ago, the Metol is turning a greyish brown. I am going to try a mix without it to see what happens. What is the Metol for in the mix? Also, what does the Potassium Bromide do?

 

[Photo Engineer]

Without Metol, the contrast will probably be low and without KBr, the fog might be high. This would vary from paper to paper and from actual formulation to your final formula.

PE

 

[desertrat]

I have made up some developers with old metol that had been stored a long time and was turning slightly dark. The developers worked fine.

 

[kevin klein]

I used it lastnite and it worked fine. As long as the metol still works if it is discolored I will be happy.

 

[trendland]

I used it lastnite and it worked fine. As long as the metol still works if it is discolored I will be happy.

Old metol (powder) in bw develloper?
I have bought some different boxes
ILFORD PERCEPTOL on Ebay.

The design of the packages and the original old shields prices have shown
the years.
Because of the dates of the years between 1980 - 1986 I was realy surprised about this older stuff.
As you know ILFORD has packed metol
seperately in Perceptol - I saw no risc.
So I was actual.
Like new produced Perceptol to 1/7 of
todays price list.
The chemicals reaction of raw chemicals
(as powder) should be so slow with good
storing that it is in the very most cases
FOR DECADES storable.
Whow - regarding the livetime of liquid
bw deveolper kits.
2 Years - as recomanded (unopened).
The real livetime should be (in most cases) x 2 - x 3 then it will become to a
end. Ok - there may be examples of 10 years but I doubt a little to this.
EXEPTION - RODINAL of cause.

with regards

 

[Ome Kees]

I use phenidone as a substitute at a ratio of 1 to 10. Much cleaner and works just the same as metol.

 

[Anon Ymous]

... the Metol is turning a greyish brown...

Sorry for being off-topic, but this thread got me curious and the chemists in this forum might have something to say. Could we use activated carbon to purify discolored developing agents? I was thinking about a solution of the developing agent in a suitable, volatile solvent, where activated carbon is added. After filtration and evaporation we could get the recrystalised agent back, theoretically in a purer form? Would it work, or would it be a waste of time and resources?

 

[Photo Engineer]

Yes, activated charcoal is a common purification method for many chemicals, but in this case, you have to contend with aerial oxidation and thus you might end up where you started or worse.

PE

 

[Anon Ymous]

Thanks PE.

 

[Photo Engineer]

No problem. I've contended with this type of situation many times. Sometimes you have to do it under nitrogen or other inert gas. It is not straightforward to purify strong reductants in an oxidizing atmosphere.

PE

 

[nworth]

Old developing agents usually work fine, even when they have started to discolor. The discoloration generally affects only a very small part of the chemical crystals. I have some phenidone which is quite ancient and rather yellow, but it still works as intended. Of course, there is a limit. I wouldn't trust really old, black stuff. You should test questionable chemicals on something unimportant.