Differences in Phenidone and Dimezone?

Keith Tapscott. · Sep 9, 2007

Out of curiosity, what are the differences, advantages and/or disadvantages of Dimezone over regular Phenidone? As an example, Ilford are using Dimezone-S in their liquid concentrated developers and Phenidone in their Microphen film developer and Bromophen paper developer.
Can one replace the other weight for weight, or is one better than the other in specific applications such as speed, sharpness, longevity etc?

http://www.silverprint.co.uk/PDF/paperdeveloper.pdf

Snapshot · Sep 9, 2007

I believe that Dimezone S has improved keeping properties over Phenidone, which is why it would be preferred by manufacturers.

Roger Hicks · Sep 9, 2007

Snapshot said:
I believe that Dimezone S has improved keeping properties over Phenidone, which is why it would be preferred by manufacturers.

Almost certainly hydrolysis resistance: as a powder, the developing agent is not subject to hydrolysis until it is mixed.

Kobin · Sep 9, 2007

Phenidone is more active; use 1.44 times more Dimezone-S for a quantity of phenidone if you home brew.

K.

Keith Tapscott. · Sep 9, 2007

Roger Hicks said:
Almost certainly hydrolysis resistance: as a powder, the developing agent is not subject to hydrolysis until it is mixed.

I have read somewhere about the problem of hydrolyses with Phenidone when it goes into solution, hence the reason for Dimezone-S in liquid concentrates. What I am trying to understand is, if Dimezone-S is more resistant, why isn`t it used in the dry powder developers as well?
Kobin mentions that using 1.44 times more Dimezone-S for the quantity of Phenidone provides equal activity, although I haven`t found where I can find this information. Is this due to the cost of packaging or for another reason? :confused:

craigclu · Sep 9, 2007

I've drifted away from some old, favorite Dimezone S based developers as my Dimezone seemed to go off for me. Is it quite unstable in dry form? I initially had very nice results with Ryuji's developers (film and paper) along with some of my own variants and then, it seemed that I wasn't getting predictable activity. The other components seemed to work as expected in other mixes but anything including my supply of Dimezone S seemed to lack the activity I was accustomed to with it. I also notice that the color went from a light straw to a more orange coloring. Does anyone have any track record with this? Is there a better way to store? Broken into smaller, fuller containers? As a solution?

Photo Engineer · Sep 9, 2007

There are Phenidone, Dimezone and Dimezone-S available as good developing agents. Phenidone does decompose in alkaline solution more readily than the other two.

Developers compounded properly with any one of the three will look pretty much the same but the Dimezone and Dimezone-S will last longer.

PE

Keith Tapscott. · Sep 9, 2007

craigclu said:
I've drifted away from some old, favorite Dimezone S based developers as my Dimezone seemed to go off for me. Is it quite unstable in dry form? I initially had very nice results with Ryuji's developers (film and paper) along with some of my own variants and then, it seemed that I wasn't getting predictable activity. The other components seemed to work as expected in other mixes but anything including my supply of Dimezone S seemed to lack the activity I was accustomed to with it. I also notice that the color went from a light straw to a more orange coloring. Does anyone have any track record with this? Is there a better way to store? Broken into smaller, fuller containers? As a solution?

Perhaps this is why that Ilford doesn`t use Dimezone-S in their dry powder developers, although I am not sure whether they are using Phenidone B (Dimezone) in place of Phenidone A with Microphen and Bromophen these days?

Roger Hicks · Sep 9, 2007

Keith Tapscott. said:
I have read somewhere about the problem of hydrolyses with Phenidone when it goes into solution, hence the reason for Dimezone-S in liquid concentrates. What I am trying to understand is, if Dimezone-S is more resistant, why isn`t it used in the dry powder developers as well?
Kobin mentions that using 1.44 times more Dimezone-S for the quantity of Phenidone provides equal activity, although I haven`t found where I can find this information. Is this due to the cost of packaging or for another reason? :confused:

Dear Keith,

For the former, it's simple time: the made-up solution will oxidize before the Phenidone hydrolyses, whereas a liquid concentrate will be in aqueous solution for months or even years longer.

For the latter, sorry, dunno. But I'd recommend biting the bullet and buying a copy of Haist. With the current hopelessly feeble dollar it's probably under a hundred quid including shipping.

Cheers,

Roger

Photo Engineer · Sep 9, 2007

Well, phenidone oxidizes and also ring opens with alkali. So, the chemists came up with dimethyl phenidone (dimezone) which was more stable to alkali, and then they came up with methyl, hydroxy methyl phenidone which was even more stable. In fact, the latter two are so stable they can be used in concentrated alkali such as in instant product pods.

The activity ratio of phenidone to dimezone depends on the other auxiliary developer and its concentration as well as pH. You see, since dimezone can stand a more alkaline environment, you can raise the pH to gain activity, but you cannot do that with phenidone or you risk decomposition.

As Roger says, phenidone does not decompose all that rapidly or concentrates of phenidone developers could not be made and have a reasonable shelf life. So, alkaline stability is not a huge problem, just enough of one to lead to the development of the other two. It gives more flexibility to the designer. (the latter two also avoided patent issues which is another plus)

PE

Kobin · Sep 9, 2007

Keith Tapscott. said:
Kobin mentions that using 1.44 times more Dimezone-S for the quantity of Phenidone provides equal activity, although I haven`t found where I can find this information. Is this due to the cost of packaging or for another reason? :confused:

I think I got this from Ryuji's Silvergrain site, but I can't remember for certain. I have the Dimezone S equivalents written next to the phenidone quantities on my formulae, and the difference is 1.44 times, so I must have gotten it from somewhere. Maybe somewhere on Unblinking Eye if not Silvergrain.

K.

Photo Engineer · Sep 9, 2007

Kobin said:
I think I got this from Ryuji's Silvergrain site, but I can't remember for certain. I have the Dimezone S equivalents written next to the phenidone quantities on my formulae, and the difference is 1.44 times, so I must have gotten it from somewhere. Maybe somewhere on Unblinking Eye if not Silvergrain.

K.

This is not a hard and fast rule!

It is dependant on a lot of factors as I noted in a previous post.

PE

Cor · Sep 10, 2007

Kobin said:
I think I got this from Ryuji's Silvergrain site, but I can't remember for certain. I have the Dimezone S equivalents written next to the phenidone quantities on my formulae, and the difference is 1.44 times, so I must have gotten it from somewhere. Maybe somewhere on Unblinking Eye if not Silvergrain.

K.

I am too lazy to exactly calculate it, but AFAIK is the difference caused by the higher molecular weight of Dimezone-S versus Phenidone; that is I would not be surprised if Mw Dimizone-S/ Mw Phenidone is around 1.44.

But again as PE already mentioned : it depends....but I guess it cannot harm to apply this rule as a starting point.

Ps I too noticed a colour shift in my Dimezone-S stock (powder), but I did not observe an activity drop. But I only use it for my paper developer (DS-14).

best,

Cor

billtroop · Sep 10, 2007

Where does this 1.44 figure come from? I was told by D. Dickerson and S. Zawadski at Kodak that the differences between amounts required of phenidone and Dimezone-S were not substantial in their experience. 1.44 is a lot, and might reflect personal experience with different batches of phen/dim-s of varying strength. When both are perfectly fresh, I don't think the differences are great. As neither seem particularly stable in powder form, perhaps a nitrogen blanket would help?

john_s · Sep 10, 2007

If the molecular weight were the sole reason for differing amounts of Dimezone-S to be used instead of phenidone the factor would be x1.27.

Sandy King found that the activity of pyrocat-HD didn't vary within a range of phenidone levels, so maybe it doesn't matter. I have used about x1.4 as my factor for using Dimezone-HD based on Sandy's saying that a bit more phenidone didn't hurt. (i.e 1.4=1.27plus a bit more)

Kobin · Sep 10, 2007

Well, crap! Can't find any source for the 1.44 figure in my notes, although I have found the 1.27 figure. I guess too much aromatic hydrocarbons in the darkroom cause hallucinations. Fortunately for me, the mixes work well even with the spurious fudge factor. I'll try using 1 for 1 and save a little chemistry. Please forget I even posted in this thread.

K.

craigclu · Sep 10, 2007

Kobin said:
Well, crap! Can't find any source for the 1.44 figure in my notes, although I have found the 1.27 figure. I guess too much aromatic hydrocarbons in the darkroom cause hallucinations. Fortunately for me, the mixes work well even with the spurious fudge factor. I'll try using 1 for 1 and save a little chemistry. Please forget I even posted in this thread.

K.

I, too have the 1.44 written in my notes and also recall the 1.27 molecular weight comparison. I also share your lack of a source! It must have seemed credible or I wouldn't have made the notation but I can't recall now.... I quit substituting it when I noted a lack of comparable activity and shifted to PG and TEA based variants that didn't gain from the stability difference said to be available in water. It also seemed harder to get suspended in PG and TEA than phenidone anyway. Now I'm starting to wonder if my batch had started to go off at that time already.

Photo Engineer · Sep 10, 2007

Well, our formula at Kodak was to use what worked. I don't remember any 'factor' as it was different in every case. I think Bill Troop's comment reflects my experience.

PE

Keith Tapscott. · Sep 12, 2007

I looked in the book, `Modern Photographic Processing`(Volume 1) by Grant Haist (page 184) as suggested by Roger and found Phenidone (1-Phenyl-3-Pyrazolidone), the 4-methyl derivative called Phenidone B or sometimes Methyl Phenidone and Dimezone (dimethyl Phenidone). It mentions that the latter two are more stable than Phenidone in concentrated liquid developing compositions that may be maintained at high temperatures or may be stored for long periods of time.
I didn`t find any references to the stability or longevity of either of these when kept in dry powder form, although I acknowledge that other factors such as the way these are packaged and stored will play an important role.

Photo Engineer · Sep 18, 2007

Dimezone S = Methyl, Hydroxymethyl Phenidone. This was the latest and last derivative I worked with. Each had increasingly better properties. So, basically there are 4 'phenidones' that we must be aware of. Each individual derivative here must be adjusted for its own properties in a given developer depending on co-developers and pH as well as other ingredients.

PE

Differences in Phenidone and Dimezone?

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