Metol+Phenidon .... superadditive?!

Discussion in 'B&W: Film, Paper, Chemistry' started by Relayer, Sep 14, 2011.

  1. Relayer

    Relayer Member

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    Well known that metol isn't superadditive with phenidon. But I found patent US 5998110. Author research some types developer (PQ, PC, PM(etol), PG(lycin)) at pH ~10 and claim that PM combination is superadditive and have same speed as PQ/PC with near same ratio of phenidone to 2nd developer agent

    Also in this patent found interesting research of changing pH of developer during oxidation (see example 3, table 4). Initial pH of all tested developer is same - 10.27. For 72 hours of oxidation PQ change pH to 12.27, PC - to 8.82 and PM to 11.5
     
  2. Ian Grant

    Ian Grant Subscriber

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    Ilford did publish a Metol/Phenidone/Hydroquinone developer in s Patent and Crawley mixed all 3 but I've never seen any benefits of using both Metol & Phenidone.

    Ian
     
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  3. Relayer

    Relayer Member

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  4. Alan Johnson

    Alan Johnson Subscriber

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    Crawley,BJP Dec16 1960 explained why metol-phenidone-hydroquinone gives more speed than phenidone-hydroquinone:

    "In FX-4 the metol-phenidone-hydroquinone combination is used.This reduces overall contrast and allows the shadows to increase in contrast more than (phenidone-hydroquinone) FX-3 by the time normal gammas are reached...."

    I wonder if speed increase may sometimes incorrectly be attributed to superadditivity when it is in fact due to the mechanism Crawley describes.

    The same question arises in respect of your attributing properties of phenidone -glycin to superadditivity in your metol glycin developer thread.Crawley's simple explanation may suffice.
     
  5. Relayer

    Relayer Member

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    pls read patent before reply )) we talk about developer with two component. not 3, 4, 5, or many ))
    about glycin:
    also additivity of phenidon+glycin found in Anchell "Cookbook"
     
  6. Relayer

    Relayer Member

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    also superadditivity phenid+glycin described in patent US3778267 - modified POTA developer with glycin
     
  7. ntenny

    ntenny Member

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    Well, a patent doesn't have to be technically correct to be issued, exactly. It is supposed to be "operable", but patent offices do not ordinarily enforce a "must prove operability" requirement. The history of patents for perpetual-motion machines is interesting in this regard (and eventually led the USPTO to establish a specific prohibition on patents for that particular impossibility, since they were so numerous as to be a nuisance to the office).

    On the other hand, the inventor was apparently employed by Ferrania and involved in multiple other developer patents, so I'd expect the filing not to be complete nonsense. (On the third hand, I've filed some applications for things that might lead a reader with the benefit of hindsight to say "What the @#(*&@ was this idiot thinking?")

    Claims 2 and 4 do seem unambiguously to imply that the inventor thinks metol and phenidone are superadditive. I guess either the inventor is wrong, or everyone else is?

    Finally, it really worries me that the only patent with a reference to this one is a "Boar cart for insemination of sows"!

    -NT
     
  8. kreeger

    kreeger Subscriber

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    I have a photographic science background and worked with these two compounds extensively on some special mil spec developers back in the 1980s. We had some very interesting formulas for special one-off Kodak SO (special order) type films that ran about $600 for 15gallons because each batch was hand weighed out back in Rochester and nobody knew exactly what was in it but came in special. It oxidized in one week and we threw it out!!

    Ilford invented Phenidone.

    Phenidone is generally accepted as a synthetic substitute for Metol and can be interchanged as long as you know the formula. If memory serves me right Phenidone was about 10x the power of metol, so 10 grams of Metol = 1 gram of Phenidone.

    It's also hypoallergenic compared to Metol so if you get a reaction to Metol based developers try Phenidone variants. Developers with Phenidone in them have a very sweet smell and have a pink tint to them initially.

    I cant comprehend what you would gain by using both that you couldn't accomplish with just using more Phenidone or a lot more Metol in the formula. The result is the low contrast range of course, and you could use a variety techniques to accomplish that.
     
  9. phfitz

    phfitz Member

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    (sorry for the hi-jack, could not help it)

    "The history of patents for perpetual-motion machines is interesting in this regard (and eventually led the USPTO to establish a specific prohibition on patents for that particular impossibility, since they were so numerous as to be a nuisance to the office)."

    a perpetual-motion machine produces more power than it consumes!
    under that definition at least 2 have been patented and produced and released to the general public

    1) Tesla's bladeless turbine (1914?) by itself it's a marvel but when a second unit is attached to and driven by the first it acts as a 'super-charger' producing much more power than it consumes.
    2) Ford's ceramic catalytic converter, the orginal 'cat' was patented in the 1950's, Ford made it easier to produce in the 1970's. It produces quite a lot of energy (power) and consumes almost nothing but fresh air.

    Combine the two and watch what happens.
     
  10. Relayer

    Relayer Member

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    may be we back to photo? )) from patent US5998110:
    at pH 10.7:
    2.25g/l phenidon + 20g/l hydroquinone reach Dmax 3.45
    2.25g/l phenidon + 30g/l metol reach same Dmax 3.45
    30g/l metol without phenidon have Dmax less than 1
    author can't test developer with only phenidon, but as well known phenidon as single deveping agent produce very low gamma and Dmax (see POTA and modification)
    so if phenidon+metol isn't superadditive Dmax(phenidon+metol)=Dmax(metol)+Dmax(phenidon) < 2, but we have Dmax(phenidon+metol)=3.45!
    I think that this result need more arguments for refute than like "this is bull$%^#" or "perpetual motion"
     
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  11. Alan Johnson

    Alan Johnson Subscriber

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    I agree you are right about superadditivity of phenidone glycin described in this thread:
    http://www.apug.org/forums/forum37/96046-metol-glycin-two-bath-experiment.html
    Mason p29 does say phenidone glycin is superadditive but does not say it is of poor utility.
    I found glycin pyrocatechol is superadditive. In Pyrocat HD 2g/L phenidone can be replaced by 10g/L glycin (25 g/L precipitates out after a month or so).

    Regarding US Patent 5998110,results in table 1 and table 2 suggest metol alone does not work, metol + Dimezone S does.,results in table 5 that Dimezone S with very little metol does not work very well.They seem to conclude superadditivity of metol Dimezone S when developing X-ray film 20seconds 35 degrees C.

    I think it is speculation to conclude superadditivity at normal temperature 20C when developing ordinary pictorial film.
     
  12. Relayer

    Relayer Member

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    have you any information about temp treshold for superadditivity effect?
     
  13. ntenny

    ntenny Member

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    But superadditivity is normally a function of the side products from one developer causing regeneration in the other, right? I'm no chemist, but in my understanding the reason that metol and the phenidone "family" aren't thought to be superadditive is that neither one can produce anything that regenerates the other. Why would that depend on temperature, or on the difference in emulsions between x-ray and pictorial films?

    By the way, my point with perpetual motion machines was just that "it's in a patent" is not by itself a strong indication of something being correct. Let's not automatically write off the possibility that the results in this case were just wrong---though again, based on the inventor's credentials, I think it's more likely that there's something going on here that we don't understand.

    -NT
     
  14. Relayer

    Relayer Member

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    my understanding of superadditivity two agent A and B is that D(A+B) strong great than D(A)+D(B). here D(x) - density obtained by agent x. I think that x-ray emulsion isn't very different from generic BW emulsion.
     
  15. Gerald C Koch

    Gerald C Koch Member

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    This isn't really true. If you read Mason, he speaks of velocity and not density. It is a matter of kinetics. Any increase in density is caused by the increase in activity. As a chemistry instructor of mine was fond of saying, "It is not the trees shaking that makes the wind blow but the wind that makes the trees shake."
     
  16. Alan Johnson

    Alan Johnson Subscriber

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    In "The Theory of the Photographic Process" by Mees and James is a section on superadditivity but I did not find any mention of temperature effects.However, James found ".. if an oxidation product of the first developing agent inhibits development,regeneration may effectively remove this this inhibiting product from the grain by converting it to active developer".

    It is quite well known that the oxidation product of phenidone (Also Dimezone S?) is of this type.So the question can be put if metol will regenerate this oxidation product and if the regeneration reaction depends on temperature.
     
  17. Relayer

    Relayer Member

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    Gerald, you right - velocity. but in same condition (pH, time, exp) as result of velocity we have density (I omit some mathematical background)
     
  18. ntenny

    ntenny Member

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    It seems to me that there are at least three "flavors" in which the combination of developers could be measured: "velocity" or rate of reaching a certain density (or CI?), Dmax, and (D-fog)max, which I guess is basically CImax.

    My impression is that what's normally considered is velocity: how long does the combination of developers take to get the negatives to a "done" condition? To some extent that should correlate with CImax, because the longer it takes to "finish" your highlights, the more time the developer has to build fog. But it's not clear to me that the two should necessarily be interchangeable.

    Dmax by itself doesn't seem like a very useful measurement: you can develop to completion with any developer, I suppose, though you might get so much fog that the image is useless.

    I'm completely talking through my hat here, though, and I'm late for a meeting.

    -NT
     
  19. michael_r

    michael_r Subscriber

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    I'm no chemist, but isn't there sometimes more to combining developing agents than superadditive behaviour?

    Also, while Phenidone is often described as a substitute for Metol, they don't work the same way in all respects, do they? For example, isn't Phenidone inherently more prone to streaking and uneven development than Metol? This can be a significant problem with POTA-type Phenidone developers, which I've observed myself. I remember reading (I think) about Glycin being combined with Phenidone in low contrast POTA-type developers mostly to improve uniformity.
     
  20. Ian Grant

    Ian Grant Subscriber

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    Never heard of Phenidone being more prone to streaking before.

    Ian