What was/is Meritol?

Discussion in 'B&W: Film, Paper, Chemistry' started by Jerevan, Sep 11, 2006.

  1. Jerevan

    Jerevan Subscriber

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    I was looking in a photographic book today, and found some chemistry recipes, one of which included Meritol. The book was reprinted in 1947, just to give a clue to its age.

    I did a google on that name and came up with hexahydric alcohol, chemical name C6H14O6 and CAS 50-70-4. It seems more commonly known as Sorbitol.

    Could it be this (sounds strange) or was Meritol a proprietary chemical substance?
     
  2. Nick Zentena

    Nick Zentena Member

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    The formula in my book is:

    C6H4(OH)2: C6H4(NH2)2 =218

    Patented by Johnson and Sons LTD. No date given.

    Fine grain developer
     
  3. Seele

    Seele Member

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    According to The Focal Encyclopaedia of Photography, Meritol has the formula of C6H4(OH)2.C6H4(NH2)2, molecular weight 218.

    Meritol was a proprietary developing agent made by Johnsons.
     
  4. Jerevan

    Jerevan Subscriber

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    Thank you very much,

    judging from that formula, it seems to be composed of catechol and possibly o-phenylenediamine. But I am no chemist, as you already have understood by now, just curious by nature. :smile:

    The formula consists of Metol, Meritol, Sodium Sulphite and water. And in the book it's called Johnsons Meritol-Metol, for obvoius reasons...
     
  5. Helen B

    Helen B Member

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    I mentioned it in the recipe for MCM100 in the recipes section here:

    "Meritol was a proprietary Johnson developing agent, a compound of p-Phenylenediamine (PPD) and catechol. The 16 g of Meritol can be replaced with 7 g of PPD and 9 g of catechol."

    The book wouldn't happen to be Jacobson's Developing would it?

    Best,
    Helen
     
  6. Jordan

    Jordan Member

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    One of the problems with organic chemistry is that the structural formulas often don't mean much. C6H4(OH)2 could conceivably represent either hydroquinone, catechol (both photochemically active) or resorcinol (not photochemically active), the three isomers of dihydroxybenzene. Similarly, there are a few isomers of phenylenediamine that could be represented by C6H4(NH2)2.

    Since it's used photographically, my guess is that Meritol is probably some kind of co-crystal of para-phenylenediamine with either hydroquinone or catechol.
     
  7. Jordan

    Jordan Member

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    I simulposted with Helen, I guess. Still, it's nice to know I was on the right track.
     
  8. Jerevan

    Jerevan Subscriber

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    Thanks for the clarifications - now I know what I am looking at... wasn't sure if it was o-, m- or p-phenylenediamine.

    No, the book is actually "Photography by Artificial Light" by Marcel Natkin who also wrote the book "Photography without Tears". :D

    I might as well give the whole of the recipe and it is as follows, verbatim apart from the left out avoirdupois quantities:

    Metol - 2.3 grammes
    Meritol - 13.7 grammes
    Sodium Sulphite (crystals) 90 grammes
    or
    Sodium Sulphite (anhydrous) 45 grammes
    Water up to - 1 litre

    Dissolve the chemicals in the order given.
    Develop for about 12 minutes at 65 F or 18 C for fast films.
    1 litre will develop from 8 to 10, 36 exp. 35 mm. films.


    What constituted fast films in 1947 is probably something like ISO 160-200 today, I suppose. According to the text, extremely fine grain is obtainable with this formula.
     
  9. piticu

    piticu Member

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    Do you mind digging the book out and check the page no that formula is on? Or scan the page if it's not too much to ask?
    I need that info for a small project i'm working on. http://bwformula.atelierelealbe.eu/index.php/JJ97
    Thanks
     
  10. Ian Grant

    Ian Grant Subscriber

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    Here's the complete list of Meritol formulae that Johnsons published

    MCM100 was devised by a column writer for Miniature Camera Magazine just before WWII, apart from being a keen photographer and writer he was also the advertising agent for both Ilford & Johnsons so had strong ties with the photographic industry.

    Johnsons is the oldest of all photographic companies still trading (as Johnsons Photopia), they supplied Silver Nitrate ect to Fox Talbot, although they closed their chemistry division in the early 1970's.

    Ian
     
  11. Alan Johnson

    Alan Johnson Subscriber

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    From "Amateur Photographer" Sept 25 1946:
    "The sustance known as Meritol consists of a compound or mixture in equimolar parts of para-phenylenediamine and pyrocatechin.
    The preparation is carried out as follows according to Patent Specification No.466,626 of Jun 1st, 1937:-
    100 lb para-phenylenediamine is dissolved in 80 gallons of a 10 per cent solution of sodium bisulphite with the aid of heat, 2 lb decolourising carbon added, the mixture well stirred for 10 minutes and filtered hot; to this a hot solution of 100 lb of pyrocatechin in 20 gallons of a 10 percent solution of potassium metabisulphite is added; on cooling the new compound separates out in beautiful colourless prismatic crystals which melt at 110 degrees C and are remarkably stable in the air.
    Similarly by substituting an equivalent quantity of pyrogallol or chlorquinol for the pyrocatechin in the above example the corresponding compounds are readily obtained."

    I mention this out of interest only,NB some of these substances are highly toxic, don't try this at home!
     
  12. Philippe Grunchec

    Philippe Grunchec Member

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  13. Gerald C Koch

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    Meritol was the tradename for the addition product of p-phenylenediamine and catechol. Once dissolved it dissociated into its two components. Nothing magical and not really a useful developing agent with today's emulsions.
     
  14. Ian Grant

    Ian Grant Subscriber

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    I think your maybe wrong Jerry. I use Meritol based developer as a teenager and i think that a PPD-Pyrocatechin developer like Pyrocat would have great potential. I don't think I'd use 50/50 ny MW though, much less PPD so strictly it would be Meritol-Pyrocatechin.

    Ian
     
  15. Gerald C Koch

    Gerald C Koch Member

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    Hi Ian,

    Such developing agents as Meritol were a response to the thick emulsions of the time. They did provide finer grain but at the expense of sharpness and speed. Many years ago I got caught up with the search for the "holy grail" of developers. I tried several PPD developers and also solvent types such as Microdol. All yielded finer grain but with mushy images. With today's finer grain films, I see no advantage in their use. Of all the developing agents ascorbic acid seems to be closest to the ideal. Ascorbic acid produces much less infectious development than any other developing agent thereby yielding greater sharpness.
     
  16. Ian Grant

    Ian Grant Subscriber

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    Unfortunately Johnson's later proprietary developer formulae have never been published. The company was poorly managed and they dropped their raw photochemical manufacturing side and then their chemistry. Their chief chemist Pip Pippard set up Photo Technology with others but they mainly specialised in Colour chemistry and made a only a small B&W range.

    Johnson's had fine grain developers with excellent definition, but the key isn't Meritol, it's PPD for the fine grain and Pyrocatechin for the definition.

    You could reformulate Pyrocat HD with PPD instead of Phenidone, it'd be slower but probably finer grained. I think the mistake is to think that Johnson's Meritol is a "New" developing agent, which is what they claimed. Edmund Lowe thought differently :D

    Ian
     
  17. Jerevan

    Jerevan Subscriber

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    Of course I can do that, if you still are interested. Sorry about the late reply but life (relationship breakup, new home, no darkroom, etc, etc) has come between me and APUG for the last 7-8 months.
     
  18. Jerevan

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    Let's see if the uploaded picture is enough to read the text from the book - it's not much, just the recipe and that's it.
     

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  19. K-G

    K-G Subscriber

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    Good to see you back again.

    Karl-Gustaf
     
  20. Jerevan

    Jerevan Subscriber

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    Thanks Karl-Gustaf!

    Well, I guess things are coming along in the right direction again. The analogue, darkroom direction that is. :smile:
     
  21. nworth

    nworth Subscriber

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    My references show it as a combination of one mole catechol with one mole p-phenylenediamine. The dry product was probably the adduct, but you could also probably just substitute the proper amounts of the constituents.