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  1. #1
    Ian Grant's Avatar
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    Modern Rodinal Substitutes Part II

    Apologies for having to start a new thread but I can't read or even access the first to reply to posts.

    So with a bit of telepathy

    Quote Originally Posted by Kirk Keyes View Post
    Well, there's a problem there, as it's really hard to measure pH accurately when it gets much above 12.5 or so. You have to start getting special electrodes and the like.

    But for MSDS work, it doesn't have to be too precise.
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    Kirk

    A point that's being missed is that A&O give a figure of 2.7% Potassium Hydroxide not 3% in older Agfa MSDS.

    The pH is around 14 sure, but the actual requirement is the pH of the working dilute solution rather than the concentrate which is given elsewhere as pH 11.55, which I commented on in the first post of the thread.

    Way back Ron (PE) mentioned adjustments to Rodinal before bottling, the question we need to ask is are they adjusting on the basis of the concentrate, or also doing some tests on a dilute sample, as this will be a far more accurate indicator.

    Can someone please post a link to this continuation on the original post.

    Ian

  2. #181
    gainer's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    You can use your pH meter too if you like. Just titrate to pH 7. I was trying to keep it simple by mentioning an indicator. But nowadays, most tinkerers will have a pH meter.
    I took your suggestion. I made some KOH using the K2CO3 and CA(OH)2. A 0.1 normal solution of ascorbic acid added slowly to a sample diluted 10:1 gave a pretty sharply defined transition form basic to acidic on my pH meter. I estimated closely enough for government work that the KOH I made was about 1.25 N.
    Gadget Gainer

  3. #182

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    Actually, you don't even need to make the ascorbic (or KHP) to a particular normality. You can simply weigh a known amount into a beaker and add enough water to get the solution high enough for your pH electrode (or add your indicator), and then start titrating. It's kind of funny, as KHP does not even typically disolve into solution before the start of the titration. It will dissolve a bit, and then as the titration goes, the dissolved portion reacts with the KOH (or whatever basic solution you are titrating) and some more KHP will dissolve. As you are getting near the endpoint of the titration, all the KHP will go into solution.

    So the important thing when doing this is to know how much KHP (or ascorbic) you wieghed out so you can do the calculation to determine the normality of the base. So typically, when standardizing bases, one puts the standard acid in the beaker, and then titrate with the base. But it works the other way too.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  4. #183

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    Quote Originally Posted by gainer View Post
    Some years ago, I used HC-110 a lot, even for developing paper. For film, I usually added a modicum of ascorbate. For paper, I added some carbonate and some sulfite, IIRC. It was always reliable and quick to prepair, which was a virtue at the time. I was working for NASA, principal oboist for both Peninsule and Norfolk Symphonies, and photographing guest artists at dress rehearsals, providing them with prints the next day. Did I mention having six kids?

    I have a portion of a bottle a couple of years old, looks and works like new.
    And what on earth did you do with all your spare time??

    Bob H
    "Why is there always a better way?"

  5. #184
    gainer's Avatar
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    Quote Originally Posted by BobNewYork View Post
    And what on earth did you do with all your spare time??

    Bob H
    That's when my wife and I worked on making the kids. It was a lot of fun, too.
    Gadget Gainer

  6. #185
    gainer's Avatar
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    Quote Originally Posted by Kirk Keyes View Post
    Actually, you don't even need to make the ascorbic (or KHP) to a particular normality. You can simply weigh a known amount into a beaker and add enough water to get the solution high enough for your pH electrode (or add your indicator), and then start titrating.
    That in fact was what I did. I figured it would take a mole of KOH to neutralize each mole of ascorbic acid I put in. The swing from <7 to >7 in pH was abrupt enough to satisfy this need, even if my pH meter had been somewhat out of adjustment. I didn't find out tll later that the solubility of KOH is less than 2 MW/liter. DUH!
    Gadget Gainer

  7. #186
    gainer's Avatar
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    I didn't use a full MW of ascorbic acid. Just the mole fraction, w/176.
    Gadget Gainer

  8. #187
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    I would like to point out that the Normality may be more important than Molarity when it comes to Ascorbic Acid.

    PE

  9. #188
    gainer's Avatar
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    One thing we know. If you have p-aminophenol and a strong alkali like KOH or K2CO3, you can develop film. Of course, without sulfite it will be grainy and lack film speed. Or will it? I tried this combination with 500 ml water, 1.5 grams p-aminophenol base, and enough of Sandy King's 75% K2CO3 part 2 to dissolve the p-ap. 8 minutes, 68 F, EDU 400 Ultra. The result is attached.

    You will not see anything in this very rough test that you would not see in a Rodinal test using the same scene. What happened to the grain and all the other problems you might have expected from such an unadorned developer solution? Surely, you wouldn't expect to be able to make a long lived concentrated stock solution with just these two ingredients, but there are other ways to preserve solutions of p-aminophenol. One is to dissolve it in glycerine or in propylene glycol, and keep a bottle of Sandy's B solution handy.

    I know for fact that at least 36 grams of p-aminophenol are soluble in a liter of either glycerine or propylene glycol. I have used either KOH or the carbonate with both of them, addig sulfite or not to the working solution. If I keep the sulfite to the proportions you would get by putting the suggested 384 grams in the stock, you would have only 7.7 grams in a liter of working solution. Seems hardly worth the trouble if you don't need it as a preservative for the stock.

    You can get a handy little 4 fl. oz. bottle of very pure glycerine at most pharmacies to play with. 9 or 10 grams of p-aminophenol will go into that with a little persuasion in the form of heating and stirring.

    How much Pyrocat "B"? Some must go into forming the potassium aminophenolate, and some more into raising the pH to a decent working speed. My rough test used 5 ml when I diluted 10 ml of the p-aminophenol solution with 50 parts of water.
    Attached Thumbnails Attached Thumbnails PAPCARB 25 ALL.jpg   papcarb 25.jpg  
    Gadget Gainer

  10. #189
    gainer's Avatar
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    The direct scan of the negative showed meither the true resolution of the detail nor the grain. I made a 10X enlargement in the darkroom and scanned the attached detail view from it.

    I measured base+fog of the negative at 0.24, the darkest point of the scene at .28, and the scene highlight at 1.3. This range is a little large for grade 2 so I made the print on Arista VC with 30 Y filtration.
    Attached Thumbnails Attached Thumbnails PAPCARB HIRES.jpg  
    Gadget Gainer

  11. #190
    gainer's Avatar
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    With regard to film speed: I set my camera for 400, the box speed, and to bracket plus & minus 1/2 stop. What I have shown here is from the box speed.
    Gadget Gainer



 

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