HCA test?

Discussion in 'Darkroom Developing and Printing' started by Tom Phillips, Sep 29, 2004.

  1. Tom Phillips

    Tom Phillips Guest

    Greetings everyone:

    So, I'm back in my darkroom after a long summer and decided
    to use up some old chems. Things are generally long-lived in
    my basememt and I've got some 5 gal. packages of KHCA. These
    are old -- possibly 5 - 10 years.

    The general 'is it good v. bad' is the color of the powder,
    though I've never actually seen sulfite turn brown. The oldest
    looking package was still a sugar white. Some have said if it
    has a sulfur dioxide smell it's bad Anyway no smell and mixed
    to a clear liquid.

    I've got a lot of this stuff and I could do some HT-2 tests (fix,
    hypoclear, short wash, test for fixer residue) to assess the
    efficaciousness of the old hypoclear+wash but was wondering
    (richard or anyone else...) is there any chemically viable
    known method to test the HCA solution directly.

    TIA Tom Phillips
    Tom Phillips, Sep 29, 2004
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  2. Tom Phillips

    Dan Quinn Guest

    Problem is it's Kodak HCA. There is no knowing precisely
    it's composition at start.
    You could compare the old with some new using permanganate.
    You will have some idea of how much it has oxidized. Dan
    Dan Quinn, Sep 30, 2004
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  3. KHCA contains a lot of sodium sulphite, some sodium metabisulphite, and
    perhaps a sequesterant.

    The simplest solution (no pun intended) is to use the stuff one-shot, or
    nearly one-shot. When processing film, I use it one-shot. When processing
    paper (and I do it manually in trays), I dump it when I am done or in 4
    hours, whichever happens first.

    This may be wasteful, but I need not worry about exhausting it at the rate
    I make prints.
    Jean-David Beyer, Sep 30, 2004
  4. The principal ingredient in KHCA is Sodium sulfite. When
    it is oxidezed sulfite become sulfate. Sodium sulfate does
    no harm but is not nearly as effective as a wash aid as is
    sulfite. The chemical does not change color when oxidized.
    The brown in developers is an oxidation product of either
    the Metol or Hydroquinone, since wash aid contains neither
    it does not turn color.
    I am not a chemist so I don't know what the test is for
    sulfite nor if the presence of the metabisulfite, the other
    key ingredient, would affect it. Probably the easiest test
    is a wash test. Film should wash out in about five minutes
    when treated in KHCA and in about 30 minutes when not
    treated (hardening fixer). A sulfide test will tell if the
    KHCA is working. The stuff does not have a long life when
    mixed but unless the Kodak bags are damaged it should have a
    shelf life of at least two years.
    I agree about the Sulfur dioxide odor, it would indicate
    decomposition of the sulfite but not oxidation, so it could
    be odor free and still not effective.
    Sorry I can't do better but perhaps there is a genuine
    chemist following this group who can give a method of
    analysing the stuff.
    Richard Knoppow, Sep 30, 2004
  5. I believe NaSO3 -> NaSO4 only takes place in the presence of
    water. If the powder is dry then it should be OK.

    The pH of a sulfite solution should drop as it oxidizes to
    sulfate. I do not know what the pH values would be.
    pH paper may be sensitive enough to pick up the change.
    Nicholas O. Lindan, Sep 30, 2004
  6. Tom Phillips

    Tom Phillips Guest

    Don't have permanganate, however. Unfortunately I chose not to get
    it with a recent order at formulary...
    I never keep HCA past a single session, and I believe Kodak states
    no longer than 24 hours. The capacity is enormous: about 14000
    square inches per working gallon.
    Tom Phillips, Sep 30, 2004
  7. Tom Phillips

    Tom Phillips Guest

    Richard -- do you mean an HT-2 test? The only formula I have
    for a sulfide test is ST-1 for testing for adequate fixing.
    Tom Phillips, Sep 30, 2004
  8. Tom Phillips

    Tom Phillips Guest

    Are you saying the powdered form does not then oxidize?
    Tom Phillips, Sep 30, 2004
  9. Tom Phillips

    Dan Quinn Guest

    To order from the Formulary you'll need to some paper work.
    Permanganate is a restricted substance. The least little bit
    of it will go a long way.
    I've played with it a bit. It can be used to test wash water
    for minute amounts of hypo. Dan
    Dan Quinn, Oct 1, 2004
  10. Tom Phillips

    Tom Phillips Guest

    Since you're the only one who has suggested it, Dan, could
    please explain the proceedure.

    The paper work was the reason I elected to not order it.
    Could have but it added 20 minutes labor to a phone order...
    Tom Phillips, Oct 1, 2004
  11. Tom Phillips

    Dan Quinn Guest

    For now I'll point you to a thread posted some years ago.
    Search rec.photo for, residual fixer tests . Two of the few
    methods mentioned use permanganate.
    Also the Kodak Hypo Test Solution HT-1a is a wash water
    test. I've not been able to relocate it via Google. I've a
    print out. It may be in some old text.
    I've one other source of information but will need to
    dig it up. Dan
    Dan Quinn, Oct 2, 2004
  12. If that is the old permanganate test for hypo, it is fairly worthless. It
    is not a test of KHCA, though. I have tried it, and it never revealed
    excess hypo in prints unless I tested them right out of the hypo bath 2.
    After washing for a few minutes, even poorly washed prints passed the
    test. I had no trouble getting a 4 ounce bottle of KMnO4 from B&A, a
    subsidiary of Allied Chemical. But that was in the 1970s. I still have
    most of it left.
    Jean-David Beyer, Oct 2, 2004
  13. Tom Phillips

    Dan Quinn Guest

    Are you speaking of the Kodak HT-1a test? That test does
    differ some from other tests.
    Permanganate can be used to test sulfite. I think it should be
    usefull in gageing the exhaustion of HCA solutions.
    I've nearly completed a redue of my darkroom and will soon
    see how it does. Dan
    Dan Quinn, Oct 3, 2004
  14. Your are correct, I meant the silver nitrate test for completeness of washing.

    Richard Knoppow
    Los Angeles, CA, USA
    Richard Knoppow, Oct 3, 2004
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