Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,212   Posts: 1,532,038   Online: 1182
      
Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15
  1. #11
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    I have located a source of Ammonium Ferric EDTA powder here: http://www.newalliance.biz/prange.swf

    It is made to customer order/specification, and the data sheet says it is 85% pure (max?).

    So, this may change the landscape a bit regarding powder blixes. I have to do some calulations. It may turn out to be uneconomical or it may turn out that due to purity there is an issue. This does not change the picture regarding blixing of films, just the potential activity of powdered blixes and bleaches that use Ammonium Ferric EDTA.

    I did this while Ian was sleeping in Turkey.

    PE

  2. #12
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    16,228
    Images
    148
    Photographers Formulary sell it, my old supplier (Rayco UK) sold it, I'd guess it's quite easy to source if you had a need for it.

    Ian

  3. #13
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Ian;

    The Formulary does not sell Ammonium Ferric EDTA in powder form. It is sold as the customary dilute solution prepared from Ferric Oxide, Ammonia and EDTA in special reactor to yield the dilute red solution we are familiar with. Working with this solution, you are limited in strength as to the Blix or Bleach you can prepare.

    PE

  4. #14
    Ian Grant's Avatar
    Join Date
    Aug 2004
    Location
    West Midlands, UK, and Turkey
    Shooter
    Multi Format
    Posts
    16,228
    Images
    148
    Ron, sorry I hadn't checked the Formulary's website I'd made a note that it was an alternative source since Rayco closed up. I wonder if it's a difference in manufacture between US/Europe a bit like Sodium Bisulphite & Sodium Metabisulphite, or perhaps it's just availability.

    I don't think there's many people left who make up their own colour chemistry any more so demands probably very low.

    Ian

  5. #15
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,972
    Images
    65
    Ian;

    There are several uses of Iron complexes with EDTA, but color photography is at the head of the list. Recently, with the introduction of NTA, the balance is shifting away from EDTA due to the higher BOD/COD of the latter and due to the "toxicity" of EDTA when in fact, EDTA is used intravenously in certain medical procedures (that being the secondary use of some of the complelxes).

    So, it is a rare beast just for color photography and it promises to get rarer and more expensive.

    Here is a scheme for making your own Ammonium Ferric EDTA. It should work. I have not made this in the lab for over 30 years though, so I'm writing this from old memory.

    Start with EDTA (the acid itself). Dissolve slowly in concentrated Ammonia solution (28%) until this is neutral and then add an equal molar (to the EDTA) quantity of Ferric Chloride. This will make a concentrate of Ammonium Ferric EDTA and Sodium Chloride in equal molar concentration. The pH should be about 6.5, never higher, and never lower than 4.0.

    If you go over about 6.5, you will precipitate Ferric Hydroxide which ruins the mixture and if you go below 4.0, the Ferric Ammonium EDTA will precipitate out. You will then have to make it alkaline and the dilution will decrease the strength of the concentrate.

    After you are done, add 1% excess of EDTA acid and readjust the pH. This last step is absolutely critical. If you omit it, you will cause severe stain in your photos. Iron salts will precipitate out in the film or paper and cannot!!!! be removed under normal circumstances.

    PE

Page 2 of 2 FirstFirst 12


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin