Kodalk, what is it/replacements

Discussion in 'B&W: Film, Paper, Chemistry' started by titrisol, Sep 23, 2004.

  1. titrisol

    titrisol Member

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    What is the composition of KODALK?
    Any ways to replace it?

    Is it borax/boric acid?
     
  2. ann

    ann Subscriber

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    Balanced Alkali. Which is also know as sodium metaborate. Anchell"s Darkroom Cookbook indicates the substitution can be weight for weight.


    Sodium Carbonate can be used as a substitute. However, it is not weight for weight.
     
  3. titrisol

    titrisol Member

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    Na-Metaborate (Na-BO2)
    That gave me better hits, like this one:

    Thanks ANN!!!
     
  4. Helen B

    Helen B Member

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    Here's Ryuji Suzuki's version of the story, and a bit more of a similar story from 20 Mule Team themselves.

    Best,
    Helen
     
    Last edited by a moderator: Sep 23, 2004
  5. titrisol

    titrisol Member

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    soo basically the formula i found would be a double concentration of kodalk?
     
  6. Helen B

    Helen B Member

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    I'm waiting to hear what others have to say. I recall reading a post by Patrick that gave similar proportions as RS, but it would be better coming from him than me.
     
  7. gainer

    gainer Subscriber

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    I suppose you are referring to this Patrick.

    Sodium metaborate 4 mol becomes sodium metaborate 8 mol at temperatures above about 53 C. Everything doubles, not just the water of crystallization. IOW, sodium metaborate 8 mol = 2(sodium metaborate 4 mol). This is according to the Arm & Hammer web site. Thus, if you start with the 4 mol at 20 C, you will have the same weight of the 8 mol at 60 C.

    The proper way to make the eqyivalent of 100 g of it it is with 69 g borax and 14.5 g lye. Borax is the official name for Na2B4O7.7(H2O), the stuff you get at the supermarket.
     
  8. ThomHarrop

    ThomHarrop Member

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    When we run out at school we use 20 Muleteam borax from the grocery store.
     
  9. dancqu

    dancqu Member

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    There are three oxygen acids of boron; ortho, meta, and tetra.
    IIRC, the formulas are in order; H3BO3, HBO2, and H2B4O7.
    You can see by the formulas that the acids are progressively
    dryer. That has to do with the temperature at which they are
    formed. At a high temperature all that's left is B2O3, the oxide.

    To 'hydrate' the sodium salt of the tetra acid, borax, sodium
    hydroxide is used. If you had tetraboric acid and wished the
    meta you would add hydrogen hydroxide, water.

    Lye is very hygroscopic. Excess of it will produce the ortho salt.
    I'd suggest having the metaborate on hand. Dan
     
  10. Deckled Edge

    Deckled Edge Member

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    Sodium metaborate, $16/kg at B&S. When I ran out of Kodalk, I ordered from B&S and it seems fine, though I have no way of differentiating heptahydrates from octahydrates. Results is results.
     
  11. gainer

    gainer Subscriber

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    Yes, you can replace it, and no, it is not borax+boric acid. I refer you to www.borax.com. Borax is the accepted common name for Na2B4O7.7H2O. Kodalk is either NaBO2.4H2O or Na2B2O4.8H2O, take your pick. They are equivalent. Above 53 C, NaBO2.4H2O becomes Na2B2O4.8H2O in solution. The mixture of borax and lye I gave above approximates that closely enough for government work.

    Just plain borax will not achieve pH = 10 no matter how much you dissolve.
     
  12. titrisol

    titrisol Member

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    OK, so is a buffered pH 10 alkali.
    Perfect, borax/NaOH is what I was looking for.
    Thanks guys!
     
  13. dancqu

    dancqu Member

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  14. gainer

    gainer Subscriber

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    Serves me right for not looking it up. Borax is the decahydrate. There is a heptahydrate of sodium carbonate, but it doesn't seem to have a common name. Its decahydrate is commonly known as washing soda. Maybe the fact that my brain's hard drive is 77 years old has something to do with it. This is the age when one may not only forget things, but also forget that he forgot them.
     
  15. gainer

    gainer Subscriber

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    "From my reading at www.borax.com both hydrates are stable.
    The 4 Mole has a little more ph per pound. Dan"

    The table I saw at www.borax.com showed a gradual change of pH with concentration and a transition from 4 mol to 8 mol above 53 C. I can't see how that jibes with what you saw. The molecular weight of the 8 mol is exactly twice that of the 4 mol, but a given weight of either one contains the same number of molecules. I don't think you can crystallize the 8 mol from a solution below 53 C. So far as I can see, the transition is reversible. I don't think there exists a solid NaBo2.8H2O.
     
  16. gainer

    gainer Subscriber

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    I should have said "a given weight of either compound contains the same number of atoms of Na, B, H and O."
     
  17. dancqu

    dancqu Member

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    At the borax site choose, products and services, then, our products.
    VIEW both the 4 and 8 mole technical info. Stability and solubility
    are of most interest.

    Correct. There is no metaborate as you've mentioned above. There
    is though Na2B2O4.8H2O which will crystallize as such from solution
    at temperatures below 53 C. Above that temperature crystalls of
    Na2B2O4.4H2O will form.

    It's likely they ship both the 4 and 8 mole products. NaBO2 and
    Na2B2O4 are used interchangeably. I could only guess why that
    is so.
     
  18. Helen B

    Helen B Member

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    'At the borax site choose, products and services, then, our products.
    VIEW both the 4 and 8 mole technical info. Stability and solubility
    are of most interest.'


    ...or just click on the link I gave at the start of this discussion to go there directly, but may as well give again here:

    4 Mol

    8 Mol
     
    Last edited by a moderator: Sep 26, 2004
  19. gainer

    gainer Subscriber

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    Anyway you look at these sites, the number of atoms of Na, B, H, and O that you get by weighing out a gram is the same for either the 4 Mol or the 8 Mol. In solution the water of crystallization just increases the amount of water.

    I doubt that the chance of getting anhydrous NaBO2 when you order sodium metaborate are very good. I could be wrong. It seems I have been wrong a lot lately.

    I had the temperature ranges backward.