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  1. #1
    titrisol's Avatar
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    Kodalk, what is it/replacements

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

    Is it borax/boric acid?
    Mama took my APX away.....

  2. #2
    ann
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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. #3
    titrisol's Avatar
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    Na-Metaborate (Na-BO2)
    That gave me better hits, like this one:

    Photobinbook.com
    "Michael Gudzinowicz" <bg174@F...> wrote on Dec 22, 2000
    I've included the proportions required to make 100 g metaborate. The Kodalk
    Balanced Alkali MSDS on the EKC website indicates that it is composed of
    sodium metaborate octahydrate.

    Kodak probably had a patent for a fusion process to make the compound,
    but you don't want to go off in that direction, since you want the
    product in solution, and not as a crystaline solid.

    What you need to know is:

    100 g Kodalk (sodium metaborate octahydrate) == 40.5 g borax + 9.53 g NaOH

    How to get there is outlined below:

    Sodium metaborate (NaBO2) undergoes hydrolysis upon solution to give sodium
    hydroxide and boric acid (a very weak acid):

    NaB02 + 2 H2O <->>> Na+ + OH- + H3BO3

    Borax, the decahydrate of sodium tetraborate (Na2B4O7), may be thought of
    as being composed of two metaborate molecules and one of boric anhydride:

    Na2B4O7 == 2 NaBO2 + B2O3

    Upon dissolution, the products of metaborate from borax are as above, but
    multiplied by two below:

    2 NaB02 + 4 H2O <->>> 2 Na+ + 2 OH- + 2 H3BO3

    The boric anhydride is hydrolyzed to boric acid:

    B2O3 + 3 H2O <->>> 2 H3BO3

    Overall, the products are:

    Na2B4O7 + 7 H2O <->>> 2 Na+ + 2 OH- + 4 H3BO3

    If one were to add two mol NaOH to each sodium tetraborate, the products
    would be equivalent to those derived from metaborate:

    Na2B4O7 + 7 H2O + 2 NaOH <->>> 4 Na+ + 4 OH- + 4 H3BO3

    4 NaBO2 + 8 H2O <->>> 4 Na+ + 4 OH- + 4 H3BO3

    Molecular weights:

    Borax (sodium tetraborate decahydrate) 381.42
    Sodium metaborate octahydrate 209.82
    Sodium hydroxide 40.01

    Since two mols of NaOH are required per tetraborate:

    381.42 g borax + 80.02 g NaOH == 839.2 g metaborate octahydrate
    (all in solution)

    Or to make a quantity equivalent to 100 g sodium metaborate octahydrate:

    100 g sodium metaborate tetrahydrate == 40.5 g borax + 9.53 g NaOH
    Thanks ANN!!!
    Mama took my APX away.....

  4. #4
    Helen B's Avatar
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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 Helen B; 09-23-2004 at 11:16 PM. Click to view previous post history.

  5. #5
    titrisol's Avatar
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    soo basically the formula i found would be a double concentration of kodalk?
    Mama took my APX away.....

  6. #6
    Helen B's Avatar
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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. #7
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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.
    Gadget Gainer

  8. #8
    ThomHarrop's Avatar
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    When we run out at school we use 20 Muleteam borax from the grocery store.

  9. #9

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    Quote Originally Posted by titrisol
    What is the composition of KODALK?
    Any ways to replace it? Is it borax/boric acid?
    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. #10

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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.

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