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  1. #1
    kb3lms's Avatar
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    Sodium Metabisulfite vs Sodium Sulfite

    My supply of sodium sulfite is running low. I have a 5 pound bag of Sodium Metabisulfite. Any way I can convert the metabisulfite for use before I order more sulfite? Is it worth doing?

    Thanks!
    All this has happened before, and all this will happen again.

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    Sodium Metabisulfite vs Sodium Sulfite

    I was on the other side of the rope, figuring out how to replace metabisulfite on a formula and the only possible substitution was sodium bisulfite. I guess you shoul order sodium sulfide right now...


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    kb3lms's Avatar
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    I guess you shoul order sodium sulfide right now...
    Lol, I guess so. Well, thought it was worth asking since IDK what to do with this metabisulfite. Maybe it will be good for the roses?

    -- Jason
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    Sodium metabisulfite can be used in the making of acidic fixers. stop bath, washing aid, and divided developers.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

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    Quote Originally Posted by kb3lms View Post
    Any way I can convert the metabisulfite for use before I order more sulfite? Is it worth doing?
    Sodium Metabisulfite is a dehydrated form of Sodium Bisulfite: 2 NaHSO3 <----> Na2S2O5 + H2O

    If you dissolve them in water, they will be the same. In aqueous solution you can convert the Sodium Metabisulfite to Sodium Sulfite by adding 2 moles of NaOH per mole of Na2S2O5.
    Trying to be the best of whatever I am, even if what I am is no good.

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    Quote Originally Posted by Rudeofus View Post
    Sodium Metabisulfite is a dehydrated form of Sodium Bisulfite: 2 NaHSO3 <----> Na2S2O5 + H2O

    If you dissolve them in water, they will be the same. In aqueous solution you can convert the Sodium Metabisulfite to Sodium Sulfite by adding 2 moles of NaOH per mole of Na2S2O5.
    This is how the Sulphite is made in a concentrated form in Rodinal manufacture.

    Ian

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    Quote Originally Posted by Rudeofus View Post
    In aqueous solution you can convert the Sodium Metabisulfite to Sodium Sulfite by adding 2 moles of NaOH per mole of Na2S2O5.
    What looks very simple on paper will be a mess when you are dealing with pound quantities of this chemical. A lot of heat will br given off and the solution may splatter when the hydroxide is added. Sodium sulfite is not that expensive. Besides you have to pay for the sodium hydroxide.
    A rock pile ceases to be a rock pile the moment a single man contemplates it, bearing within him the image of a cathedral.

    ~Antoine de Saint-Exupery

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    Rudeofus's Avatar
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    Let's all agree that mixing Sodium Metabisulfite and Sodium Hydroxide is an expensive and inconvenient substitute for Sodium Sulfite, but once you've run out you are at the mercy of whoever supplies you and this can take a few days if not more.

    Most developer recipes require substantially less than "pound quantities", therefore my substitute suggestion, with all its limitations as stated above, might work quite well for kb3lms. Depending on target pH and availability of pH metering device he might even get away with Sodium Metabisulfite and Sodium Carbonate in case he only has these.
    Trying to be the best of whatever I am, even if what I am is no good.

  9. #9
    Ian Grant's Avatar
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    Quote Originally Posted by Rudeofus View Post
    Let's all agree that mixing Sodium Metabisulfite and Sodium Hydroxide is an expensive and inconvenient substitute for Sodium Sulfite, but once you've run out you are at the mercy of whoever supplies you and this can take a few days if not more.
    It's one of the commercial ways Sodium Sulphite is manufactured, so it's a logical but less practical option. On a larger scale it's cheaper.

    Ian

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    Rudeofus's Avatar
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    Quote Originally Posted by Ian Grant View Post
    It's one of the commercial ways Sodium Sulphite is manufactured, so it's a logical but less practical option. On a larger scale it's cheaper.
    Let's all agree that those who make Sodium Sulfite commercially usually don't resort to APUG for instructions ...
    Trying to be the best of whatever I am, even if what I am is no good.

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