Sodium thiosulfate--anhy or penta?colourless crystalline

Discussion in 'Darkroom Developing and Printing' started by QueenAdelle via PhotoKB.com, Oct 7, 2006.

  1. I just bought sodium thiosulfate from a chemical store. The label did not
    indicate whether it was anhydrous or pentahydrate. I asked the store and they
    said it was not indicated either. The chemical is from China. The detail is
    only: sodium thiosulfate, 99% photo grade.

    What I have here are big colourless crystals/granules. Does anyone here have
    an idea whether this is anhy or penta? What are the differences in appearance
    between sodium thiosulfate anhydrous and sodium thiosulfate pentahydrate?

    I am still researching, but it will be a great help if someone here could
    give me their advice. I hope someone can answer this question.

    Thanks.

    --
    +Adelle ~

    Message posted via PhotoKB.com
    http://www.photokb.com/Uwe/Forums.aspx/photo-darkroom/200610/1
     
    QueenAdelle via PhotoKB.com, Oct 7, 2006
    #1
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  2. QueenAdelle via PhotoKB.com

    Guest

    RE: QueenAdelle via PhotoKB.com wrote:
    >
    > I just bought sodium thiosulfate from a chemical store.
    >


    The penta will chill the water when dissolved. Test
    with a tbl spoon in 1/2 cup of room temperature water.
    I think a drop of as much as 20 degrees F might be
    expected. Dan
     
    , Oct 7, 2006
    #2
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  3. "QueenAdelle via PhotoKB.com" <u15922@uwe> wrote

    > I just bought sodium thiosulfate from a chemical store.
    > The label did not indicate whether it was anhydrous or
    > pentahydrate. The chemical is from China. The detail is
    > only: sodium thiosulfate, 99% photo grade.


    Anhydrous chemicals are not all that common for photographic/
    general use as they absorb moisture from the air and cake up.
    If the chemical is to be added to water anyway there is no
    reason to use the anhydrate, as such 'photo grade' will be
    hydrated.

    A good indicator is the packaging it comes in: if it is
    a plastic bag/paper box/LDPE jar it is hydrated [or
    soon will be].

    > What I have here are big colourless crystals/granules.


    That's the normal hydrated photographic 'hypo'. Just
    use it wherever hypo/thiosulfate is called for.

    --
    Nicholas O. Lindan, Cleveland, Ohio
    Darkroom Automation
    http://www.nolindan.com/da/index.htm
    n o lindan at ix dot netcom dot com
     
    Nicholas O. Lindan, Oct 7, 2006
    #3
  4. You have pentahydrate sodium thiosulfate, based on the physical description.

    Try it in a fixer formula on that assumption. If fixing time is grossly
    shorter than expected, then assume it is anhydrous, but I think not. It's
    been a few years since nearly every photo store sold brown bags of the
    pentahydate out of bulk as fixer, but it has a granulaer character you don't
    forget.

    "QueenAdelle via PhotoKB.com" <u15922@uwe> wrote in message
    news:67662ed50109f@uwe...
    >I just bought sodium thiosulfate from a chemical store. The label did not
    > indicate whether it was anhydrous or pentahydrate. I asked the store and
    > they
    > said it was not indicated either. The chemical is from China. The detail
    > is
    > only: sodium thiosulfate, 99% photo grade.
    >
    > What I have here are big colourless crystals/granules. Does anyone here
    > have
    > an idea whether this is anhy or penta? What are the differences in
    > appearance
    > between sodium thiosulfate anhydrous and sodium thiosulfate pentahydrate?
    >
    > I am still researching, but it will be a great help if someone here could
    > give me their advice. I hope someone can answer this question.
    >
    > Thanks.
    >
    > --
    > +Adelle ~
    >
    > Message posted via PhotoKB.com
    > http://www.photokb.com/Uwe/Forums.aspx/photo-darkroom/200610/1
    >
     
    Randy Stewart, Oct 7, 2006
    #4
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