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    Made up some NaOH for titration practice a lil while ago (an entire litre of the stuff). Used distilled/deionized water, tested it for pH before mixing, used cleaned standard flask, bottles, stirrers, the whole shebang.

    Then I went to actually do one of these titrations. Pippetted 20cc into a conical flask, added Universal Indicator, went to get a sheet of paper (for a background), came back and WTF!!! My nice purple pH 12 coloured NaOH was a nasty green pH 7.

    So i assumed i had done something wrong and remade everything using equipment triple-rinsed in deionized water. Same result.

    Any ideas? I think the NaOH pellets might be off, but it only neutralises when in contact with the air - I put some in an airtight test tube with some UI and nothing happened. Also repeated all with Methyl Orange and phenylthalein, same result.

    THEN I tested some of the other NaOH. They were from a variety of storage cupboards, all sealed containers, mostly standard 1.0mol.dm^3 bench solutions used in practical tests, some 2.0mol.dm^3. Same problem. Now, we didn't have this problem last year, all the NaOH was fine. No other chemicals have been affected.

    :confused::confused::confused:
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    (Original post by UpsidedownLandMan)
    Made up some NaOH for titration practice a lil while ago (an entire litre of the stuff). Used distilled/deionized water, tested it for pH before mixing, used cleaned standard flask, bottles, stirrers, the whole shebang.

    Then I went to actually do one of these titrations. Pippetted 20cc into a conical flask, added Universal Indicator, went to get a sheet of paper (for a background), came back and WTF!!! My nice purple pH 12 coloured NaOH was a nasty green pH 7.

    So i assumed i had done something wrong and remade everything using equipment triple-rinsed in deionized water. Same result.

    Any ideas? I think the NaOH pellets might be off, but it only neutralises when in contact with the air - I put some in an airtight test tube with some UI and nothing happened. Also repeated all with Methyl Orange and phenylthalein, same result.

    THEN I tested some of the other NaOH. They were from a variety of storage cupboards, all sealed containers, mostly standard 1.0mol.dm^3 bench solutions used in practical tests, some 2.0mol.dm^3. Same problem. Now, we didn't have this problem last year, all the NaOH was fine. No other chemicals have been affected.

    :confused::confused::confused:
    NaOH doesn't really "go off". I suspect your indicator is faulty.
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    (Original post by Plato's Trousers)
    NaOH doesn't really "go off". I suspect your indicator is faulty.
    All three of them? The Methyl Orange is brand new.
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    (Original post by UpsidedownLandMan)
    All three of them? The Methyl Orange is brand new.
    What you have described is simply not possible in the real world...

    Therefore:

    1. Somebody has switched your sodium hydroxide (call the boss)
    2. You are suffering hallucinations (call the doctor)
    3. The laws of chemistry do not work in your laboratory (call NASA)
    4. You have been possessed by the devil (call a priest)
    5. Whoever is operating the matrix in 'the land of under' is having a laugh (call Nemo)
    6. You're telling porky pies (call me a taxi)
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    (Original post by charco)
    What you have described is simply not possible in the real world...

    Therefore:

    1. Somebody has switched your sodium hydroxide (call the boss)
    2. You are suffering hallucinations (call the doctor)
    3. The laws of chemistry do not work in your laboratory (call NASA)
    4. You have been possessed by the devil (call a priest)
    5. Whoever is operating the matrix in 'the land of under' is having a laugh (call Nemo)
    6. You're telling porky pies (call me a taxi)
    charco, my friend, you have excelled yourself this time!

    :rofl:

    (Please rate some other members before rating this member again.)
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    repped for lols. But seriously... it's starting to annoy me!!!
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    Indicators are a complex mixture of buffer solutions. As such they are prone to malfunctioning, particularly if they've been mixed wrongly so that one of the reactions has the position of equilibrium too far to one side.

    The likelihood is that your indicators are faulty. Test them with strong and weak acids as well, and a weak base (ammonia solution) and see what happens.
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    (Original post by UpsidedownLandMan)
    repped for lols. But seriously... it's starting to annoy me!!!
    maybe it's because you are in New Zealand - everything's upside down there, presumably
 
 
 
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