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  1. #31
    Ian Grant's Avatar
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    Quote Originally Posted by Athiril View Post
    OP: Thiocyanate is a result from cyanide and thiosulphate used as a antidote for cyanide poisoning, so I definately wouldn't be worrying about that.
    There still needs to be a degree of caution Thiocyanates are still poisonous and altough less likely to kill you would make you very sick.

    The greater danger is someone acidifying a Thiocyanate solution with concentrated Sulphuric acid which would then react violently and release Hydrogen Cyanide vaour.

    Ian

  2. #32

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    The method I found states that the preferred pH range is 1-3 but I would like to try as wide a range as I can during testing.

    The organic cation that we use is is NH4+ in the form of NH4SCN, the SCN- is used for the purpose of stripping the Rhenium off the IX columns. Once concentrated the by boiling we can get about 50-60g/L and then after cooling to -4C we get all but about 3g/L as solid Ammonium Perrhenate.

  3. #33
    Photo Engineer's Avatar
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    No literature than I can find indicates any danger of acidification of Thiocyanates, nor is the release of Cyanide indicated except with extreme heat.

    PE

  4. #34
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    Quote Originally Posted by Ian Grant View Post
    There still needs to be a degree of caution Thiocyanates are still poisonous and altough less likely to kill you would make you very sick.

    The greater danger is someone acidifying a Thiocyanate solution with concentrated Sulphuric acid which would then react violently and release Hydrogen Cyanide vaour.

    Ian



    Quote Originally Posted by Photo Engineer View Post
    No literature than I can find indicates any danger of acidification of Thiocyanates, nor is the release of Cyanide indicated except with extreme heat.

    PE


    This --^


    Gerald I think you're thinking of Potassium Ferricyanide, and one should always look at the MSDS for what they're working with as well.

  5. #35
    Ian Grant's Avatar
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    Quote Originally Posted by Athiril View Post
    This --^
    There's no contradiction there, if concentrated Sulphuric acid and a Thiocynate solution were mixed there's sufficient heat released in a violent reaction, same goes for Ferricyanide.

    It's these considerations that need to be taken into account when storing chemicals, some wet plate workers use Cyanide solutions, and are storing cyanide salts and they need to be storing acids securely awy from the rest of their chemistry.

    Ian

  6. #36
    Photo Engineer's Avatar
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    There is a straight correlation in Ferricyanide + Acid giving cyanide with enough heat.

    Fe(CN)6 + H2SO4 = Fe2(SO4)3 + HCN (unbalanced equation - for example only)

    This simple relationship requires enough heat to overcome the complexation energy inherent in making the complex ferricyanide molecule from Iron III ions and cyanide ions.

    In the case of KSCN + H2SO4, there is a huge dfference as you have a physical bond between the S, C and N atoms to form a single tightly bonded thiocyanate molecule. In fact, literature calls this a pseudo halide, in that it reacts as one as if it were a halide ion in many cases. You need a lot of energy to split it up, and the splitup is not a direct formation of HCN.

    Under vigorous conditions, you usually get S-CN ion acting as one, but sometimes you replace the Sulfur to get the O-CN ion.

    Extreme pyrolysis will give some Cyanide, but you have to beat on it. By then, the pyrolysis of other things in your lab (because it is probably on fire and your house is burning down) will drive you out and to safety!

    PE

  7. #37

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    Extreme pyrolysis will give some Cyanide, but you have to beat on it. By then, the pyrolysis of other things in your lab (because it is probably on fire and your house is burning down) will drive you out and to safety! [/QUOTE]

    I find I have to be very careful beating on glassware when doing cyanide distillations! Too hard and the glass always breaks!
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  8. #38

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    Potassium thiocyanate is considered to be moderately toxic. Contact with the chemical or its solutions can cause skin irritation. Eye contact is particularly serious. Ingestion causes changes to the blood and thyroid gland. It will not liberate hydrogen cyanide under normal conditions.

    That being said, not all compounds containing the thiocyanate ion are stable. For example Reinecke's salt NH4[Cr(NH3)2(SCN)4].H20 will begin to release HCN from its aqueous solution in about a week or so. At temperatures above 60 C the release is quite rapid. I shared a lab with another student who used this reagent and I always knew when he was using it.

    Treat all chemicals with respect and if you cannot determine whether one is toxic or not then assume that it is toxic. Using safety goggles is always wise.
    Last edited by Gerald C Koch; 04-14-2012 at 04:45 PM. Click to view previous post history.
    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

  9. #39
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    Reinecke's salt decompses as shown here: http://www.sciencedirect.com/science...40603179850959

    It is made by fusion of molten Ammonium Thiocyanate with the chromium salt. http://en.wikipedia.org/wiki/Reinecke%27s_salt

    Fused thiocyanate reactions are known and thus the decomposition with extreme heat is not a severe problem.

    It is not overly toxic when compared with other chemicals used such as Dichromates and Selenum toners.

    What it is, is controversial due to its name and structure.

    PE

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