Derek McOlund
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HBr from BCDMH
I recently bought some bromine pellets for swimming pools, on the label it says it contains bromochloro-5 5-dimethylimidazolidine-2 4-dione. Does
anyone know how to make hydrobromic acid out of it? On the side of the label it says: "Forms toxic gases on contact with acids" could the gases
they're referring to be HBr? In that case, to make hydrobromic acid I'd just have to react the BCDMH with sulphuric acid to form HBr gas?
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A Halogenated Substance
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BCDMH produces a mixture of chlorine and bromine gasses when acid is added to them.
According to the wiki, it hydrolyzes to hypobromous and hypochlorous acids so the reaction with acid with this is sorta similar to with acid and
bleach (except dimethylhydantoin is produced on the side).
https://en.wikipedia.org/wiki/BCDMH
This paper details the decomposition of hypochlorous acid to hydrochloric acid.
http://www.nrcresearchpress.com/doi/pdf/10.1139/v52-107
Perhaps you could try to adapt a method for a "hydrobromous acid to hydrobromic acid" adaption?
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j_sum1
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Which begs the question, is there a straightforward route from BCDMH to Br2? BCDMH is, to my knowledge, the only OTC source of bromine available in
my area.
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JJay
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There is; I have a book called Small Scale Synthesis of Laboratory Reagents (which I believe was written by an SM member) that gives a procedure for
making bromine from BCDMH: https://books.google.com/books?id=VqosZeMjNjEC&lpg=PP1&a...
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j_sum1
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Ah! Len. I might have guessed. He is surely missed around here. His book is excellent by all accounts but I have never seen a copy and whenever I
have looked it has been out of my price range.
I did not know the text was accessible online. Thanks.
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A Halogenated Substance
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The first time I attempted to produce bromine from this compound, I directly added hydrochloric acid to a slurry of it (looking back it probably just
helped form more bromochloride) which I suspect released both chlorine and bromine gasses (resulting in even more bromochloride).
After a distillation, I received a product that looked similar to bromine but vaporized in seconds, even in an ice bath.
Looking back, I may even have been better off just straight up adding chlorine gas directly to a slurry of BCDMH with strong stirring...
I didn't even manage to recover less than a milliliter of bromine (or even the bromochloride for that matter). 
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Also thanks for the book link JJay! I definitely be taking a longer look in it some time. 
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