Bromine from BCDMH

  • Thread starter Cesium
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Main Question or Discussion Point

I am trying to isolate bromine from 1-Bromo-3-Chloro-5,5-Dimthylhydantoin (BCDMH used for pools). I would assume I could do this by passing chlorine gas through an aqueous solution but it is not soluble in water. Since this is used in pools, it must eventually dissolve/decompose so maybe then it would work. Any other possible methods? Molten state?

By the way, I can't find any NaBr tablets.
 

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  • #2
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Apparently, these tablets slowly dissolve in water forming hypobromous and hypochlorous acid. So I can just heat the resulting solution and condense Br, right?
 
  • #3
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Ok, so I heated up a tiny bit of this 1-Bromo-3-Chloro-5,5-Dimthylhydantoin. I got tons of chlorine and a bright red liquid. I intially thought this was bromine, but upon cooling it turned into a very viscous liquid that is not volatile like bromine. Any ideas on what this could be? What is an easy way to test if I have bromine?
 
  • #4
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Bromine, at last!

After doing some experimenting, I'm reactivating this thread to report that I have successfully prepared a small amount of bromine from BCDMH (1-Bromo-3-Chloro-5,5-Dimethylhydantoin). BCDMH is not soluble in water, but it reacts with boiling water to give hypochlorous and hypobromous acids.

C5H6BrClN2O2 + 2H2O --> C5H8N2O2 + HClO + HBrO

I dissolved 15g of BCDMH in about 200 mL boiling water. Most of the BCDMH seemed not to react. It just floated and frothed up to the top of the container. The solution, however, turned a deep yellow golden color and smelled very much like bleach. I skimmed off the froth with a spoon and decanted the liquid from the unreacted solid at the bottom of the container. I then added about 20 mL 50% sulfuric acid to the solution while it was still hot and the solution immediately turned orange-red. A liquid distilled off at around 60C. The hardest part was condensing the bromine. I cooled my receiving container in a salt-ice bath, but it seemed as if a lot of gas was escaping (although a substantial volume of this may have been chlorine also produced by the reaction). When I disassembled my apparatus, the flask fumed profusely but I saw a red solid stuck to the bottom of the container. I scraped this off and tried my best to pour it in a container. By the time I found my camera, most of it evaporated and had mixed with water condensation, giving orange-red bromine water. The inside of my PVC distillation set up is now stained a bright red. Does anybody know of any clever ways of storing bromine? Glass containers will work but it will eat through any plastic lid.
 

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  • #5
Hootenanny
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Cesium said:
Glass containers will work but it will eat through any plastic lid.
Use a glass stopper then :wink:
 
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Would it be okay to distill bromine in a copper vessel? "Copper and chlorine do not react rapidly at room temperature", so I am thinking bromine ought to be alright. One MSDS I found says that bromine "may" corrode copper. I suppose that bromine and copper won't react at room temperature, but what will bromine vapor do to copper?
 
  • #7
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Glass Factor

What properties of glass make it suitable for lining the bromine storage tank? :confused:

Why do you suppose that lead is preffered for lining the lorry tanks? :yuck:

All suggestions welcome :tongue:
 
  • #8
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It would be easier to use 1,3-Dibromo-5,5-dimethylhydantoin, DBDMH, since it releases only bromine and not bromine and chlorine. These tablets are often used in spas (though BCDMH is also used in spas). Adding acid will produce bromine gas (just as adding acid to a chlorine solution produces chlorine gas). Another alternative is do create a solution of bromide, say from sodium bromide, and then use electrolysis to produce bromine gas at the anode. I assume that with a sufficient concentration of bromide you can get mostly bromine gas instead of oxygen gas (from electrolysis of water). At the cathode, hydrogen gas will be produced.

Richard
 

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