DrChemistRabbit
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Preparation of elemental Bromine
Last weekend I successfully get some bromine from its salts.
I mixed KBr with MnO2and put them into a flask.then I add some H2SO4and turn on the heater.Bromine vapour went
through the condenser tube and liquefied.
2KBr + MnO2 + 2H2SO4 ==Br2↑ + MnSO4 + K2SO4 + 2H2O
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Brain&Force
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Nice work! You can also make chlorine by adding a mixture of H+ and Cl- to MnO2; it is highly advisable to use a fume
hood.
I've never made bromine, but I've read the best place to store it is in the freezer. This should help condense it all.
At the end of the day, simulating atoms doesn't beat working with the real things...
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DrChemistRabbit
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Quote: Originally posted by Brain&Force  | Nice work! You can also make chlorine by adding a mixture of H+ and Cl- to MnO2; it is highly advisable to use a fume
hood.
I've never made bromine, but I've read the best place to store it is in the freezer. This should help condense it all. |
yes,bromine is very volatile,but under -8℃ it will be solid and volatilize slowly.I didn't store it in freezer,I store it under the cover of
water.the best way to store bromine is sealing in ampoule.
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numos
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The method I use is cheaper, (doesn't require H2SO4).
HCl+NaBr, then redox with Ca(ClO)2.
First picture: my three different attempts, the same quantity of reactants was used each time, I can proudly say my yield improved greatly! 
Other pics: my most recent attempt (did that today actually)
I do have to say be careful with this reaction, your method seems to give a calmer reaction, on my first attempt the Ca(ClO)2 reacted so furiously it
gave a coke + mentos fountain - except with a vile mixture of acids and Bromine gas. I ran - hence the tiny yield, just thought I'd share my story.
Also anyone know how to safely dispose of the by product? I'm thinking dilute the f* out of it and flush it down the toilet, but I'm not sure that's
what one is supposed to do... For now the stuff is sitting in glass jars.
Still congrats on the Bromine isolation! It is a pretty rewarding reaction.
As for storage, ampules work fine, I haven't found a need to refrigerate it, last thing I want is for someone to eat an unusually flavored
Popsicle.
Amercian science surplus has some on the cheap:
http://www.sciplus.com/p/AMPULE-5ML_33342
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DrChemistRabbit
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| Quote: Originally posted by numos | The method I use is cheaper, (doesn't require H2SO4).
HCl+NaBr, then redox with Ca(ClO)2.
First picture: my three different attempts, the same quantity of reactants was used each time, I can proudly say my yield improved greatly!
Other pics: my most recent attempt (did that today actually)
I do have to say be careful with this reaction, your method seems to give a calmer reaction, on my first attempt the Ca(ClO)2 reacted so furiously it
gave a coke + mentos fountain - except with a vile mixture of acids and Bromine gas. I ran - hence the tiny yield, just thought I'd share my story.
Also anyone know how to safely dispose of the by product? I'm thinking dilute the f* out of it and flush it down the toilet, but I'm not sure that's
what one is supposed to do... For now the stuff is sitting in glass jars.
Still congrats on the Bromine isolation! It is a pretty rewarding reaction.
As for storage, ampules work fine, I haven't found a need to refrigerate it, last thing I want is for someone to eat an unusually flavored
Popsicle.
Amercian science surplus has some on the cheap:
http://www.sciplus.com/p/AMPULE-5ML_33342
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that seems great…I think there is a disadvantage in your method.the reaction between HCl and Ca(ClO)2 will produce chlorine,if chlorine
and HCL were excessed,the bromine will be polluted by chlorine.my method doesn't produce any other impurities except water
also,you can use a more efficient condenser,I noticed that you use a straight tube condenser,you can try spherical or serpentine condenser,because the
b.p. of bromine is 58℃
[Edited on 2014-3-8 by DrChemistRabbit]
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blogfast25
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| Quote: Originally posted by DrChemistRabbit | that seems great…I think there is a disadvantage in your method.the reaction between HCl and Ca(ClO)2 will produce chlorine,if chlorine
and HCL [sic] were excessed,the bromine will be polluted by chlorine.
[Edited on 2014-3-8 by DrChemistRabbit] |
Preparing bromine with possible chlorine present is a recipe for interhalogens like BrCl, which are difficult to get rid of.
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numos
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| Quote: Originally posted by DrChemistRabbit |
I think there is a disadvantage in your method.the reaction between HCl and Ca(ClO)2 will produce chlorine,if chlorine and HCL were excessed,the
bromine will be polluted by chlorine.my method doesn't produce any other impurities except water |
Agreed, and I believe that was also partly responsible for the vigorous reaction, that's why in the two latter attempts NaBr solution was strongly
excessed.
For your method do you use conc. H2SO4 or will 35% work fine? Will NaBr work well for your method?
Also,the condenser you are using - Allihn condenser right? Doesn't the Bromine get stuck in the bulbs? Seems it would work better as an upright
condenser
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DrChemistRabbit
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| Quote: Originally posted by numos | | Quote: Originally posted by DrChemistRabbit |
I think there is a disadvantage in your method.the reaction between HCl and Ca(ClO)2 will produce chlorine,if chlorine and HCL were excessed,the
bromine will be polluted by chlorine.my method doesn't produce any other impurities except water |
Agreed, and I believe that was also partly responsible for the vigorous reaction, that's why in the two latter attempts NaBr solution was strongly
excessed.
For your method do you use conc. H2SO4 or will 35% work fine? Will NaBr work well for your method?
Also,the condenser you are using - Allihn condenser right? Doesn't the Bromine get stuck in the bulbs? Seems it would work better as an upright
condenser |
I used conc.sulfuric acid,it's also an absorbent in the reaction.as for the bromide,you can use NaBr too,it won't affect the reaction.
bromine is not viscous,just lift the condenser the bromine will all flow down.
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subsecret
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IIRC, bromine can be kept under concentrated sulfuric acid, as they don't react, and can also be dried with this acid. Take extreme caution when
drying bromine with sulfuric acid in a separatory funnel, as heat can build up very quickly.
Very nice work.
Fear is what you get when caution wasn't enough.
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MrHomeScientist
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Sooo many threads on making bromine. I absolutely love the element and reading about people's preparations of it, but let's try searching first and
combining threads eh? Maybe there should be a stickied "bromine preparation" thread.
Anyways every time this is brought up again, I feel compelled to share the electrolysis method since very few people seem to know about it. I found
the procedure on woelen's site, and made a 2-part video of it here: http://www.youtube.com/watch?v=NKjyM2AkZSY
It's very simple - uses only OTC pool chemicals (except potassium dichromate), and an electrolysis setup with graphite electrodes. The oxidizer,
sodium bromate, is created in-situ by the electrolysis. It also greatly cuts down on vapors. The downside is that it takes quite a while to
electrolyze - 26 hours in my case. Lots of fun though. Nice work on everybody else's preps!
DrChemistRabbit: cooling your receiver in an ice bath will help condense the vapor and improve your yield.
numos: I agree with blogfast in trying to remove chlorine from bromine preps - interhalogen contamination is very difficult to
remove!
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subsecret
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MrHomeScientist, can anything besides potassium dichromate be used as an oxidizer?
The pipettes in the picture below could be used as ampoules...
They hold a greater volume than the average ampoule, and are thick-walled.
Fear is what you get when caution wasn't enough.
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DrChemistRabbit
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| Quote: Originally posted by MrHomeScientist | Sooo many threads on making bromine. I absolutely love the:-C element and reading about people's preparations of it, but let's try searching first and
combining threads eh? Maybe there should be a stickied "bromine preparation" thread.
Anyways every time this is brought up again, I feel compelled to share the electrolysis method since very few people seem to know about it. I found
the procedure on woelen's site, and made a 2-part video of it here: http://www.youtube.com/watch?v=NKjyM2AkZSY
It's very simple - uses only OTC pool chemicals (except potassium dichromate), and an electrolysis setup with graphite electrodes. The oxidizer,
sodium bromate, is created in-situ by the electrolysis. It also greatly cuts down on vapors. The downside is that it takes quite a while to
electrolyze - 26 hours in my case. Lots of fun though. Nice work on everybody else's preps!
DrChemistRabbit: cooling your receiver in an ice bath will help condense the vapor and improve your yield.
numos: I agree with blogfast in trying to remove chlorine from bromine preps - interhalogen contamination is very difficult to
remove! |
I'd like to know about the electrolyze method,but…I'm in China,so I can't visit yutube or many other sites  what a pity! And thank you for your advice,I am trying to improve my experiment.
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MrHomeScientist
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Awesomeness: You should watch the video (or see the link
below) Dichromate isn't the oxidizer - the bromate produced by electrolysis is. Only half a gram of dichromate is added to increase efficiency of the
cell, by preventing the back-reduction of bromate back to bromide.
DrChemistRabbit: Here's woelen's webpage on the method that I based my video off of: http://woelen.homescience.net/science/chem/exps/OTC_bromine/...
I followed his procedure pretty much exactly, and got a very similar yield.
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Metacelsus
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I prefer electrolysis as well (electricity is cheap!).
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DrChemistRabbit
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yes,electrolysis is cheaper,but it cost more time.I have one gallon of sulfuric acid,and manganese dioxide isn't expensive.I don't care about the cost
of a small experiment.
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