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Cou
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Separating bromine gas from water vapor
I was able to make bromine by sodium bromide and concentrated sulfuric acid, and now it's brown gas, but it is also suspended in water vapor and when
i put the flask in the freezer, it doesn't liquefy.
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vulture
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Thread Moved
26-10-2013 at 12:51 |
vulture
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Can you be a little more specific about what's going on: reaction conditions and amounts of reagents?
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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Cou
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I'm too lazy to use stochiometry, so first I poured in some sodium bromide, then sulfuric acid on top of it. It made this cloudy brown gas, which I
assume is bromine and water vapor, and when I put it in the freezer, the bromine didn't condense.
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Pyro
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That's not the attitude to have when you are making Br2 (look who's talking  )
how dark is your gas? can you post a pic?
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deltaH
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Hi Cou, you can't make bromine that way, you would have made hydrogen bromide gas which only liquefies at -86.9C!
To make bromine, you need oxidising conditions. Your equation is:
H2SO4(l) + NaBr(s) => NaHSO4(s) + HBr(g)
You should be able to dissolve the gas in water to form hydrobromic acid.
[Edited on 26-10-2013 by deltaH]
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bismuthate
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I believe that that makes HBr not Bromine. Also' please do that outside not inside.
Try NaOCl+NaBr+HCl
EDIT oops deltaH posted while I typed sorry.
[Edited on 26-10-2013 by bismuthate]
[Edited on 26-10-2013 by bismuthate]
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kristofvagyok
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Maybe it would be a good idea for you to study a bit more chemistry than messing with chemicals.
I have a blog where I post my pictures from my work: http://labphoto.tumblr.com/
-Pictures from chemistry, check it out(:
"You can’t become a chemist and expect to live forever." |
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deltaH
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If I'm not mistaken, pyro here is SM's resident bromine making expert  So ask nicely...
@bismuthate... yeah don't you just hate it when that happens? I know I do!
[Edited on 26-10-2013 by deltaH]
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Pyro
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You can make Br2 with NaBr and H2SO4.
it proceeds like this:
NaBr + H2SO4 -> Na2SO4 + Br2 + H2O + SO2
H2SO4 + NaBr -> NaHSO4 + HBr
2SO2+2H2O+2HBr->H2SO4+2Br2
If i'm not mistaken.
but lots of NaBr is wasted as HBr. It's a very inefficient method
CORRECTION:
2NaBr + 2H2SO4 -> Na2SO4 + Br2 + 2H2O + SO2
H2SO4 + NaBr -> NaHSO4 + HBr
2SO2+2H2O+2HBr->2H2SO4+Br2
[Edited on 26-10-2013 by Pyro]
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deltaH
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Ah ok, so sulfuric acid acts as the oxidant? Interesting, always thought that was kinetically useless. Hmm... well I learnt something new today...
sorry cou looks like you can make some bromine that way.
Pyro, there's a problem with your last equation...
| Quote: | | 2SO2+2H2O+2HBr->H2SO4+2Br2 |
Your first equation is also not balanced.
Ok, just checked out reduction potential tables, for sulfurc acid:
SO42- + 4 H+ + 2 e− <=>SO2(aq) + 2 H2O E=+0.17V
For bromine:
Br2(l) + 2 e− <=> 2 Br- E=+1.066V
So I don't see how you can make any bromine from the reduction of sulfuric acid to SO2?!
[Edited on 26-10-2013 by deltaH]
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woelen
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No, it is not a good method of making bromine. If you add NaBr or KBr to conc. H2SO4, then most of the bromine will escape as HBr and only a small
part as Br2, while at the same time SO2 is formed. So, basically, you get a mix of mostly HBr, with some Br2 and some SO2 in it. There is enough Br2
though to see a clearly visible orange/brown color in the gas-mix.
When this gas mix comes in contact with water, then the SO2 and Br2 react again, to give H2SO4 and HBr. The fact that SO2 is more volatile than Br2
may lead to escape of some SO2, while Br2 remains behind. So, in practice, you get a little left-over Br2 in your water, with larger amounts of HBr
and some H2SO4.
Summarizing: A useless crap method of making Br2.
I suggest you to use the search engine, use Google and use site:sciencemadness.org as part of your search query to limit search results to
sciencemadness.org.
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bismuthate
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I see how could work. However there are many a thread on this.
P.S. as deltaH said where would the other sulfur atom go? This could be an intesesting reaction to react dry HBr an SO2.
Edit Would this reaction Work with SO3 or 03 or other gaseous oxidisers (I believe it would) ?
[Edited on 26-10-2013 by bismuthate]
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deltaH
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Ah... interesting woelen, so you definitely make some Br2 though, is it that the extremely acidic conditions shift that sulfate
reduction half reaction so much that it works? That's pretty impressive, a whole volt shift!
Now I'm curious to work out what the reduction potential of 98% H2SO4 is... and I understand why blogfast25 said that he's conc.
H2SO4 was too oxidising in his attempt to produce Ti alum.
[Edited on 26-10-2013 by deltaH]
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Cou
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So what is a better way of making bromine? I remember reading a method that uses electrolysis, sodium bisulfate and sodium dichromate but I can't find
it
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bismuthate
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Bubble chlorine through NaBr, or as I said before mix HCl, bleach and NaBr. There are a ton of videos on youtube U2U me or post here if you want one.
The electrolysis will be relatively hard I believe.
Oh yeah by the way here is the video for the way you mentioned which was made by mrhomescientist, a member of SM
http://www.youtube.com/watch?v=NKjyM2AkZSY
[Edited on 26-10-2013 by bismuthate]
[Edited on 26-10-2013 by bismuthate]
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Pyro
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oops,
I'll edit it. I misplaced the 2. it should be 2H2SO4+Br2.
thanks
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Random
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Quote: Originally posted by deltaH  | If I'm not mistaken, pyro here is SM's resident bromine making expert So ask nicely...
@bismuthate... yeah don't you just hate it when that happens? I know I do!
[Edited on 26-10-2013 by deltaH] |
You know alot about forum members for 1.5 month old account. Perhaps this account wasn't the first one?
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Metacelsus
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When I isolated bromine, I electrolyzed my sodium bromide until 1/6 of it was converted to sodium bromate, and then added sulfuric acid:
5 Br- + BrO3- + 6 H+ -> 3 Br2 + 3 H2O
My yield from 103 g NaBr was 25 ml of bromine, which is near theoretical.
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bismuthate
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Random I don't recognize him so he may have just been watching, this is most likely his first. I did for a year before I signed up.
Cheddite Cheese how long did it take and how much did you use?
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Pyro
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http://www.youtube.com/watch?v=AL9ehxTaYRs
Br2 by KMnO4+NaBr+H2SO4 (I do it like this
http://www.youtube.com/watch?v=OB4MmPTOBxg
Br2 by NaBr soln. and Cl2
http://www.youtube.com/watch?v=6L7hIWZzWE8
Br2 by NaBr+H2SO4
http://woelen.homescience.net/science/chem/exps/raw_material...
Br2 by KBr+KBrO3+H2SO4
http://www.sciencemadness.org/talk/viewthread.php?tid=13104
SM's own writeup on making Br2. Written by Magpie
[Edited on 26-10-2013 by Pyro]
[Edited on 26-10-2013 by Pyro]
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Metacelsus
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The electrolysis took 12 hours (overnight). The distillation of the bromine from the acidified solution took about 45 minutes. I ampouled the bromine,
but when I was flame sealing the (cheap) ampoule the glass cracked and some spilled on my hand. I was able to save most of the bromine, though, and
the bromine burn I got has healed completely.
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WGTR
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Here was my experience:
For about 1mL of liquid bromine (think carefully if you want to isolate more of this
at one time):
Make a saturated solution of NaBr in about 200mL of ice cold water that is kept on
an ice bath.
With graphite electrodes, electrolyze the solution. Make sure that the bottom of
the anode is close to the bottom of the beaker. The cathode can be up near the
top of the solution.
As the solution is electrolyzed, a bromine-colored solution will run off the anode
and settle to the bottom. Don't disturb this layer as it forms.
The current needs to be adjusted to as high a level as possible without forming
oxygen bubbles on the anode. No gas bubbles should be formed on the anode.
Bromine is quite a bit soluble in NaBr solution (much less so in pure water), but as
this bromine-containing layer saturates, tiny bromine droplets will start flying off
the end of the anode, and collecting in a tiny puddle. Make sure that this little
puddle is close by to the tip of the anode (so the bromine doesn't dissolve so
much), but not directly touching it.
There is a limit to how much bromine you can get at one time with this solution, as
sodium hypobromite begins to form as the solution becomes significantly
alkaline. Once this happens, your anode starts to deteriorate.
After a sufficient amount of time (several hours), you should have enough product
to be able to pipette the bromine liquid from the small puddle at the bottom of the
beaker, and transfer it to a small container with pure water in it. As long as the
water is kept below the boiling point of bromine, the bromine's limited water
solubility will keep it sitting happily at the bottom for a considerable time (maybe
not long enough for permanent storage, but certainly long enough for you to use
it).
For extra credit, you can pipette the bromine-rich NaBr solution to a boiling flask,
and gently distill the extra bromine out of the solution. Dark bits of Br2 will start
coalescing in the condenser, and can be collected in cold water.
[Edited on 26-10-2013 by WGTR]
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deltaH
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random, I beleive it had something to do with the romanians...
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Pyro
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well, yes. but I have a history with Br2
In my mind it's the second coolest thing I have, the coolest being P4!
see: http://www.sciencemadness.org/talk/viewthread.php?tid=22645#...
that plante1999 so gentlemanly posted without my permission.
(jeez, makes me look incompetent  , just one fuck up after another, seems fate isn't
on my side)
[Edited on 26-10-2013 by Pyro]
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deltaH
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Don't worry Pyro, we've all had our moments, I've had many worse lol
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