Sciencemadness Discussion Board

bromine

Jor - 6-3-2008 at 15:09

Hello,

Im thinking about buying some bromine.
Im cuite worried about the stories , that i is almost impossible to keep this beast of a chemical inside. It will eat through anything. So I was thinking , Let buy it from Merck, because I cant imagine Merck packs it wrong? Or is it really that nasty, that it will go through anything (I would expect Merck to put in TEFLON)? Have you guys had experience with this?

kilowatt - 6-3-2008 at 15:24

Glass is completely impervious to bromine, as are passivated metals under normal conditions (as long as the bromine is dry) like nickel or monel, chrome, titanium, etc. The difficulty in containing it is due only to its volatility. It will slowly diffuse through all but the densest grades of teflon and other plastics due to their porosity. Just keep it in a glass bottle with a ground glass stopper and some fluorosilicone grease or teflon tape to help make the seal. Refrigeration helps keep the volatility down but beware that even when a small amount leaks out the fridge will smell like bromine forever.

I'm pretty sure there is at least one thread on this site regarding ampouling bromine, which may be your best bet if you just want to keep a small amount. If you aren't using it any time soon you may as well just keep it in a salt form from such as ammonium bromide or alkali bromide, and extract it when you need it. It's MUCH easier and cheaper to buy that way too. It isn't any harder to isolate than chlorine or iodine.

The real moral of the story is that if you don't know how to store or handle it properly you probably shouldn't be using it.

ScienceGeek - 6-3-2008 at 15:33

I bought some Bromine from Aldrich, and it came in a sealed tin- can in a glass bottle with a teflon- lined cap. I store it in an airtight space, and everytime I open the door, small amounts of Bromine smell seeps out.
Although it doesn't pose a risk of inhalation, it does smell up the place.

MagicJigPipe - 6-3-2008 at 20:16

"It isn't any harder to isolate than chlorine or iodine. "

I beg to differ. Aside from fluorine and astatine, bromine is the hardest halogen to isolate. Mostly because it's a liquid.

IMO it is in this order from easiest to hardest to isolate:

Iodine
Chlorine
Bromine
Fluorine
Astatine

I've never messed with fluorine or astatine but at least fluorine can be obtained via electrolysis. I'm sure astatine would be easier to isolate but it's virtually unatainable.

kilowatt - 6-3-2008 at 20:45

My point is that it isn't that difficult, and especially not difficult enough to make it worth purchasing in elemental form when its salts are so readily available. Electrolysis in a separatory funnel followed by distillation of the liquid that sinks out works. IMO electrolysis in a membrane cell or amalgam cell followed by purification is the easiest way to isolate any halogen (except fluorine which requires a special cell at low temperature); even the popular chemical methods of iodine extraction are finicky and leave much to be desired.

Sauron - 6-3-2008 at 21:09

The volatility is a function of temperature. Refrigerate the Br2 and it is tame as a kitten. Even if you don't refrigerate (In which case you will get some diffusion losses) you chould chill the bottle in an ice bath prior to opening.

I have a 100 ml Hamilton glass syringe with PTFE Luer-lok 'needle" for transfer of this sort of thing.

woelen - 6-3-2008 at 23:43

Buying Merck bromine is NOT a guarantee for a good bottle. I read a thread on www.versuchschemie.de about really rotten bromine bottles, which were purchased from Merck. Things were so bad, that after some time, there even appeared crystals in the bromine, and that can only be a big impurity. Bromnine never forms crystals at room temperature.

I have made my bromine from bromate and bromide, using an all glass distillation setup and drying it with conc. H2SO4. I posted a thread about that some time ago, it is here on sciencemadness.

I now have appr. 200 ml of bromine in a glass bottle, with a screw-cap, which has a PTFE liner inside, and teflon tape wrapped around the rim of the bottle. It stores well, but around the cap, I notice a faint smell of Br2. Summer still has to come...

Nicodem - 7-3-2008 at 02:52

Standard Fluka reagent bottles (the brown ones with the famous blue stoppers) are great for storing bromine and other such nasties. Never noticed any leak and hold a fair amount of internal overpressure. They are also easy to find since for some reason most labs just throw them away.

YT2095 - 7-3-2008 at 06:33

Quote:
Originally posted by MagicJigPipe


I beg to differ. Aside from fluorine and astatine, bromine is the hardest halogen to isolate. Mostly because it's a liquid.

IMO it is in this order from easiest to hardest to isolate:

Iodine
Chlorine
Bromine
Fluorine
Astatine


actually I beg to differ here, Bromine is Very easy to isolate!
more so than Iodine.
in fact I would go far as to say it`s one of the "Nicer" halogens to isolate and use, and for the Most part it`s very "Well Behaved", although storage for some Can present problems.

a Nice way to do it however is to use the method Woelen has outlined on his site.
I keep a jar with the correct mixture of KBr and KBrO3 as a fine powder.
for Me this is Instant-Bromine-Just-Add-Acid.
from there you can make as Little or as Much as you like at any time and it`s done within a minute or 2.

there`s no storage issues and it will last forever like this, and if I can`t wait the 1-2 minutes for the bromine liquid to form, then I have no business being in the Lab doing Any experiment that will use it anyway! :P


edit: as for Astatine, you wouldn`t want it anyway, it`s radioactive!

[Edited on 7-3-2008 by YT2095]

woelen - 7-3-2008 at 06:41

Yes, I agree with YT2095. If you acidify the 5 : 1 molar mix of KBr and KBrO3 with a suitable amount of 30% H2SO4 (for each mol of KBrO3 use well over 3 mols of H2SO4) , then within a few minutes you have a nice blob of bromine at the bottom, which can be collected using a pipette. In this way, you isolate approximately 75% of the bromine. If you want all bromine, then you need a distillation setup.

I make the following list of ease of separation of the halogens:

1) Br2 and Cl2
2) I2
3) F2

[Edited on 7-3-08 by woelen]

MagicJigPipe - 7-3-2008 at 06:42

Okay, I suppose I meant decent amounts of pure Br2. That is much more difficult than iodine or any gas. How could it be easier than I2? I consider filtering and washing a solid the simplest of all tasks in the lab.

All I'm saying is the only halogen I have EVER had any problems getting by itself, pure, is Br2. Chlorine is easily seperated from liquid because it's a gas and iodine is easily seperated from a liquid because it's a solid. This makes perfect sense to me.

woelen - 7-3-2008 at 06:48

No, I still do not agree. Iodine is formed as a fine precipitate, which is wet. Separating it from the adhering water is not that easy, although it certainly can be done. Simply heating it in order to get rid of the water is no option, the iodine also evaporates quite a lot. You need to sublime the iodine at least two times in order to het rid of the water. I do not know a highly volatile solvent, which easily rinses off the water and does not dissolve the iodine. Stuff like ether, acetone, alcohol etc. are of no use here.

Bromine, which separates as liquid, is easily pipetted without any water. The bromine, made this way already is quite pure. Solubility of water in bromine is very low (only appr. 0.05% by weight). The biggest problem is not the water, dissolved in the bromine, but the drops of water, which always will stick to your pipette and float on top of the bromine. If you accept another 10% loss of the bromine, then you could make almost perfectly dry bromine simply by pipetting it.

Getting it really dry can be done by pouring concentrated sulphuric acid on the bromine and keeping it that way:



[Edited on 7-3-08 by woelen]

YT2095 - 7-3-2008 at 06:58

Bromine`s a gas too with a little heat (and I mean a Little!).

what do you need to get a pure Br2 liquid?

1) make it as outlined above
2) either turn it to a gas and treat like Cl2 OR...
3) pipette it out into a test tube and add conc sulphuric.

it really gives you the best of Both worlds, as the gas is Clearly visible as is the liquid.

Fl2 would be the last on the list, and I would agree with, and you may as well forget At2, think Beta decay of Polonium!

anyway, we`re going Slightly off topic here, I strongly recommend the method Woelen and I employ (and probably a good many others here too), if it aint broken... Don`t fix it!

-jeffB - 7-3-2008 at 07:32

Quote:
Originally posted by kilowatt
IMO electrolysis in a membrane cell or amalgam cell followed by purification is the easiest way to isolate any halogen (except fluorine which requires a special cell at low temperature); even the popular chemical methods of iodine extraction are finicky and leave much to be desired.


If I electrolyze NaI or KI, I produce iodine, but it immediately complexes with the remaining iodide and goes into solution. How do you isolate it?

I produced Br2 and I2 by chemical oxidation of bromides and iodides, then extracted them in CCl4. (Back in the good old days, when I had a gallon of technical CCl4, and was dumb enough to use it with mediocre ventilation.) This worked well, and the CCl4 solutions were always pretty...

Jor - 7-3-2008 at 07:59

Quote:
Originally posted by woelen
No, I still do not agree. Iodine is formed as a fine precipitate, which is wet. Separating it from the adhering water is not that easy, although it certainly can be done. Simply heating it in order to get rid of the water is no option, the iodine also evaporates quite a lot. You need to sublime the iodine at least two times in order to het rid of the water. I do not know a highly volatile solvent, which easily rinses off the water and does not dissolve the iodine. Stuff like ether, acetone, alcohol etc. are of no use here.

Bromine, which separates as liquid, is easily pipetted without any water. The bromine, made this way already is quite pure. Solubility of water in bromine is very low (only appr. 0.05% by weight). The biggest problem is not the water, dissolved in the bromine, but the drops of water, which always will stick to your pipette and float on top of the bromine. If you accept another 10% loss of the bromine, then you could make almost perfectly dry bromine simply by pipetting it.

Getting it really dry can be done by pouring concentrated sulphuric acid on the bromine and keeping it that way:



[Edited on 7-3-08 by woelen]


exactly, I made some iodine as well from KI, and it was very wet. It not that hard to isolate dry though. Just heat in an erlenmeyer with a watchglass on it, and you will het quite dry iodine on the watchglass.

MagicJigPipe - 7-3-2008 at 11:35

I still completely disagree. Bromine is a pain in the ass to isolate IMO.

"I produced Br2 and I2 by chemical oxidation of bromides and iodides, then extracted them in CCl4. (Back in the good old days, when I had a gallon of technical CCl4, and was dumb enough to use it with mediocre ventilation.) This worked well, and the CCl4 solutions were always pretty"

If Br2 is so easy to isolate, why would you need something like CCl4? Anyway, with oxidation of iodides, yields are always great. Oxidation of bromides (or electrolysis) that involves any water seems to have low yields. I see you made a small amount of Br2. But how long did that take?

Also, I have never attempted to dry I2 by this method but couldn't you used a dessicator while cooling the I2 to just above 0C? This should prevent excessive sublimation and dry it at the same time.

I always just used dry filter paper. Seems to work well. Probably not dry enough for moisture sensitive applications but still reasonably dry.

I just hate messing with Br2. It mixes with water too easily and once it does it's a pain to remove from the water.

woelen - 7-3-2008 at 11:58

No need to use CCl4. Simply use the method, mentioned above where the Br2 drops out. Easy, simple and effective. Yield of oxidation is 100%, no incomplete oxidation as mentioned by MagicJigPipe. If you have incomplete oxidation, then it is time to find a better oxidizer. Every oxidizer like chlorate, permanganate, hypochlorite, bromate completely oxidizes bromide to bromine in acidic environment. Only thing is that one should be careful using fairly precise stoichiometric amounts. Especially the chlorine-based oxidizers tend to form Cl2 when used in excess and then mixed halogen compounds and bromic acid are formed.

Fleaker - 7-3-2008 at 12:17

You'll have proof of Br2 being easy to isolate quite soon. There are ample examples already on the forum of how to make bromine, but the most direct is to use bromate, bromide, and an acid (sulfuric or hydrochloric). The reaction is almost quantitative from HBr and and bromate. Distill the bromine, dry with sulfuric in a sep funnel.

I am working on a 10 kilogram synth of bromine, it's already late, but I'm waiting on the rest of my sodium bromate to arrive. I'll probably be doing it in either a 12 or a 22L flask. It will be stored in a large 2L FETFE bottle.

[Edited on 7-3-2008 by Fleaker]

-jeffB - 7-3-2008 at 12:39

Quote:
Originally posted by MagicJigPipe
If Br2 is so easy to isolate, why would you need something like CCl4? Anyway, with oxidation of iodides, yields are always great. Oxidation of bromides (or electrolysis) that involves any water seems to have low yields. I see you made a small amount of Br2. But how long did that take?

Also, I have never attempted to dry I2 by this method but couldn't you used a dessicator while cooling the I2 to just above 0C? This should prevent excessive sublimation and dry it at the same time.

I always just used dry filter paper. Seems to work well. Probably not dry enough for moisture sensitive applications but still reasonably dry.

I just hate messing with Br2. It mixes with water too easily and once it does it's a pain to remove from the water.


As I recall, Br2 and I2 partitioned into CCl4 from the aqueous I3-/Br3- solution. But this was all thirty-odd years ago, so I may be misremembering critical details.

I had neither distillation apparatus nor dessicators at the time, and I was working with sub-gram quantities anyhow.

theobromacacao - 12-4-2008 at 05:36

I'm not sure if anyone would be interested in this, but I have acquired a 2ml ampoule of bromine which is too large for my periodic table. I was wondering if any members on here (based in UK) would be interested in this for their use and experiments? I have already approached my local university to see if they would like it for their stock, but all they wanted to do with it was store it with their waste and dispose of it!!! If anyone is interested, please let me know.

YT2095 - 12-4-2008 at 07:34

I`ll take it off your hands if it`s Free (I`ll pay postage), a 2ml would be smaller than my Current element sample.
or even do a trade if you`re after an element that I have enough of to share.

MagicJigPipe - 12-4-2008 at 16:00

I suppose once I find a cheap source of BrO3 then it will be easy for me as well. 'Till then it remains annoying.

StevenRS - 12-4-2008 at 17:48

I just oxidize bromide with 30% H2O2, using H2SO4, and the heat produced in enough to distill the bromine into a sep funnel, then I just pour out the bromine. Easy, and very dry product.

Klute - 13-4-2008 at 06:35

So you use a distn setup, but connect a sep funnel instead of a receiver flask?
Do you add the H2O2 to the KBr/NaBr and H2SO4, or H2O2 and H2SO4 to the salt?

MagicJigPipe - 13-4-2008 at 11:45

Distillation of Br2 is not easy, IMO. How does one obtain NaBrO3 for a decent price? I believe IT is a pain in the ass to synthesize, as well.

woelen - 13-4-2008 at 12:15

KBrO3 works equally well and is easily synthesized. I have a write-up on that on my website:

http://woelen.homescience.net/science/chem/exps/KBrO3_synth/...


Making Br2 from this, and distilling it, also is not difficult:

http://woelen.homescience.net/science/chem/exps/raw_material...


After distilling, you can easily dry the bromine with concentrated H2SO4 and then with a pasteur pipette the bromine can be collected from under the H2SO4. You can also keep it under the H2SO4.

Edit(woelen): Made links working again.

[Edited on 30-7-16 by woelen]

MagicJigPipe - 13-4-2008 at 14:39

Yeah, I was afraid that's how it was done. Thank you very much woelen!

I have two issues with electrolysis. When I use graphite electrodes the anode disintegrates. If I use anything easily obtainable like copper, stanless steel or aluminum, well you know how that ends.

Also, I don't have dichromates although I can get some easily.

I'm sure this is no big deal but I also don't have access to cheap KBr, only NaBr.
Quote:

One could make some chromate by adding potteries green chromium oxide to some sodium hydroxide and some potassium nitrate. Melting this mix results in formation of yellow chromate. A small amount of this yellow material can be dissolved in 30 ml of water, and then carefully hydrochloric acid is dripped in, until the pH is around 7. In this solution one then dissolves the KBr. The small amount of chloride and possibly nitrate, introduced in this way, is not of any concern.

This is interesting as I have all of the required reagents.

As you can see, however, my disdain for Br synthesis compared to other halogens remains. This is because well, just look at all the trouble I would have to go through. I could create 100g of I2 or several moles or more of Cl2 in the time it would take me to just synthesize the bromate. (I2 = KI, H2O2, H2SO4 Cl2=NaHSO4, NaClO... Br2=Carbon rods, Na/KBr,K2Cr2O7, Power source, time then H2SO4)

I don't know why but I still find I2 and Cl2 so much easier to obtain. I appreciate everyones help with finding an easier way to make Br2, though. Otherwise I would be in a bad mood every time I made it ;)

We should have a "cook off" to see how fast either one of us could make reasonably dry I2 versus Br2. I honestly believe I would be a good contender with the I2.

woelen - 13-4-2008 at 15:01

Quote:
We should have a "cook off" to see how fast either one of us could make reasonably dry I2 versus Br2. I honestly believe I would be a good contender with the I2.

Depends on the precursors. If you start with H2O2, KI and HCl, and I would start with H2O2, KBr and HCl, yes, then you win.

But even then, once you have the right precursors, making bromine is not that difficult. Also, making the precursor KBrO3 can be a rewarding activity on its own. KBrO3 is an interesting chemical itself, it is a very energetic oxidizer, which also is good for many spectacular pyro-experiments.

Of course, if your goal is to make bromine, then you do not need to go all the way through dry and pure KBrO3. In that case, you could electrolyse your concentrated NaBr solution (with a tiny pinch of chromate or dichromate), such that appr. 1/6 of all bromide is converted to bromate. The next step then is adding 50% H2SO4 to your solution (no need to purify, no need to isolate anything) and stir. The bromine will drop out in the form of many small droplets and with a pasteur pipette you can isolate it. Yield will be appr. 75%. If you have a distillation setup, then yeild can be nearly quantitative.

If you wish, I can do the math for you on how long you need to electrolyse at what current, given the amount of NaBr.

MagicJigPipe - 13-4-2008 at 16:21

I kind of want to go ahead and try that. I wish there was an OTC source of dichromate (on a Sunday) so I wouldn't have to do the melt process or wait for the dichromate to be delivered.

I have dabbled in electronics in the past so I still have a "kit" full of resisters, capacitors, transisters etc... I don't have any "large" resistors except for the ones that are several (hundred) thousand ohms. I have a 120v - 12v step down AC/DC transformer that I have used for electrolysis in the past. I appreciate your offer to help although I doubt I will be doing the procedure within the next couple of days.

I have always found sublimation/condensation very quick and easy compared to distillation of anything. Maybe that's why I find I2 the easiest. Well, technically, IMO dry Cl2 is easiest minus the storage issues.

I wonder if anyone has successfully and safetly stored compressed (l)Cl2 at home. I'm sure if it were completely dry it would be virtually unreactive towards stainless steel and possibly plain Jane carbon steel. But, that's OT.

Thanks again, Woelen.

crazyboy - 13-4-2008 at 17:06

How would you suggest making bromine from just sulfuric acid and sodium bromine?

Jdurg - 13-4-2008 at 19:05

If you purchase bromine from a chemical supplier you'll receive it in a package that is good enough for short term storage, but not for long term storage. The reasoning behind this is that the chemical supplier expects you to use it pretty quickly so the long term storage isn't a concern of theirs. If you've ever been in a chemical supply room, you'll notice that any bromine that may be in there is typically stored in a cabinet that is fairly corroded and oxidized.

As already alluded to earlier in this thread, bromine will slowly leach into glass and plastics and eat it's way out of most substances. After a long period of time, it will make some glasses brittle and weak. I initially bought my bromine (about 10 mL) from a chemical supply house. The packaging it was in allowed it to arrive safely, but it quickly ate through the bottle and started corroding the metal can it was in. I then had it sealed in a glass ampoule, but after about a year or so it made the glass VERY brittle and started leaching through. (When it was reampouled, I just had to tap the glass and it shattered). I then had it reampouled in some thicker glass and sealed in a thick acrylic resin block along with my other halogens. (This gives me a nice display of chlorine, bromine, and iodine along with a fluoride salt in glass ampoules in one resin block).

MagicJigPipe - 13-4-2008 at 19:29

Quote:

How would you suggest making bromine from just sulfuric acid and sodium bromine?


I've done it before but contrary to "theory" more HBr is produced than actual Br2. I suppose the idea is to use H2O2 as well.

crazyboy - 13-4-2008 at 20:36

Quote:

I've done it before but contrary to "theory" more HBr is produced than actual Br2. I suppose the idea is to use H2O2 as well.


Damn I tried it on a small scale and lots of red gas was evident but not enough to condense so if I add some 35% H2O2 I will get more bromine and less HBr? How much hydrogen peroxide?

12AX7 - 13-4-2008 at 21:32

Uh...maybe....stoichiometric?!

Tim

MagicJigPipe - 13-4-2008 at 23:42

Yeah, just like Tim said. A little more won't hurt and will probably increase yields. Too much and a lot of your Br2 will be dissolved in the water.

woelen - 14-4-2008 at 02:47

One word of warning. Mixing concentrated H2SO4 and 35% H2O2 is EXTREMELY dangerous. Ever heard of piranha's solution? Do a google search about this, before you proceed!

If you really want to use H2SO4 and NaBr, then you should add some water to your acid, before adding the H2O2.

MagicJigPipe - 14-4-2008 at 09:02

Yes, just stay far away from any organic materials and especially solvents.

Armistice19 - 14-4-2008 at 12:16

Over the counter dichromate can be bought easily at photography supply stores. Just google map your area for "photo supply". The products that contain potassium dichromate include any "reversal bleaches" for black and white film. Usually the color reversal bleach is just strong bases mixed with sulfites, but all of the black and white reversal bleaches contain sulfuric acid and potassium dichromate. Here is a list of reversal bleaches that are found in photo supply shops, almost all of these contain potassium dichromate. The website has supplied a material data sheet for each product. Most all of these "reversal bleaches" contain the needed chemical.

Armistice19 - 14-4-2008 at 12:18

http://siri.org/msds/gn.cgi?query=reversal+bleach&whole=...

crazyboy - 14-4-2008 at 14:32

Quote:
Originally posted by 12AX7
Uh...maybe....stoichiometric?!

Tim


Sorry I didn't know if an excess might be required.

MagicJigPipe - 14-4-2008 at 14:59

Thanks, Armistace but unfortunatly there are only a few photographic supply stores with actual storefronts and they just sell the most generic and least hazardous stuff you could even imagine. For example, they won't even sell 100% Acetic Acid. It's 28%.

Once I called every single place under "photography, supplies" and not one was willing to help me (aside from recommending the "chain" store) get GAA. Something tells me I'll find it hard to obtain dichromate OTC.

Never fear, though. I am going to order some dichromate when the time comes.

Does anyone want to help me buy some? If so, buy some anhydrous EtOH denatured with 1% isopropanol and 1% isopropyl acetate, toluene or ethyl acetate from me.

EtOH is $4 a liter. Toluene is $4 a liter. Ethyl acetate is $6 a liter. All plus shipping and all technical grade. I can also get just about any COMMON (as in, no chlorinated, no acetonitrile, no benzene etc...) solvent really cheap...

Jor - 22-5-2008 at 07:52

Well I have just made bromine again. I made a mixture of 6 grams KBr and 1.7 grams of KBrO3. Then I added 12mL 4M sulphuric acid in one portion. After shaking, everything went very red, and I saw many dark red droplets. I shaked, but for some reason, the last gram of the mixture just wouldnt turn into bromine, even after adding another 3mL of 4M sulphuric? Why is this happening?

Second, Is it possible that i cant smell bromine anymore? I smelled it during the entire, same procedure, yesterday. Today I smelled it when starting the synthesis, but during it, I smelled no bromine, but I had a continueous irritation in the nose. I was in bromine territory for max. 10 minutes, and it wasnt even very irritating, just irritating? Is this still dangerous? My yields suck, I have wasted 5 grams of KBrO3 now, and only 2mL bromine.

Oh and also, I store my bromine in a 50mL SCHOTT DURAN bottle, wich has a PTFE-lined cap. Info page:
http://www.chemie.de/products/e/64556/
As the page states, it's indeed leak proof. Buttt, the originally grey PTFE, has turned a little bit orange now. Is this of real concern?

[Edited on 22-5-2008 by Jor]

woelen - 22-5-2008 at 11:19

Bromine indeed deadens the sense of smell somewhat, but the irritation remains. It is not like H2S, which deadens the smell and removes all warning signals.
You, however, went too far. You have overirritated your nose and next time you should be somewhat more careful. I also once had this, and after a few hours I noticed that I had irritated my nose too much. I felt a certain burning sensation at my nostrils.

If you have the burning feeling of bromine, then you could inhale (CAREFULLY) some ammonia. Just waft some ammonia to your face from a 5% household bottle. This neutralizes the bromine and makes the irritation much weaker. Of course you should not get too much ammonia, because then that will cause severe irritation.

It is important that the chemicals are crunched and made into a fine powder, some insoluble crud will remain, but if the chems are finely divided, then this crud is not unused KBrO3, but KHSO4 and/or K2SO4.

Personally I find that better yields are obtained if this reaction is scaled up somewhat and you start with dissolved KBr/H2SO4 and remove the crystals of KHSO4. In practice, if you don't want to distill all of it, then a yield of 75% is feasible.

[Edited on 22-5-08 by woelen]

electrolysis

nodrog19 - 29-5-2008 at 18:49

i have tried electrolosis of NaBr and got some red liquid, but it wont dry w/ 93.2% H2SO4. that is the strongest i can get.

woelen - 29-5-2008 at 22:23

Please read this thread and the links on it carefully. What you did is making bromine-water, nothing more. Pure bromine requres a little more work ;). See all the info above.

Drying the bromine can be done with 93.2% H2SO4, but you first need to isolate bromine!

nodrog19 - 2-6-2008 at 18:10

do you mean distilling it?
what about fractional freezing?

MagicJigPipe - 2-6-2008 at 18:21

You might as well just abandon the idea of obtaining pure Br2 from dilute bromine water. Is it possible? Yes. Is it worth it? No. I have tried it before. Just stop and do it the "right" way.

Good luck.

Also, bromine dissolves in water to produce HBrO and HBr just like chlorine (HClO and HCl). That's another "problem" with Br2 water.

EDIT
I've often wondered. Would neutralization of bromine water produce some bromate? If so, would it be practical? (it need not be pure).

[Edited on 6-2-2008 by MagicJigPipe]

woelen - 2-6-2008 at 22:58

Indeed, getting bromine from dilute bromine water is hardly practical. It is done on an industrial scale, but at a small scale at home it is not worth the effort. You need to make thing so concentrated that bromine drops out of the liquid. In that way you already have 70% or so. The last amount can be isolated by distillation, but then you already have the highly concentrated stuff.

@MJP: Neutralizing bromine with warm NaOH indeed produces bromate, but only one of 6 anions is bromate:

3Br2 + 6OH(-) --> 5Br(-) + BrO3(-) + 3H2O