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woelen
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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]
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MagicJigPipe
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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.
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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.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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woelen
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| 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.
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MagicJigPipe
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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.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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crazyboy
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How would you suggest making bromine from just sulfuric acid and sodium bromine?
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Jdurg
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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).
\"A real fart is beefy, has a density greater than or equal to the air surrounding it, consists of the unmistakable scent of broccoli, and usually
requires wiping afterwards.\"
http://maddox.xmission.com. |
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MagicJigPipe
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| Quote: |
How would you suggest making bromine from just sulfuric acid and sodium bromine?
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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.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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crazyboy
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| 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?
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12AX7
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Uh...maybe....stoichiometric?!
Tim
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MagicJigPipe
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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.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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woelen
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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.
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MagicJigPipe
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Yes, just stay far away from any organic materials and especially solvents.
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Armistice19
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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.
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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Armistice19
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http://siri.org/msds/gn.cgi?query=reversal+bleach&whole=...
“Imagination is more important than knowledge. For knowledge is limited to all we now know and understand, while imagination embraces the entire
world, and all there ever will be to know and understand.” -Albert Einstein
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crazyboy
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| Quote: | Originally posted by 12AX7
Uh...maybe....stoichiometric?!
Tim |
Sorry I didn't know if an excess might be required.
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MagicJigPipe
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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...
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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Jor
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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]
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woelen
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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]
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nodrog19
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electrolysis
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.
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woelen
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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!
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nodrog19
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do you mean distilling it?
what about fractional freezing?
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MagicJigPipe
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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]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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woelen
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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
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