Athiril
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Ways to Bromine (or HBr) from KBr
Saw you can produce iodine from iodide salts with sulphuric acid, or sulphuric acid catalyst in potassium permanganate.
I have potassium permanganate, but no sulphuric acid. I have glacial acetic acid, ca get sodium bisulphate easily at the shop etc.
And have metabisulphite, so I could produce some weak sulphuric acid for a catalyst.
What I want to do, is produce a small amount of gas/fumes of bromine, or HBR gas in an enclosed tank to let some photographic film sit in the fumes
for an experiment (also Iodine fumes, or HI gas at a later stage for a different experiment).
For the current experiment, it can't be iodine or HI, as AgI isn't really developable, so I need it to be bromide based. Although chlorine is another
option.
Which I could just put in some 30% HCl and let it fume.
Since I only need to make a small amount to envelop the film in, in an enclosed space (for the film), was wondering if anyone had some suggestions.
Also saw alcohols + bisulphate would form sulphuric acid, that seems pretty easy, unless the alcohol/ketones/etc would interfere with the reaction
with the halides, that'd be fine and I wouldn't need to treat that any further.
[Edited on 12-6-2011 by Athiril]
[Edited on 12-6-2011 by Athiril]
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#maverick#
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look for h2so4 as drain opener menards has the good kind rooto if ur in us
http://www.youtube.com/watch?v=OB4MmPTOBxg&annotation_id...
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not_important
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A bromide salt, MnO2, and a storng mineral acid =- H2SO4 is best but HCl works if there's a lot of excess bromide to mop up any Cl2 formed.
You need a fairly concentrated solution, Br2 is slightly soluble in water so dilute solutions don't release much Br2. A bisulfate might replace the
H2SO4, I've never tried it. You could try warming a moist paste of NaBr, MnO2, and NaHSO4 to see if it releases Br2 - do it on a real small scale
just as a test, then if it works revise as needed to the amount you need.
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sternman318
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Hydrogen peroxide and acid worked very well for me, and doesnt leave you with a mess of MnO2 ( if you used permanganate) or Mn+2 ( if you used MnO2).
I ended up using 3% hydrogen peroxide that was concentrated by freezing it and pouring off the unfrozen stuff and 1.0 M sulfuric acid. I would use
more concentrated acid if possible, and I suspect any acid would work instead. The only issue is you produce bromine water... which isn't a biggie
because heating it releases Br2 vapors.
[Edited on 12-6-2011 by sternman318]
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Athiril
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I don't have H2SO4, getting it may take some time, and I'm ready to trial a first run on this film. Searched second largest bunnings up and down for
it, looked at the label on everything, couldn't find zip.
I don't think any acid will work, it has to be more electronegative than bromine iirc. For example, I've tried citric acid + KMnO4 + KBr, colour
change, but thats it as far as I could tell.
I'd prefer HBr, but Bromine fumes would be fine as long as it doesn't condense on the film.
The video gives me an idea, free chlorine will displace bromine from halide salts.
Perhaps trichloroisocyanuric acid + KMnO4 might work for me in that sense to kick out some chlorine which will kick out the bromine.
Or trichloroisocyanuric acid and sodium hypochlorite both of which are in the supermarket.
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LanthanumK
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Do you have concentrated phosphoric acid? It reacts with a bromide to make hydrogen bromide gas.
hibernating...
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Athiril
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No, but I saw some laying around where I used to live, damn, will have to get some.
And good news every one. I went hunting through a random large box of photo chemicals I got from vanbar looking for any strong acids used to
store/preserve other chemicals inside them.
One small bottle of sulphuric acid and sodium molybdate solution, and one black bottle with a crusty old paper label that barely is legible, that
reads sulphuric acid.
test confirms it's sulphuric acid, not sure of the strength, I doubt it'd be concentrated much, though it's enough for my purposes.
[Edited on 12-6-2011 by Athiril]
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ItalianChemist
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very simple! Add conc. sulfuric acid to a solution of KBr, in an ice bath...then add very slowly 35% H2O2 and distill the bromine!
[Edited on 12-6-2011 by ItalianChemist]
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sternman318
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You should be able to use hydrochloric acid and hydrogen peroxide, I BELIEVE I also tried that. In that case, you will get some chlorine gas I assume,
but as you said, the chlorine will oxidize the bromide ions
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Athiril
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Okay the chlorine reaction is taking place, but the bromine doesn't seem to be (H2SO4 with KMnO4 and KBr, vs NaCl).
Or maybe its taking it's sweet time. Or the acid may be far too dilute.. in which case I could add NaCl to get Cl2 to kick out Br2.. though I'd
probably get Cl2 gas as well not just Bromine, so I'd get an uneven mix of silver bromide and silver chloride on the emulsion.. which eventually
would all be silver chloride anyway if left to completion.
Don't have any H2O2 atm, only can get 3% from the shop, would have to wait on stronger stuff (50%).
Might go for chlorine then, silver chloride should be fine for a first test run.
10 mL weighed approximately 11.62g, so given my calculations there should be approx 19% by volume H2SO4, or approx 0.355g of H2SO4 per 1 mL.
[Edited on 12-6-2011 by Athiril]
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sternman318
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Search the forms for concentrating hydrogen peroxide by freezing. I think you get around 20%- whatever it is, it was strong enough to turn my skin
white and leave an uncomfortable burn. So if your current method does not yield good results, try using excess h2o2
Edit : http://www.sciencemadness.org/talk/viewthread.php?tid=10113#...
[Edited on 12-6-2011 by sternman318]
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Athiril
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When I opened the tank this morning, film appears to be bleached, and liquid in the bottom of the tank was yellow, since I opened it to light for
inspection, needs another bleach, I mixed more up, and it yellowed straight away this time and started to smell (sulphuric acid, then added KMnO4,
then clumps of KBr and mixed, last time I dissoled KBr into the acid then added KMnO4), so quickly put it in the tank.
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Fleaker
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The absolute best way to make bromine (if you have the reagents) is from potassium bromide, potassium bromate, and sulfuric acid. It's nigh on
quantitative and doesn't produce any BrCl contamination nor is the bromine very wet like if one uses Caro's acid.
Neither flask nor beaker.
"Kid, you don't even know just what you don't know. "
--The Dark Lord Sauron
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woelen
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In your case the simplest thing to do is buy some sodium bisulfate pH minus from the hardware store. Mix this with KBr and KMnO4 and add a few drops
of water, such that it becomes a slurry. In this way you get quite a lot of bromine vapor.
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Athiril
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When I opened it this morning, the spacer reels were yellowed, and the film was uneven (bleached properly, but looks like it has bromine on it in
places) which will affect pictures, so I need to switch to chlorine gas and just use that, or HBr gas I think.
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DJF90
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Fleaker: Are you suggesting mixing the bromide and bromate together and then dripping in conc. H2SO4 or are you implying the use of solutions? I'd
appreciate it if you could provide a reference with experimental section.
[Edited on 13-6-2011 by DJF90]
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woelen
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I used the mixing of bromide and bromate for making pure bromine. The following works very well:
Dissolve 100 grams of KBr in 200 ml of water. This takes a lot of time as the solution cools down considerably while doing so.
Pour in 60 ml of concentrated sulphuric acid in this solution. It will become hot and somewhat orange (already some bromine is formed, which remains
in solution). Add the acid very slowly and stir well. Be careful: A LOT of heat is produced, allow the liquid to cool down between additions of small
amounts of acid.
Let the solution stand. Lots of crystals of (impure) KHSO4 are formed and these settle at the bottom.
Decant the liquid from the crystals. Try to obtain as much as possible of the liquid. This is what contains the bromide.
Take 30 grams of KBrO3 and crunch the crystals, such that a fine powder is obtained.
Carefully, in steps of 1 gram, add the KBrO3 to the liquid and stir. LOTS of bromine are formed and copious amounts of red fumes appear. Do the
addition into a bottle which can be capped, otherwise you loose a lot of bromine vapor.
After addition of all the KBrO3 a thick layer of liquid bromine will be present at the bottom. The total amount will be well over 20 ml (appr. 65
grams). The rest of the bromine remains dissolved in the liquid.
With a pasteur pipette you can remove the Br2 from the lower layer. In this way you recover approximately 75% of all bromine. If you want the other
25%, then you need to distill.
Shake the 20 ml of bromine with 10 ml of concentrated sulphuric acid to get rid of adhering and dissolved water. Store the bromine under this 10 ml of
acid. It remains dry in this way and pure.
A similar thing I have done with NaBr and KBrO3. In that case you need slightly different ratios of chemicals, but the idea is the same. I used
distillation in order to get all of the bromine.
http://woelen.homescience.net/science/chem/exps/raw_material...
[Edited on 13-6-11 by woelen]
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