How do I generate anhydrous HBr gas?
bbsm...@elf.fidobbs.com
Anyone know a simple way to generate anhydrous
HBr gas?
Someone suggested phosphoric acid + KBr. I
tried it, and it doesn't seem to work.
I am not interested in reacting elemental
Bromine with hydrogen :-)
Thanks.
Alan Beckman
A classic way is by dropping sulfuric acid on to sodium, or potasium
bromide. Old chemistry texts show examples and simple drawings of
apparatus to use.
James Deline
bbsm...@elf.fidobbs.com wrote:
: Anyone know a simple way to generate anhydrous
: HBr gas?
: Someone suggested phosphoric acid + KBr. I
: tried it, and it doesn't seem to work.
Well, I know for a fact that reaction of sulfuric acid (98%) with sodium
chloride produces HCl, so I suppose that substituting with sodium or
potassium bromide would have the desired result.
Alan "Uncle Al" Schwartz
bbsm...@elf.fidobbs.com wrote:
>Anyone know a simple way to generate anhydrous
>HBr gas?
>
>Someone suggested phosphoric acid + KBr. I
>tried it, and it doesn't seem to work.
>
>Bromine with hydrogen :-)
>
>Thanks.
I generally turn the valve on the lecture bottle.
Adding solid NaBr to concentrated sulfuric acid, stirring and gently
heating if necessary suffers from the possiblity of oxidizing to
elemental Br2. It will be obvious if it happens.
Grinding equimolar amounts of NaHSO4 and NaBr and heating might be
better, using supported phosphorus pentoxide to thoroughly dry it.
--
Alan "Uncle Al" Schwartz
Uncl...@ix.netcom.com ("zero" before "@")
http://www.netprophet.co.nz/uncleal/ (naughty beyond measure;
"Quis custudiet ipsos custodes?" The Net! funny beyond endurance)
William R. Penrose
>Anyone know a simple way to generate anhydrous
>HBr gas?
>Someone suggested phosphoric acid + KBr. I
>tried it, and it doesn't seem to work.
No, but you should be able to make it by dripping conc hydrobromic acid or a
saturated solution of KBr into conc sulfuric acid. I did this once to make
dry methanolic HBr for analysis of polyethylene glycols, and it worked fine.
You can dry it a little more by bubbling it through some more conc sulfuric
downstream. (Of course, you can buy it cheaper than you can make it.)
Bill
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Laboratory
In <1996050116...@getnet.com> bbsm...@elf.fidobbs.com writes:
>
>Anyone know a simple way to generate anhydrous
>HBr gas?
>
>Someone suggested phosphoric acid + KBr. I
>tried it, and it doesn't seem to work.
>
>I am not interested in reacting elemental
>Bromine with hydrogen :-)
>
>Thanks.
>
Well, you have a few answers already. I do endorse the KBr or NaBr
plus sulfuric acid method as the easiest. Halogen salts will break
apart under highly acidic conditions. I am not sure what proportion
will turn to HBr and what will remain as Br2, you should be able to
find that in a chemistry text.
Also, alkyl halides can generate the corresponding acid halide when
reacted with certain organic compounds. I would not necessarily
recommend this because a violent (even explosive) reaction can result.
Have fun and be careful.
Romas Cesas
Rick Fletcher
William R. Penrose (wpen...@interaccess.com) wrote:
: In article <1996050116...@getnet.com> bbsm...@elf.fidobbs.com writes:
: >Anyone know a simple way to generate anhydrous
: >HBr gas?
: dry methanolic HBr for analysis of polyethylene glycols, and it worked fine.
: You can dry it a little more by bubbling it through some more conc sulfuric
: downstream. (Of course, you can buy it cheaper than you can make it.)
It works. At least we do it this way in P-Chem lab (with NaCl rather than
NaBr) to make the HCl and DCl (add D2O to the acid) we use in the classic
IR lab. This method turns out to be less expensive than purchase of the
deuterated gas and since we need to do it for the DCl, we use it to make
both in the same cell.
--
Rick
T. Rick Fletcher - http://www.chem.uidaho.edu/~fletcher/
Assistant professor of chemistry | That's Idaho, not Iowa. | ad hominem
University of Idaho | Upper Left Hand Corner. | ad hominem
Moscow, ID 83844-2343 | No, I don't grow potatoes. | ad hominem
Pere Lloveras
> tried it, and it doesn't seem to work.
>
> I am not interested in reacting elemental
> Bromine with hydrogen :-)
>
*By reacting bromine with tetraline (Weygand's Preparative Organic
Chemistry p.120)
*By reducing bromine with sulfur dioxide (Organic Synthesis, coll. vol.I)
Hope this can be helpful.
--
* Pere Lloveras
* LITRANS S.A./AMIFARMA S.A.
* Barcelona (Spain)
* E-mail: lit...@bcn.servicom.es
Dr Andras Kotschy
The traditional way of generating dry HBr is adding bromine to decaline.
For details see Vogel`s Textbook or other manuals.
----------------------------------
Dr. Andras Kotschy
kost...@gmail.com
> HBr gas?
>
> Someone suggested phosphoric acid + KBr. I
> tried it, and it doesn't seem to work.
>
> I am not interested in reacting elemental
> Bromine with hydrogen :-)
>
> Thanks.