woelen - 27-3-2006 at 03:54
I have a lot of NaHSO4 and also a lot of both KBr and NaBr. I would really like to have some aqueous HBr and use these chemicals for that.
Has anyone of you experience with making HBr from these chemicals? I myself tried heating NaHSO4 in a test tube, until it melts and subsequent boiling
away of water is completed. Then I added some solid NaBr. It started bubbling vigorously, but unfortunately, the gas coming off is light brown/orange.
This is an indication that the reaction is not very clean and some of the NaBr is oxidized to Br2 and the NaHSO4 reduced to SO2. I collected this gas
into some water and prepared a small amount of very dilute HBr. However, this liquid contains quite some H2SO4 as well. The SO2 and Br2 which pass
into the liquid react with each other in the water again to HBr and H2SO4. This really sucks....
Does any one of you know of a method of obtaining pure HBr, without Br2, SO2 or H2SO4 from NaHSO4 and NaBr (or KBr). I thought the formation of Br2
only is a problem with concentrated H2SO4, but it apparently also is with NaHSO4 
.
If I have such a synth, then I have a very good use for all my NaHSO4 and NaBr.
solo - 27-3-2006 at 06:05
Something I read on the Hive archives , where they produce the Br2 and then HBr using the material you have on hand........solo
Note: cut and paste on your address window the whole thing.....
http://72.14.203.104/search?q=cache:WZz6pMFHCPEJ:12.162.180.114:90/synthetika/hiveboard/chemistrydiscourse/000508433.html+synthesis+of+HBr+from+NaBr/K
Br&hl=en&lr=&client=safari&strip=1
[Edited on 27-3-2006 by solo]
neutrino - 27-3-2006 at 07:04
HBr was only discussed as a starting material and impurity in the final product (Br<sub>2</sub>
. There wasn’t much there that would be of use for making HBr.
Reading through the thread, I noticed that one person stored his bromine dissolved in hexane. Isn’t that a bad idea? I would think that free radical
bromination would occur, leading to some problems...
solo - 27-3-2006 at 07:52
When all else fails go to the books..............solo
H2SO4+ KBr-----------> HBr + KHSO4
A mixture of 120g of potassium bromide and 200ml of
water cooled in ice while 90ml of concentrated sulfuric
acid is slowly added, The temperature must not rise over
75°C during this addition; otherwise roe bromine may be
formed, causing a loss in yield. The reaction mixture is
cooled to reom temperature and the potassitun bisulfate is
filtered off by sucten through a fritted funnel or a hardened
filter paper. The filtrate is then fractionated and the mate-
rial boiling from 122-127C is collected as constant-boiling acid.
Yield : 85%
In all eases where a mixture of sulfuric and .b,ydrobromic
acids is obtained, a redistiIlation is necessary to remove
ut 0.01% of sulfate in the first fractionation; only the
acid with a steady buffing point is retained. This operation
entails a toss of about 15% in yield,
............source, Inorganic Preparations, Schessinger, 1962, Pg 146
chromium - 27-3-2006 at 08:31
Maybe to use aqueous solution instead of fused NaHSO4 and then distill solution? This surely will give some HBr (i suppose that decomposition will not
take place then) but yield may be low.
guy - 27-3-2006 at 14:34
An aqueous solution of NaHSO4 is not strong enough to cause any considerable yield of HBr. If HBr decomposes that easily, then I don't think this
method can produce good amounts of HBr.
And will this reaction cause HCl to decompose if NaBr is replaced with NaCl?