Making an ampoule with non-wetting bromine takes patience, but is not really difficult. Mix your bromine with conc. H2SO4 and shake it well. Next,
distill the bromine from the H2SO4 in well dried and clean glassware (I rinse my glassware with a little pure acetone and then with quite a lot of
distilled water and let it dry for a few days in a warm place before I use it for such critical distillations). Just distill all bromine until just a
few small droplets of bromine are visible in the H2SO4, then immediately stop the distillation. You don't want the last part, which may contain higher
boiling impurities.
The dried bromine then must be ampouled. Even that bromine still wets the glass, but over time (a few weeks), the wetting becomes less prominent and
after a month or so, it hardly wets the glass. Bromine slowly becomes more dry, when in the ampoule. If you have a very small amount of water to start
with (hence the drying before ampouling), then the last amount of water is destroyed slowly in the ampoule by the following reaction:
Br2 + H2O <----> HBr + HOBr
2 HOBr ---> 2 HBr + O2
So, pressure will rise a little inside the ampoule, but you do not need to worry about cracks, even with imperfectly dried bromine, because the amount
of water is very small anyway (a very very small amount of water makes the bromine wetting the glass).
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