HBrO3 is surprisingly stable, as long as you don't get too high a concentration. I have done experiments with it, up to 10% or so, using barium
bromate and sulfuric acid. Even boiling the solution does not destroy the acid.
Barium bromate can be made quite easily. It is not very soluble in the cold and if you have NaBrO3, then you can make it from a soluble barium salt
(e.g. BaCl2) and NaBrO3 and purify it by means of recrystallization. It can even be made from KBrO3 (which is less soluble than NaBrO3). If you want
to make a solution with HBrO3, containing only little amounts of metal ions, then you must recrystallize your barium bromate from boiling hot water.
Making pure HBrO3 solutions without barium ions or sulfate ions is quite laborious. I proceeded by first preparing an approximately 3M solution of
H2SO4. As I did not knbow precisely the concentration of my concentrated H2SO4 (could be anything between 95% and 98%) I decided to roughly make 3M
solution and then titrate against NaOH. I have 99+% pure NaOH and very quickly weighed this as it absorbs moisture from air quickly and made a
solution of known concentration with this. I think that I could achieve appr. 1% accuracy with this.
Weighing Ba(BrO3)2 is accurate, once you have a nice dry product. IIRC it exists as the monohydrate, when crystallized from water. I mixed solutions
of acid and a hot solution of barium bromate. I decided to take 1% extra of the acid, preferring a little sulfate as impurity over a little barium as
impurity. Getting it exactly matching is cumbersome and requires frequent probing. I did not take the effort to do that.
The biggest practical problem I ran into was that on mixing solutions of barium bromate and sulfuric acid, you get a lot of very fine white
precipitate, which is not easy to filter. Using paper is not advisable because the strongly acidic and oxidizing solution destroys the filter paper
quickly. I decided to boil the solutioin for a while to make the precipitate somewhat more compact and easier to settle and then allowed the
precipitate to settle. But settling took a long time and it did not really settle at the bottom. A tick white layer remained. I accepted the loss and
pipetted the liquid above the white precipitate.
After all this labor I finally had a solution of HBrO3, with a slight impurity of H2SO4.
I used my solution for oxidation experiments, but you could use that for making Sr(BrO3)2, by adding Sr(OH)2 or SrCO3 to the acid. Any cloudiness can
be allowed to settle (that will be SrSO4) and removed, the Sr(BrO3)2 will remain in solution, if it indeed is soluble at 300 grams per liter.
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