If you add dilute (e.g. 20%) H2SO4 to either solid KBrO3 or to a solution of KBrO3, then you should not get any bromine. If your acid contains
reducing agents (e.g. organics), then you might get bromine with such dilute acid.
If you add concentrated H2SO4 to solid KBrO3, then you'll see bubbles of oxygen and fumes of Br2.
If you add concentrated H2SO4 to a solution of KBrO3, then you might get some bromine. At the place where the acid still is concentrated and where it
gets in contact with solution of KBrO3, the total acid concentration may be so high that the formed HBrO3 decomposes. For this reason, it is important
to first dilute the H2SO4 and then add this to the bromate.
As Bedlasky wrote, use pure acid, any reducing material in the acid will interfere with the BZ-reaction. |