Bromine, in the form of HOBr, is sometimes added to pools in place of chlorine (in the form of HOCl). HOCl and HOBr are effective antiobacterial agents. At high temperatures, HOBr and HOCl can be removed from pool water due to the following reactions:
HOCl (aq) + HCl (aq) –> H2O (g) + Cl2 (g)
HOBr (aq) + HBr (aq) –> H2O (g) + Br2 (g)
Cl2 (g) escapes at lower temperatures than Br2 (g). For this reason, HOBr is occasionally used in place of HOCl in pool water that will be exposed to higher temperatures (like hot tubs and pools used outdoors in the summertime).