source :

 Methods of preparation :

1.  By passing chlorine gas in aqueous solution of KBr or MgCl2 :

2KBr +Cl2  ———->   2KCl + Br2

MgBr2 + Cl2 ———> MgCl2 + Br2

2. By the reaction of HCl with a mixture of KBr(potassium bromide) and KBrO3(potassium bromate) :

5KBr + KBrO3 +6HCl ———> 6 KCl + 3Br2 + 3H2O

3. By heating KBr or NaBr, MnO2 with concentrated H2SO4:

2KBr + MnO2 + 3H2SO4 ———>  Br2 + 2KHSO4 +MnSO4 +2H2O


2NaBr + MnO2 + 3H2SO4 ———>  Br2 +2 NaHSO4 +MnSO4 +2H2O

Manufacture from Carnallite:

Carnallite is KCl.MgCl2.6H2O. Carnallite obtained from Stassfurt in Germany  also contains MgBr2. Carnallite contains about 0.25% Br2  in the form of MgBr2. On concentrating the aqueous solution of carnallite , crystals of KCl separate out. The filterate contains MgCl2 and MgBr2. This  filterate is also called  mother liquor.

Hot mother liquor is sprayed from the top of tower which is packed with stone pieces. A mixture of chlorine gas and stream is passed from the bottom of the tower. Bromine is liberated from MgBr2 which is  present in the mother liquor.

MgBr2 + Cl2   ———-> MgCl2 +Br2

Vapours of bromine are drawn off from the exist and condensed. Vapours  which is not get condensed ,are taken into a chamber containing iron then it  reacts with iron and form ferrous bromide and ferric bromide. This mixture is used for the manufacture of KBr.

3Fe + 4Br2 ——-> FeBr2 + 2FeBr3

when mother liquor is sprayed from the top, some liberated bromine dissolves in it and comes in recovery chamber. Bromine collected in recovery chamber is vaporized by steam. The vapours of bromine are  passed through the tower again and drawn off from the exist at the top of the tower and condensed.

Manufacture  of bromine  from sea water :


source :

Sea water contains  KBr , MgBr2  &  NaCl. Sea water is concentrated and made acidic and then Cl2 is passed in it.

MgBr2 +Cl2  ———> MgCl2 +Br2

2KBr + Cl2 ——-> 2KCl + Br2

Bromine  dissolves  in hot water. Hot air is passed in water to vaporize Br2. These  vapours are passed in hot aqueous solution of sodium carbonate. A mixture of NaBr & NaBrO3  is obtained in solution.

Na2CO3 + Br2 ——-> NaBr +  NaBrO3 +CO2

Solution containing NaBr and NaBr03 is treated with concentrated H2SO4 then bromine is obtained which is condensed and collected.

5NaBr +NaBrO3 +6H2SO4 ——–> 6NaHSO4 + 3Br2 +3 H2O.