Bromine

Bromine, Br, is a red volatile liquid at room temperature, having a red brown vapour and a member of Group VIIb (i.e. the Halogen Group of elements) of the periodic table. It forms compounds in which its oxidation states is 1, 3, 5, or 7.
The liquid is corrosive and harmful to human tissue and bromine vapour irritates the eyes and throat.

Discovery

Bromine was discovered by A J Balardin 1826AD, by the action of Chlorine on the residues (i.e. Bromide salts) after the crystallisation of the salt from the salt-marshes of Montpellier.


		NaBr    +    Cl2    ==>    NaCl    +   Br2	

Balard also demonstrated that the liquid was an element and he suggested the name Bromine (Greek, stench) for the liquid.


Occurrence


Extraction

Bromine occurs primarily as bromide salts (e.g. Sodium Bromide, NaBr) in sea-water. On passing a stream of chlorine gas through a solution containing Bromide Ions, Br(-), free elemental bromine is released.


	2 Br(-)   +   Cl2   ==>   Br2   +   2 Cl(-)


Preparation

Bromine can be prepared in the laboratory by heating Potassium Bromide, KBr, with dilute Sulphuric Acid, H2SO4, and Manganese Dioxide, MnO2.


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


Manufacture

Bromine is manufactured industrially by allowing a solution of Potassium Bromide to flow down a tower, against a stream of Chlorine gas rising up through the tower.


	     2 KBr   +    Cl2    ==>    Br2   +    2 KCl	


Properties


Reactions


Uses

Bromine is used in a vide range of industries :

Detection and Analysis

Bromine is detected by the brown colour of its vapour, and by its action on Iodide salts, (e.g. Sodium Iodide, NaI), which are oxidises to free elemental Iodine.


		2 NaI    +    Br2    ==>   2 NaBr    +     I2	

The Iodine liberated in this reaction turns starch indicator solution to a blue colour.


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