Bleaching powder manufacturing process, uses, reactions

Bleacing powder is calcium hypochlorite ( Ca(OCl)2 ). It is a one of the major chemical industry in the world. Limestone and chlorine gas are used as raw materials to manufacture bleaching powder which is used as a disinfectant and as an oxidizing agent. Bleaching powder show different reactions.



In this tutorial, we study about followings.

  1. What is bleaching powder?
  2. Manufacturing process
  3. Uses of bleaching powder
  4. Reactions of bleaching powder


What is bleaching powder

Bleaching powder is a white - yellowish powder which very well dissolves in water. The active ingredient of bleaching powder is calcium hypochlorite ( Ca(OCl)2 ). It is an inorganic compound.


Bleaching powder composition

Bleaching Powder chemical composition: Ca(ClO)2CaCl2Ca(OH)2.2H2O


Calcium hypochlorite - Ca(OCl)2

Ca(OCl)2 is a white, corrosive solid that comes either in tablet form or as a granular powder in the market. It easily emits chlorine gas easily when it contacts with water or moisture.



Raw Materials of bleaching powder manufacturing process

  • Limestone (CaCO3) - to obtain calcium oxide
  • Chlorine gas (Cl2)


Bleaching powder manufacturing process

Steps, reactions, materials of bleaching powder and physical conditionsin manufacturing process is explained below.


Heating limestone

First, slaked lime (CaO) is produced by heating limestine. As a by product carbon dioxide is given.

calcium-carbonate-decomposition

Calcium oxide and water reaction

Calcium oxide is mixed with water to take calcium hydroxide ( Ca(OH)2 ). Ca(OH)2 is precipitated in concentrated solutions.


CaO + H2O slaked lime

Calcium hydroxide and chlorine gas rection

  • Finally, Calcium hydroxide ( Ca(OH)(s) ) is reacted with chlorine ( Cl2 ) gas. This reaction gives the bleaching powder.
    slaked lime and chlorine gas reaction


    • Bleaching powder manufacturing process in industrial plant

    bleaching powder manufacturing process

    Bleaching process of bleaching powder

    Reason to bleaching property is hypochlorite ion (OCl-). Colourful things are oxidized by atomic oxygen ('O') which is formed by OCl- ion. Atomic oxygen is very reactive.

    bleaching process of bleaching powder

    when atomic oxygen is reduced, Colorful things are oxidized simultaneously.


    Fe2+, I-, Br- ions can be oxidized by bleaching powder.


    Uses of bleaching powder

    • As a bleach.
    • As a disinfectant. As an example, in water treatement processes.
    • To manufacture chloroform


    Explain uses of bleaching powder in detail


    Purifying water using bleaching powder in purification plants

    A suspension of bleaching powder in water is added dropwise to water and stirred. In earlier times, chlorine gas (Cl2) was used. But due to inconvenience of transporting heavy gas cylinders of chlorine, this method is abandoned.


    Reactions of bleaching powder


    Dilute acids and bleaching powder reaction

    When bleaching powder is heated with a dilute acid, chlorine gas is emitted.


    Reaction of air and bleaching powder

    Gaseous CO2 dissolve well in the water. That forms carbonic (H2CO2) acid. Carbonic acid can release Cl2 from bleaching powder.



    Bleaching powder and water reaction

    Bleaching powder hydrolysis to hypochlorous acid ( HOCl ) and calcium hydroxide ( Ca(OH)2 ). Hypochlorous acid is not stable and again hydrolysis to chlorine gas.



    Oxidation characteristic of bleaching powder

    Bleaching powder can oxidize another substances. Therefore bleaching powder can behave as an oxidizing agent.


    Acidic KI and bleaching powder reaction

    Add bleaching powder to acidic KI solution. Purple colour I2 is emitted. When I2 contact with farina, you can see purple colour.

    KI and bleaching powser reaction

    Acidic Fe2+ solution and bleaching powder reaction

    Ferrous ions ( Fe2+ ) are oxidized to ferric ( Fe3+ ) ions. You can identify Fe3+ ions by adding KSCN. Then red colour [Fe(SCN)]2+ is given.

    ferrous ion and bleaching powder reaction

    What is the commercial bleaching powder mixture?

    Ca(ClO)2CaCl2Ca(OH)2.2H2O



    Does ammonia react with bleaching powder?

    Bleaching powder reacts with ammonia and give calcium chloride ( CaCl2 ), nitrogen gas (N2 ) and water as the products.




    What are the other disinfectants can be used insted of Ca(OCl)2

    Sodium hypochlorite (NaClO) can be used as a disinfectant. But HOCl is more efficient than NaClO and Ca(OCl)2 in disinfecting process.

    Bleaching process of HOCl

    HOCl decomposes to HCl, atomic oxygen atom and water. Atomic oxygen is very reactive and is reduced to O2- readily. With that step, coloured thing is oxidized to get colourless.



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