Bleaching Powder, also called Calcium Hypochlorite or Calcium Oxychloride, is a chemical compound which is used for various purposes. It has various uses but it is majorly used for its bleaching action, the bleaching action of Bleaching Powder is used to bleach clothes in laundries, and others. Bleaching powder is also used for various aspects such as disinfectants, cleaning potable water and others. In this article, we will read about Bleaching Powder, its properties, and others in detail.
Bleaching Powder
Bleaching Powder, also known as chloride of lime, is solid in texture and yellowish-white in colour. Bleaching powder can be recognised by the smell of chlorine. Bleaching powder is generally used for the removal of colour, as indicated by its name. It is also known as a bleaching agent.
The image given below shows the bleaching powder.
Bleaching powder, when dissolved in water, forms an aqueous solution, which is basic in nature. Bleaching powder works on the principle of oxidation. The bleaching action of the bleaching powder is caused due to the presence of chlorine in it. A compound of calcium hydroxide exists, which is known as slaked lime reacts to form bleaching powder.
Slaked Lime reacts with the chemical compound chlorine, it gives a compound, bleaching powder (calcium oxychloride) and gives water as a by-product. Bleaching powder is an inorganic compound with the formula Ca(OCl)2. The compound is soluble in water but due to the presence of impurities, the solution obtained by mixing this compound in water is not a clear solution.
Chemical Name of Bleaching Powder: Calcium Hypochlorite
Chemical Formula of Bleaching Powder: CaOCl2
Structure of Bleaching Powder
The structural formula of bleaching powder contains two atoms of chlorine. Among these two atoms, one of them is properly bonded to the atoms of the chemical compound Calcium. The other atom of Chlorine results in the formation of a bond with the atom of Oxygen.
The image given below shows the structure of Bleaching Powder.
Preparation of Bleaching Powder
The manufacture of bleaching powder is carried out in Bachmann's plant as follows,
The entire system is prepared for the manufacturing of bleaching powder, containing a vertical cast-iron tower packed with a hopper at the top, two inlets near the base (one for chlorine and the other for hot air) and an exit for waste gases near the top. This tower is then fitted with shelves that are placed at varying heights with rotating rakes. The shelves are a total of eight in number. Slaked lime is introduced into the hopper. It eventually comes in contact with chlorine moving slowly in the upward direction. The bleaching powder is then collected at the base in the barrel area of the tower. The reaction used in the above reaction is, Slaked lime + Chlorine ⇢ Bleaching powder + Water
Ca(OH)2 (aq) + Cl2(aq) ⇢ CaOCl2(aq) + H2O(l)
Important conditions to be maintained for preparation of the Bleaching Order
- Chlorine used should be diluted in nature.
- Temperature should be maintained below 40°C.
Properties of Bleaching Powder
Properties of Bleaching Powder can be studied under two heading which includes,
- Physical Properties of Bleaching Powder
- Chemical Properties of Bleaching Powder
Physical Properties of Bleaching Powder
Bleaching Powder is a pale yellowish powder that possesses a strong smell of chlorine. Its physical properties include,
- It performs a reaction with dilute acids to produce chlorine.
- It is soluble in cold water. The lime is left as an insoluble residue on dilution.
- In reaction with an excess of a dilute, for instance, dilute sulphuric acid, the chlorine from the bleaching powder gets liberated.
Thereby, the chlorine that is produced as a result of the action of dilute acid on bleaching powder acts as a bleaching agent. Therefore, chlorine is the bleaching agent in bleaching powder.
Chemical Properties of Bleaching Powder
Various Chemical Properties of Bleaching Powder include,
- Bleaching powder reacts with dilute sulphuric acid, to form calcium sulphate and chlorine gas, water is also produced in the reaction.
CaOCl2 + H2SO4 - → CaSO4 + Cl2 + H2O
- Bleaching powder reacts with CO2 to produce chlorine gas and calcium carbonate.
CaOCl2 + CO2 → CaCO3 + Cl2
- Bleaching powder reacts with dilute hydrochloric acid (HCl), to produce chlorine gas.
CaOCl2 + 2HCl → CaCl2 + Cl2 + H2O
The chlorine released in various reactions of bleaching power releases chlorine gas which is used as a bleaching reagent.
pH of Bleaching Powder
Bleaching Powder is basic in nature and the bleaching powder which is generally used for domestic purposes has a pH value of 11. Thus, bleaching powder has an irritating nature when coming in contact with human skin.
Concentrated Bleaching Powder, which has a high concentration (10-15% ) of sodium hypochlorite, has a pH value of 13. Thus, it is highly alkaline in nature.
Uses of Bleaching Powder
Bleaching Powder has the following uses:
- Used as an oxidising agent in chemical industries.
- Used for disinfection of drinking water.
- Used for bleaching washed clothes in the laundry.
- Used for bleaching wood pulp in the paper manufacturing industry.
- Used as a bleaching agent in the textile industry for bleaching cotton and linen.
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