Washing Soda is sodium carbonate containing 10 molecules of water of crystallisation. So, we can say that washing soda is sodium carbonate decahydrate (Na2CO3.10H2O).
The sodium carbonate which does not contain any water of crystallisation is called anhydrous sodium carbonate or soda ash (Na2CO3).
How Washing Soda is produced?
In the following three steps, washing soda is prepared from sodium chloride or common salt.
Firstly, a cold and concentrated sodium chloride solution is reacted with ammonia and carbon dioxide to obtain sodium hydrogen carbonate.
The sodium hydrogen carbonate is slightly soluble in water, so it precipitates out as solid.
NaCl +NH3 +CO2 +H2O → NaHCO3 +NH4Cl
Secondly, now sodium hydrogen carbonate is separated by filtration, dried and heated. On heating sodium hydrogen carbonate decomposes to form sodium carbonate. This anhydrous sodium carbonate is known as soda ash.
2NaHCO3 → Na2CO3 +H2O +CO2
The preparation of Sodium Carbonate is also known as Solvay process. But before that calcium carbonate (limestone) was heated to release carbon dioxide.
Thirdly, anhydrous sodium carbonate or soda ash is dissolved in water and recrystallised to get washing soda crystals containing 10 molecules of water of crystallisation.
Na2CO3 + 10H2O → Na2CO3.10H2O
What are the Properties of Washing Soda?
- Washing Soda is a transparent crystalline solid.
- It is one of the few metal carbonates which are soluble in water.
- Do you know that the solution of washing soda in water is alkaline which turns red litmus to blue?
- Washing Soda has detergent or cleansing properties because it can remove dirt and grease from dirty clothes. How it cleanse the clothes? Washing soda attacks dirt and grease to form water soluble products, which are then washed away on rinsing with water.
- It has a melting point of 8510C.
What are the uses of Washing Soda?
- Washing Soda is used as cleansing agent for domestic purposes like washing clothes. In fact sodium carbonate is a component of many dry soap powders.
- It is used for removing permanent hardness of water.
- It is used in the manufacture of glass, soap and paper.
- It is used in the manufacture of sodium compounds like borax.
- It is the most important agent in laundries.
- It is used in paper, textile, soap, and detergent industries.
Therefore, we can say that washing soda is sodium carbonate with 10 molecules of water which is mainly used as a cleansing agent.