The Story of Washing Soda: Na₂CO₃·10H₂O

The washing soda's chemical name is sodium carbonate. Pure sodium carbonate is a white, odourless powder that is hygroscopic means it absorbs moisture from the air.

The chemical formula of sodium carbonate is \[(Na_{2}CO_{3})\] and its molar mass is 106g/mol. It is an ionic compound- a sodium salt of carbonic acid and is composed of two sodium and one carbonate ion. 

Washing soda is hydrated sodium carbonate. The washing soda formula is \[(Na_{2}CO_{3}.10H_{2}O)\].

In this article, we will study sodium carbonate washing soda in detail.

Properties of Washing Soda

1. Physical Properties

• It is present in the form of monohydrated salts \[(Na_{2}CO_{3}.10H_{2}O)\], anhydrous salts \[(Na_{2}CO_{3})\], hepta-hydrous salts \[(Na_{2}CO_{3}.7H_{2}O)\], and deca-hydrous salts.

• Colour - greyish white powder

• Odour- odourless

• Taste- alkaline taste

• Melting point- 851

• Boiling point- decomposes

• Density - 2.54

• Stability- stable at ordinary temperature and atmospheric conditions, dries out in warm.

2. Chemical Properties

• It is stable but hygroscopic solid and readily dissolves in water to form slightly acidic carbonic acid and strong base sodium hydroxide. The aqueous solution of sodium carbonate is a strong base. It reacts violently with many acids, it decomposes to emit toxic fumes of disodium oxide.

Formation of Washing Soda

Solvay Process

This process is used for the manufacturing of washing soda. Here we will study the chemical equation of washing soda.

Materials required

1. Sodium chloride

2. Limestone

3. Ammonia gas

It consists of four steps-

1. Purification of Brine

2. Formation of sodium hydrogen carbonate

3. Formation of sodium carbonate

4. Recovery of ammonia

Step1: Purification of Brine

• At the first stage, a saturated solution of sodium chloride is prepared which is known as brine.

• Brine is concentrated through evaporation. Impurities are removed through precipitation.

• Sodium chloride brine is the first purified scaling of downstream process equipment and to prevent the contamination of the final product.

• After removing the impurities, a brine solution is then filtered and passed through an ammonium tower to dissolve ammonia. After purification, brine is contacted with ammonia gas.

Step 2: Formation of Sodium Hydrogen Carbonate

• The ammoniated brine is then sent to the carbonating columns where sodium carbonate is precipitated by contacting the brine with carbon dioxide.

\[NH_{3}(aq) + CO_{2}(g) + NaCl(aq) + H_{2}O \rightarrow  NaHCO_{3}(s) + NH_{4}Cl(aq)\]

Step 3: Formation of sodium carbonate:

• The suspended sodium hydrogen carbonate is removed from the carbonating tower and treated at 300C to produce sodium carbonate. 

\[2NaHCO_{3} \rightarrow  Na_{2}CO_{3} + CO_{2} + H_{2}O\]

• This carbon dioxide is recycled back into the carbonating tower.

Step 4: Recovery of ammonia: 

• Calcium oxide which was formed as a byproduct of the thermal decomposition of limestone in the lime kiln reacts with water to form calcium hydroxide. The calcium hydroxide reacts with ammonium chloride separated from the carbonating tower by filtration.

\[2NH_{4}Cl + Ca(OH)_{2} \rightarrow  2NH_{3} + CaCl_{2} + H_{2}O\]

• The ammonia is recycled back into the process to form ammoniated brine. Calcium chloride is formed as a by-product of the Solvay process.

Uses of Washing Soda

1. Used in industries and households as a cleaning agent. 

2. It finds its use in the industries of paper, textiles, soap, and detergent. 

3. It is used in the process of water softening. 

4. It is used in glass production. 

5. It is one of the laundry agents of greatest significance.

Did You know?

The ashes of burned plants are one common source of washing soda; for this reason, it is often called soda ash.

Light and dense soda ash are typically wrapped in multi-wall paper containers, plastic, or polyethene lined bags. Covered bottom discharge hopper cars are the most common rail cars used for bulk soda ash. 

Sodium carbonate is a brittle, crystalline substance that is susceptible to conveyor equipment breakage. Soda ash produces particles that are micron-sized and require high-efficiency collectors. 

Usually, soda ash is processed in a factory for a limited period. As a pile on the floor, it can be packed in bulk and retrieved by a front-end loader or other bulk-handling unit.

Applications of Sodium carbonate

Sodium carbonate is used in a variety of ways, that includes:

• Sodium carbonate is a cleaning agent used in the home for things like laundry. Sodium carbonate is a common element in dry soap powders.

• It is used to remove both temporary and persistent water hardness.

• It's used to make glass, soap, and paper, among other things.

• It's utilised in the production of sodium compounds, such as borax.

• Glass Manufacturer- Sodium carbonate acts as a silica flux, decreasing the melting point of the combination to a level that may be achieved without the need for specific ingredients. Because this "soda glass" is water-soluble, calcium carbonate is added to the melt mixture to make it insoluble. Melting sodium carbonate, calcium carbonate, and silica sand (silicon dioxide (SiO_{2)) into bottle and window glass (soda-lime glass) produce soda-lime glass. 

• Water Softening- Dissolved chemicals, mainly calcium or magnesium compounds, are present in hard water. Sodium carbonate is used to remove water hardness, both temporary and permanent.

• Food Additive- Sodium carbonate has a variety of culinary applications because it is a stronger base than baking soda but weaker than lye. Alkalinity influences gluten synthesis in kneaded doughs and increases browning by reducing the temperature at which the Maillard reaction occurs. To take advantage of the former effect, sodium carbonate is one of the ingredients in kansui, an alkaline salt solution used to give Japanese ramen noodles their distinctive flavour and chewy texture; a similar solution is used to produce lamian in Chinese cuisine for similar reasons.

• Inexpensive, weak base- Sodium carbonate is also employed in a variety of sectors as a moderately strong base. It is used as a common alkali in many chemical processes because it is less expensive and safer to handle than sodium hydroxide. Its gentleness makes it ideal for usage in residential settings.