Baking Soda

Chemically baking soda is sodium hydrogen carbonate, NaHCO3.

Manufacture

Baking soda is manufactured by Solvey’s process. It is mainly used for manufacturing washing soda but baking soda is obtained as an intermediate.

Raw Materials Required

The raw materials required to manufacture washing soda are:

  1. Lime stone which is calcium carbonate, CaCO3
  2. Sodium chloride (NaCl) in the form of brine (Conc. NaCl Solution)
  3. Ammonia (NH3)

Process

In Solvey's process, carbon dioxide is obtained by heating limestone strongly.

CaCO3 (s) → CaO (s) + CO2 (g) ↑

It is then passed through cold brine (a concentrated solution of NaCl in water) which has previously been saturated with ammonia.

NaCl (aq) + CO2 (g) + NH3 (g) + H2O (l) ⎯→ NaHCO3 (s) ↓ + NH4Cl (aq)

NaHCO3 is sparingly soluble in water and crystallises out as white crystals. Its solution in water is basic in nature. It is a mild and non-corrosive base.

Action of heat: On heating, sodium hydrogen carbonate is converted into sodium carbonate and carbon dioxide is given off.

2NaHCO3 + heat → Na2CO3 + H2O + CO2

Use

  1. Used for cooking of certain foods.

  2. For making baking power (a mixture of sodium hydrogen carbonate and tartaric acid). On heating during baking, baking soda gives off carbon dioxide. It is this carbon dioxide which raises the dough. The sodium carbonate produced on heating the baking soda gives a bitter taste. Therefore, instead of using the baking soda alone, baking powder is used. The tartaric acid present in it neutralises the sodium carbonate to avoid its bitter taste. Cakes and pastries are made flufly and soft by using baking powder.

  3. In medicines: Being a mild and non-corrosive base, baking soda is used in medicines to neutralise the excessive acid in the stomach and provide relief. Mixed with solid edible acids such as citric or tartaric acid, it is used in effervescent drinks to cure indigestion.

  4. In soda acid fire extinguishers.