Washing soda

SODIUM CARBONATE (WASHING SODA)

It is a whitish, odorless powder. Its chemical formula is Na2CO3.

PRODUCTION OF SODIUM CARBONATE BY SOLVAY’S PROCESS

Washing soda is produced from sodium chloride (or common salt) by Solvay’s process involves the following three steps:

• A cold and concentrated solution of sodium chloride (called brine) is reacted with ammonia and carbon dioxide to obtain sodium hydrogencarbonate. Carbon dioxide involved is produced through calcium carbonate and the calcium oxide left is used in recovering ammonia from ammonium chloride. :

• Here, the Sodium hydrogen carbonate formed is only slightly soluble in water, so it precipitates out as a solid.
• Sodium bicarbonate is obtained which is then converted to sodium carbonate on heating.
  $2{\mathrm{NaHCO}}_{3 } \to {\mathrm{Na}}_2{\mathrm{CO}}_3 + {\mathrm{H}}_2\mathrm{O} + {\mathrm{CO}}_2$
• Recrystallisation of sodium carbonate gives washing soda. It is also a basic salt.
  ${\mathrm{Na}}_2{\mathrm{CO}}_3 + 10{\mathrm{H}}_2\mathrm{O} \to {\mathrm{Na}}_2{\mathrm{CO}}_3.10{\mathrm{H}}_2\mathrm{O}$

PROPERTIES OF SODIUM CARBONATE

• It is a transparent crystalline solid.
• It is one of few metal carbonates which are soluble in water and forms strongly alkaline water solution.
• The solution of washing soda in water is alkaline which turns red litmus to blue.
• Detergent properties (or Cleansing Properties): Washing soda has detergent properties (or cleansing properties) because it can remove dirt and grease from dirty clothes etc. Washing soda attacks dirt and grease to from water soluble products, which are then washed away on rinsing with water.
• Washing soda is hygroscopic and absorbs moisture from the air.

USES OF SODIUM CARBONATE

• It is used as a “cleansing agent” f or domestic purposes like is removing burnt-on grease from kitchen utensils, 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 such as borax.