Production of salt

Production of salt 

The places where salt produced are referred to as saltterns. In Sri Lanka two main saltterns are placed in Puttalam and Hambantota. 

♣Characteristic features of the places where saltterns are established♣ 

☀ Plane land by the sea or lagoon  

☀ Less rainfall 

☀ Dry air, more sunlight  

☀ Water impervious clay sand 

➨Sea water is used as the raw material. 

 ☆ 

☀Sea water is pumped into the first tank of the salttern. The sea water is evaporated by sunlight.  

When the concentration of sea water increases CaCO3 gets precipitated in 

the first tank of the salttern.  

CaCO3 precipitate is allowed to settle down.

☆ 

☀ Remaining solution is transferred into the second tank of the salttern and evaporated 

by sunlight. When the concentration further increases CaSO4 gets precipitated. 

☆ 

☀ Remaining solution is transferred into the third tank of the salttern and evaporated. 

When the concentration further increases NaCl gets precipitated. NaCl is removed 

from the third tank of the salttern. This NaCl contains Ca2+, Mg2+ and SO4 

2- as impurities. 

☀ Pure NaCl is not hygroscopic. But NaCl having the impurities is hygroscopic. Sodium chloride collected from the third tank is stored outside for nearly six months. During this storage period NaCl is almost purified as Ca2+ and Mg2+ salts absorb water from air and become solution while NaCl remains as a solid. 

➣  Iodized salt is produced by mixing with KIO3. 

♣ Uses of NaCl ♣ 

☀ Cooking 

☀ Food preservative (Maldivian fish, Pickle) 

☀ Manufacture of Na metal, Na2CO3, NaHCO3 and NaOH 

☀ Saline 

☀To reduce the melting point of ice 

☛As Mg2+ and Br- concentrations are high in bittern soultion it can be used to produce Mg and Br2.

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