How borax can be prepared?

Answer 1

From tincal: Tincal is boiled with water and the so;ution is then filtered to remove impurities of sand, clay etc. The filterate is concentrated till crystallization begins and then cooled. The crystals of borax are separated by filteration.

From colemanite (Ca2B6O11):

Ca2B6O11 + 2Na2CO3 -----Heat-----» Na2B4O7 + 2NaBO2 + 2CaCO3↓

4NaBO2 + CO2 -----------» Na2B4O7 + Na2CO3

The insoluble calcium carbonate is filtered off .The remaing solution containg of borax and sod.metaborate is then treated with CO2 to convert sod.metaborate to borax.The solution is now concentrated and cooled to crystallize borax.

From boric acid : Borax is prepared from boric acid by boiling with soda ash. On cooling the solution, borax separates out.

4H3BO3 + Na2CO3 ------------» Na2B4O7 + 6H2O +CO2 ↑