Borax Preparation

 Borax  [Na₂B₄O₇.10H₂O]              

          Borax is a sodium salt of tetraboric acid. Fine powdered colemanite ( Ca₂B₆O₁₁ ).    Is boiled with sodium carbonate ( washing soda ) solution. The insoluble calcium carbonate is filtered off ( CaCO₃ ).  Then it is concentrated and cooled to get the crystals of borax. The sodium metaborate is treated with           CO₂  gas which converts into borax.

Ca₂B₆O₁₁  +  2Na₂CO₃  ———>  Na₂B₄O₇     +      2NaBO₂         +        2CaCO₃

Colemanite                                  Borax                 Sodium                     calcium

                                                                            metaborate                carbonate

2NaBO₂  +  CO₂  ———>  Na₂B₄O₇  +  Na₂CO₃