preparation of borax Powder ?
Answers
From boric acid : Borax is prepared from boric acid by boiling with soda ash. On cooling the solution, borax separates out. It is a white crystalline solid, less soluble in cold water but more soluble in hot water. The aqueous solution of borax is alkaline due to hydrolysis.
Answer:
Borax (Na2B4O7.10H2O)
Borax is the sodium salt of boric acid. B orax occurs naturally as tincal (suhaga) in certain dried up lakes of india, Tibet, Srilanka and USA. It contains about 55% borax.
From Tincal: Tincal is boiled with water and the solution is then filtered to remove impurities of sand, clay etc. The filtrate is concentrated till crystallization begins and then cooled. The crystals of borax are separated by filtration.
From colemanite (Ca2B6O11):
Ca2B6O11 + 2Na2CO3 -----Heat-----» Na2B4O7 + 2NaBO2 + 2CaCO3↓
4NaBO2 + CO2 -----------» Na2B4O7 + Na2CO3
The insoluble calcium carbonate is filtered off .The remaining solution containing of borax and sodium metaborate is then treated with CO2 to convert sodium 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 ↑
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