Thursday, September 10, 2020

Properties Of Borax

Properties Of Borax:

  • Borax is a white crystalline solid, less soluble in water but more soluble in hot water.
  • Borax dissolved in hot water to gives the alkaline solution of boric acid and sodium hydroxide.

                        Na2B4O7  +  7H2O  ———>  4H3BO3  +  2NaOH

  • On heating, borax loses its water of crystallization and swells up to form a puff mass. On further heating, it melts into a clear liquid which solidified to a transparent glass like bead. Which consist of sodium metaborate and boric anhydride. This glass bead is commonly called as borax bead.                                                                                

                       Na2B4O7.10H20 ———> Na2B4O7 ———> 2Na2BO2 + B2O3

  • Borax beads are used in laboratory to identify some metals in salts, through borax beads test. Nickel salts give brown colored bead. Cobalt slats give blue colored bead. White chromium salt gives green bead in flame.
  • Borax reacts with acids like sulphuric acid and hydrochloric acid to form sparingly soluble boric acid.
                              Na2B4O7 + 2HCl + 7H2O  ———> 4H3BO3  +  2NaCl

                              Na2B4O7  +  H2SO4  +  5H2O  ———>  4H3BO3  +  2Na2SO4

  • Borax reacts with Ammonium Chloride to form boron nitride.

                              Na2B4O7  +  2NH4Cl  ———>  2NaCl  +  2BN  +  B2O3  +  2H2O

  • Borax heated with ethyl alcohol and concentrated sulphuric acid, to forms vapors of triethylborane. When ignited these vapor burn with green edged flame.

                  Na2B4O7  +  H2SO4  +  5H2O ———> Na2SO4  +  4H3BO3

                  H3BO3  +  3C2H5OH  ———>  B(OC2H5)3  +  3H2O

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