Borax [Chemical formula, Physical, Chemical Properties and Reactions]
By: Prof. Dr. Fazal Rehman Shamil | Last updated: February 3, 2024

The chemical formula of borax is Na₂B₄O₇·10H₂O.

Physical Properties of Borax:

Properties	Details
Appearance	White crystalline solid
Boiling Point	Decomposes at high temperatures
Crystal Structure	Monoclinic
Density	1.73 g/cm³
Electrical Conductivity	Poor conductor of electricity
Hardness	2 – 2.5 (Mohs scale)
Melting Point	741 °C (1,366 °F)
Odor	Odorless
Solubility	Soluble in water
Thermal Conductivity	Low thermal conductivity
Transparency	Transparent to translucent

Chemical Properties of Borax:

Properties	Details
Chemical Formula	Na2B4O7·10H2O (Sodium borate decahydrate)
pH	Alkaline (pH ~9)
Hygroscopicity	It readily absorbs moisture from the air.
Decomposition	Decomposes when heated, releasing water and forming sodium metaborate, anhydrous borax, and boric acid.
Reactivity with Acids	Reacts with acids to form boric acid and a corresponding salt.
Reaction with Metals	Can form complexes with certain metals, such as borax bead test for identification of metal ions.
Flame Color Test	Gives a green flame color when heated in a flame due to the presence of boron.
Reducing Agent	It acts as a reducing agent in certain chemical reactions.
Complex Formation	Can form complexes with various compounds and ions.
Glass Formation	Borax is used in glass production as a flux to lower the melting point and improve the glass quality.

Reaction of borax with Alkali Metal

Alkali Metal	Reaction with Borax
Lithium (Li)	2 Li + Na₂B₄O₇·10H₂O → 2 NaLiB₄O₇ + H₂ ↑
Sodium (Na)	2 Na + Na₂B₄O₇·10H₂O → 4 Na2B₄O₇+ H₂↑
Potassium (K)	2 K + Na₂B₄O₇·10H₂O → 2 KNaB₄O₇ + H₂ ↑
Rubidium (Rb)	2 Rb + Na₂B₄O₇·10H₂O → 2 RbNaB₄O₇ + H₂↑
Cesium (Cs)	2 Cs + Na₂B₄O₇·10H₂O → 2 CsNaB₄O₇ + H₂↑
Francium (Fr)	2 Fr + Na₂B₄O₇·10H₂O → 2 FrNaB₄O₇ + H₂↑

Reaction of borax with Alkaline Earth Metal

Alkaline Earth Metal	Reaction with Borax
Beryllium (Be)	2 Be + Na₂B₄O₇·10H₂O → 2 NaBeB₄O₇ + H₂↑
Magnesium (Mg)	2 Mg + Na₂B₄O₇·10H₂O → 2 NaMgB₄O₇ + H₂↑
Calcium (Ca)	2 Ca + Na₂B₄O₇·10H₂O → 2 NaCaB₄O₇ + H₂↑
Strontium (Sr)	2 Sr + Na₂B₄O₇·10H₂O → 2 NaSrB₄O₇ + H₂ ↑
Barium (Ba)	2 Ba + Na₂B₄O₇·10H₂O → 2 NaBaB₄O₇ + H₂↑
Radium (Ra)	2 Ra + Na₂B₄O₇·10H₂O → 2 NaRaB₄O₇ + H₂↑

Reaction of borax with Transition Metal

Transition Metal	Reaction with Borax
Iron (Fe)	Fe + Na₂B₄O₇·10H₂O → NaFeB₄O₇ + H₂↑
Copper (Cu)	2 Cu + Na₂B₄O_7.10H₂O → 2 NaCuB₄O₇ + H₂↑
Zinc (Zn)	Zn + Na₂B₄O₇·10H₂O → NaZnB₄O₇ + H₂↑
Nickel (Ni)	2 Ni + Na₂B₄O₇·10H₂O → 2 NaNiB₄O₇ + H₂↑
Cobalt (Co)	Co + Na₂B₄O₇·10H₂O → NaCoB₄O₇ + H₂↑
Chromium (Cr)	Cr + Na₂B₄O₇·10H₂O → NaCrB₄O₇ + H₂↑
Manganese (Mn)	3 Mn + 2 Na₂B₄O₇·10H₂O → 3 Na₂MnB₄O₇ + 2 H₂↑
Titanium (Ti)	2 Ti + 3 Na₂B₄O_7.10H₂O → 2 Na₂TiB₄O₇ + 3 H₂↑
Vanadium (V)	2 V + 3 Na₂B₄O₇·10H₂O → 2 Na₂VB₄O₇ + 3 H₂↑
Molybdenum (Mo)	3 Mo + 4 Na₂B₄O₇·10H₂O → 2 Na₆Mo₂B₈O₂₇ + 4 H₂↑
Tungsten (W)	W + 4 Na₂B₄O₇·10H₂O → Na₄W₂B₁₂O₃₁ + 4 H₂↑
Silver (Ag)	Ag + Na₂B₄O₇·10H₂O → NaAgB₄O₇ + H₂↑
Gold (Au)	2 Au + 3 Na₂B₄O₇·10H₂O → 2 Na₃AuB₄O₇+ 3 H₂↑

Reaction of borax with Non-Transition Metal

Non-Transition Metal	Reaction with Borax
Aluminum (Al)	2 Al + 3 Na₂B₄O₇·10H₂O → 3 NaAlB₄O₇ + 3 H₂↑
Magnesium (Mg)	Mg + Na₂B₄O₇·10H₂O → NaMgB₄O₇ + H₂↑
Calcium (Ca)	Ca + Na2B4O7·10H₂O → NaCaB₄O₇ + H₂↑
Sodium (Na)	2 Na + Na₂B₄O₇·10H₂O → 4 Na₂B₄O₇ + H₂↑
Potassium (K)	2 K + Na₂B₄O₇·10H₂O → 2 KNaB₄O₇ + H₂↑
Lithium (Li)	2 Li + Na₂B₄O₇·10H₂O → 2 NaLiB₄O₇ + H₂↑
Beryllium (Be)	2 Be + Na₂B₄O₇·10H₂O → 2 NaBeB₄O₇ + H₂↑
Barium (Ba)	2 Ba + Na₂B₄O₇·10H₂O → 2 NaBaB₄O₇ + H₂↑
Strontium (Sr)	2 Sr + Na₂B₄O₇·10H₂O → 2 NaSrB₄O₇ + H₂↑
Radium (Ra)	2 Ra + Na₂B₄O₇·10H₂O → 2 NaRaB₄O₇ + H₂↑
Aluminum (Al)	2 Al + 3 Na₂B₄O₇·10H₂O → 3 NaAlB₄O₇ + 3 H₂↑
Gallium (Ga)	2 Ga + 3 Na₂B₄O₇·10H₂O → 2 NaGaB₄O₇ + 3 H₂↑
Indium (In)	2 In + 3 Na₂B₄O₇·10H₂O → 2 NaInB₄O₇ + 3 H₂↑
Thallium (Tl)	2 Tl + 3 Na₂B₄O₇·10H₂O → 2 NaTlB₄O₇ + 3 H₂↑

Reaction of borax with Non-Metal

Non-Metal	Reaction with Borax
Hydrogen (H)	2 H2 + Na₂B₄O₇·10H₂O → 4 NaBO₂ + 9 H₂O
Carbon (C)	C + 2 Na₂B₄O₇·10H₂O → Na₂B₄O₇+ Na₂CO₃ + CO₂ ↑ + 10 H₂O
Nitrogen (N)	4 NH₄ + Na₂B₄O₇·10H₂O → Na₂B₄O₇ + 4 NaOH + 8 H₂O + N₂ ↑
Oxygen (O)	4 Na₂B₄O₇·10H₂O → 2 Na₂B₈O₁₃ + 13 H₂O + 3 O₂↑
Phosphorus (P)	2 P4 + 15 Na₂B₄O₇·10H₂O → 14 NaBO₂+ Na₃PO₄ + 30 H₂O
Sulfur (S)	8 S + 15 Na₂B₄O₇·10H₂O → 15 NaBO₂+ Na₂S₂O₃ + 30 H₂O
Fluorine (F)	2 F2 + 4 Na₂B₄O₇·10H₂O → 8 NaBO₂+ 2 NaBF₄ + 20 H₂O + O₂ ↑
Chlorine (Cl)	4 Cl2 + 8 Na₂B₄O₇·10H₂O → 16 NaBO₂+ 2 Na₂B₆O₁₀Cl₂ + 40 H₂O + O₂ ↑
Bromine (Br)	4 Br2 + 8 Na₂B₄O₇·10H₂O → 16 NaBO₂+ 2 Na₂B₆O₁₀Br₂ + 40 H₂O + O₂ ↑
Iodine (I)	4 I2 + 8 Na₂B₄O₇·10H₂O → 16 NaBO₂+ 2 Na₂B₆O₁₀I₂ + 40 H₂O + O2 ↑

Reaction of borax with Metalloid

Metalloid	Reaction with Borax
Boron (B)	2 B + 3 Na₂B₄O₇·10H₂O → Na₂B₄O₇ + 6 NaBO₂+ 6 H₂ ↑
Silicon (Si)	2 Si + Na₂B₄O₇·10H₂O → Na₄SiO₄ + 5 NaBO₂+ 10 H₂↑
Germanium (Ge)	2 Ge + Na₂B₄O₇·10H₂O → Na₄GeO₄ + 5 NaBO₂+ 10 H₂↑
Arsenic (As)	2 As + 5 Na₂B₄O₇·10H₂O → Na₄AsO₄ + 5 NaBO₂+ 10 H₂↑
Antimony (Sb)	2 Sb + 5 Na₂B₄O₇·10H₂O → Na₄SbO₄ + 5 NaBO₂+ 10 H₂↑
Tellurium (Te)	2 Te + 5 Na₂B₄O₇·10H₂O → Na₄TeO₄ + 5 NaBO₂+ 10 H₂↑
Polonium (Po)	2 Po + 5 Na₂B₄O₇·10H₂O → Na₄PoO₄ + 5 NaBO₂ + 10 H₂↑

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