Boron

 

Boron

Chemical formula	B
Atomic Number	5
OTP appearance	solid
Molar Mass(g/mol)	10.81
Melting Point(°C)	2076
Boiling Point(°C)	3927
Density(g/cc)	2.33 to 2.53
NFPA 704	3 2 0

Elemental Boron is rarely required. Normally it is used in a reduced state.

Uses

Justification Questioned

Primary

• Borosilicate glass (as oxide)
• Feedstock for sodium borohydride

Secondary

• Detergents (as sodium tetraborate)
• Fire retardants for wood and cloth
• Semiconductor dopant
• High-hardness metal alloys

Natural Occurrence

• Elemental boron does not occur naturally.
• sodium boron hydroxide occurrs in the minerals kernite and borax
• calcium boron hydroxide occurrs as the mineral colemanite

Production

Extraction

1. Produce boric acid by combining the boron ore with a mineral acid such as hydrochloric, sulfuric or phosphoric

   Borax: Na₂B₄O₇(H₂O)₁₀ + 2 HCl → 5 H₂O + 2 NaCl + 4 H₃BO₃

   Kernite: Na₂B₄O₆(OH)₂(H₂O)₃ + 2 HCl + H₂O → 2 NaCl + 4 H₃BO₃

   Colemanite: CaB₃O₄(OH)₃(H₂O) + H₂SO₄ + H₂O → CaSO₄ + 3 H₃BO₃

   Howlite: Ca₂B₅SiO₉(OH)₅ + 2 H₂SO₄ + 3 H₂O → SiO₂ + 2 CaSO₄ + 5 H₃BO₃

2. Produce boric oxide via thermal decomposition of boric acid

   2 H₃BO₃

   {

   →

   300°C}

   B₂O₃ + 3 H₂O

3. Produce elemental boron via magnesiothermic reduction of boric oxide

   B₂O₃ + 3 Mg → 2 B + 3 MgO