Boron

 

Boron

Chemical formula	{{#Chem:B}}
Atomic Number	5
OTP appearance	solid
Molar Mass(g/mol)	10.81
Density(g/cc)	2.33 to 2.53
Melting Point(°C)	2076
Boiling Point(°C)	3927
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: {{#Chem: Na2B4O7(H2O)10 + 2 HCl = 5 H2O + 2 NaCl + 4 H3BO3 }}

   Kernite: {{#Chem: Na2B4O6(OH)2(H2O)3 + 2 HCl+ H2O = 2 NaCl + 4 H3BO3}}

   Colemanite: {{#Chem: CaB3O4(OH)3(H2O) + H2SO4 + H2O = CaSO4 + 3 H3BO3}}

   Howlite: {{#Chem: Ca2B5SiO9(OH)5 + 2 H2SO4 + 3 H2O = SiO2 + 2 CaSO4 + 5 H3BO3}}

2. Produce boric oxide via thermal decomposition of boric acid

   {{#Chem: 2H3BO3 { = 300°C } B2O3 + 3H2O}}

3. Produce elemental boron via magnesiothermic reduction of boric oxide

   {{#Chem: B2O3 + 3Mg = 2B + 3MgO}}