Boron

Elementary boron is a brown/black solid with a slight metal-like lustre. It is a semiconductor. It is very inert. It is not even attacked by boiling hydrochloric or hydrofluoric acid. Highly concentrated hot nitric acid very slowly dissolves the element, when it is finely powdered. For this reason, elementary boron is not interesting from the point of view of the home chemist. It can, however, be purchased through eBay from chemical elements-collector items suppliers. The element is hard to obtain in a really pure state and for this reason, pure boron samples are remarkably expensive. The element itself is not rare at all, so its compounds are not expensive at all. The element usually has oxidation state +3 in its compounds.

Although the element is not interesting for the home lab, some of its compounds are:

• sodium tetraborate, Na₂B₄O₅(OH)₄·8H₂O  (borax)
• sodium perborate, NaBO₃·4H₂O
• sodium borohydride, NaBH₄
• boric acid, B(OH)₃

Sodium tetraborate can be purchased at many drugstores, and it is also available at photography raw chemical suppliers. It is an interesting chemical, which can be used to perform nice experiments in the formation of colored precipitates. Many transition metals form precipitates with tetraborates of diverse colors. The salt can also be used for preparing mildly alkaline solutions. Borax is a white or transparent solid, which moderately easily dissolves in water. When the solid is heated, a foam-like white solid is formed, which cannot easily be dissolved in water anymore.

Sodium perborate usually is not used because of its boron-content, but because of the presence of a peroxo-group in the compound. For this reason, this compound is discussed on the page about oxygen.

Sodium borohydride is a white crystalline solid, which easily dissolves in water. Solutions of this compound slowly evolve hydrogen. When the solution is made strongly alkaline, then this compound is more stable in solution. On addition of an acid to a solution of sodium borohydride a lot of hydrogen is produced. This compound is very useful, because it is a strong reductor. It is capable of reducing many metal salts to the metallic state. A nice property of this reductor is that its reaction products are colorless and soluble as well. This compound can be purchased at some photography raw chemical suppliers. This compound is fairly dangerous. It must be stored absolutely dry. When it is used in experiments, then its solutions should be handled carefully. With strong acids and with strong oxidizers very violent reactions may occur.

Boric acid is a white solid, which can be purchased at many drugstores and at photography raw chemical suppliers. It is available as powder, which only dissolves in water very slowly or as a crystalline solid, which dissolves in water somewhat easier. This compound is an extremely weak acid, but in combination with many alcohols, borate-esters are formed very easily and the compound acts as a much stronger acid. When alcohols with boric acid dissolved in them are burned, then they burn with a green flame. In combination with borax, buffer solutions can be prepared at low cost.

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