Borax

Formula: Na₂B₄O₇·10H₂O

Properties

• Crystal system: monoclinic.
• Crystal shape: flat elongated hexagonal tablets.
• Stability on air: not stable. After few weeks starts dehydrating, developing growing white spots. Store in tightly closed container.

Preparation

Borax can be bought ready. However, it can be prepared too, by adding soda (NaHCO₃) to water suspension of boric acid (H₃BO₃):

4H₃BO₃ + 2NaHCO₃ → Na₂B₄O₇ + 7H₂O + 2CO₂(g)

Growing

I used the evaporation method. Growth is complicated by low solubility of borax at room temperature.

Solubility in water: 3.3g/100ml at room temperature, up to 30g in boiling water.

Safety

Borax is moderately toxic, avoid ingestion.

More photos

References

• Wiki
• Crystal growing site in russian