Borax Bead Test – Uses, Procedure, and Precautions

The Borax Bead Test is a classical qualitative inorganic analysis test used to detect transition metal ions based on the color they impart to a transparent borax bead when heated in a flame. This Borax Bead Test is for colored basic radicals like Cu⁺² , Fe⁺³ , Mn⁺² , Co⁺² , Cr⁺³ and Ni⁺² .

The method was originally developed for mineral analysis and remains an important experiment in school and college chemistry laboratories.

Procedure of Borax Bead Test.

Prepare a loop of the platinum wire at the end. Heat the loop of platinum wire in the flame. Take a little powdered borax on the hot loop. Heat this borax on the flame. First of all the borax swells up. Then it melts into a colorless glass-like bead on the loop.

Now put a few grains of the substance on the bead which has a colored basic radical. Again heat it. Heating can be done on the oxidizing flame and then in the reducing flame. The colors of the beads are produced. From the nature of the color, the basic radical can be verified.

Chemistry of the Borax bead test:

When borax is fused on the loop of the platinum wire it is decomposed. Sodium metaborate is produced along with the metal oxide.

\mathrm{Na_2B_4O_7 \rightarrow 2NaBO_2 + B_2O_3}

When the compound is heated on the flame, then metal oxide is produced as CuO, Mn₂O₃, Cr₂O₃, NiO etc. These oxide combine with B₂O₃ to give the metaborates of these metals.

The metaborates of all the colored metal ions appear in the form of shining beads.

Example.

CuO gives Cu(BO₂)₂ which has a blue color in the oxidizing flame in the cold state, but when the bead is hot then the copper metaborate is green in color. Cu(BO₂)₂ is colorless in the reducing flame

\mathrm{CuO + B_2O_3 \rightarrow Cu(BO_2)_2}

Colors of Beads for Different Metals.

Uses Of Borax.

1. To prepare borate glass, which is heat resistant.
2. In the softening of water.
3. In borax bead test for the detection of metallic cations.
4. In metallurgical operations.
5. As a flux in welding
6. In making washing powders.
7. In leather industry for tanning and dyeing.
8. In cosmetics, soaps, textiles, paints, medicines, match industry and as a preservative.

Precautions of Borax Bead Test.

1. Always use a clean loop — contamination causes false colors.
2. Use a small amount of sample (just a trace).
3. Heat the bead properly in both oxidizing and reducing flames.
4. Allow the bead to cool before touching.
5. Use platinum or nichrome wire — copper wire must not be used.

Conclusion.

The Borax Bead Test is an elegant and simple method to identify transition metal ions through the color of the bead they produce. It demonstrates how electronic structure affects color formation, making it a valuable tool in inorganic qualitative analysis and chemical education.