Borax Bead Test.
The test is for coloured basic radicals like Cu+2, Mn+2,Co+2,Cr+3, and Ni+2.
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 colourless glass-like bead on the loop.
Now put a few grains of the substance on the bead which has a coloured basic radical. Again heat it. Heating can be done on the oxidizing flame and then in the reducing flame. The colours of the beads are produced. From the nature of the colour, like 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. When the compound is heated on the flame, then metal oxide is produced as Cuo, Mn2O3, Cr2O3, NiO etc. These oxides combine with B2O3 to give the metaborates of these metals.
The metaborates of all the coloured metal ions appear in the form of shining beads.
CuO gives Cu(BO2)2 which has a blue colour in the oxidizing flame in the cold state, but when the bead is hot then the copper metaborate is green in colour. Cu(BO2)2 is colourless in the reducing flame
Uses of Borax:
Borax is used:
- To prepare borate glass, which is heat resistant.
- In the softening of water.
- In borax bead test for the detection of metallic cations.
- In metallurgical operations.
- As a flux in welding.
- In making washing powders.
- In the leather industry for tanning and dyeing.
- In cosmetics, soaps, textiles, paints, medicines, match industry and as a preservative.