The Borax Bead Test is a preliminary dry test used to identify certain metal cations based on the color of the bead formed.

1. Bead Formation: When Borax ($N{a}_2{B}_4{O}_7\cdot 10H_{2}O$) is heated on a platinum wire loop, it swells and then shrinks into a transparent, glassy bead of Sodium metaborate ($NaB{O}_2$) and Boric anhydride ($B_2{O}_3$).
2. Reaction: The bead is touched to the salt and heated again. The metal oxide reacts with $B_2{O}_3$ to form colored Metal Metaborates.

• Examples: Copper (blue-green), Cobalt (deep blue), Chromium (green), Manganese (violet/pink).