Q.What is the borax-bead test used for in qualitative inorganic analysis? Briefly describe what happens when borax is strongly heated and the resulting bead is touched to a coloured metal salt.

[!TLDR] The borax-bead test heats borax into a glassy NaBO2/B2O3 bead, which forms a characteristically coloured metaborate when touched to a metal salt — used to identify the metal. [!ANSWER] Strongly heated borax first loses water and fuses into a clear glassy bead of sodium metaborate + boron oxide; touching this hot bead to a coloured meta …

The borax-bead test is a classic, simple qualitative-inorganic-analysis technique used to help identify certain transition metals in a sample. A small amount of solid borax, held on a loop of platinum or nichrome wire, is heated strongly in a flame; it first loses its water of crystallisation and swells up, then fuses into a clear, colourless, glassy bead. This bead is chemically a mixture of sodium metaborate ($\text{NaBO}_2$) and boron oxide ($\text{B}_2\text{O}_3$), formed as the borax loses water on strong heating (the same kind of dehydration chemistry described for boric acid). While still hot, this glassy bead is touched to a small amount of a coloured metal salt and then reheated in the flame; the metal oxide dissolves into the molten borax-derived glass, and the resulting metaborate compound formed typically has a characteristic colour — for example, a blue bead commonly indicates the presence of cobalt, while a bead that is green in the oxidising flame commonly indicates chromium or copper — and the colour can sometimes differ depending on whether the bea …

Describe how heating borax produces the glassy NaBO2/B2O3 bead, then explain how touching it to a metal salt and re …

Omitting that the bead itself is chemically NaBO2 + B2O3, describing it vaguely as 'melted borax'; forgetting that the colour observed is …