Chemistry - Complete Pblock- Question with Solution | TestHub

On heating, borax first loses water molecules and swells up. On further heating it turns into a transparent liquid, which solidifies into glass like material known as borax bead. The metaborates of many transitions metals have characteristic colours and, therefore, borax bead test can be used to identify them in the laboratory. For example, When borax is heated in a Bunsen burner flame with CuO on a loop of platinum wire, a bluegreen coloured $\mathrm{Co}{\left({\mathrm{BO}}_2\right)}_2$ bead is formed in non-luminous flame and colouless ${\mathrm{CoBO}}_2$ is formed on heating in luminous flame.