Question

In borax bead test characteristic colour appears due to formation of

Answer 1

Answer:

The answer is metal metaborates.

Explanation:

In the borax bead test, the bead is made up of an inert substance. The substance is adhered to a stick and then burnt on the flame, where it loses its water of crystallization and forms a transparent and colorless bead.

The bead is then cooled down and dipped into the substance to be tested. The coated bead is then heated in an oxidizing and reducing flame and different colors are observed.

Mostly the characteristic color appears due to the formation of metal metaborates salts of chromium, cobalt, and copper.

Answer 2

$\huge\mathcal\blue{Answer:}$

$\boxed{\red{\texttt{Borax\:bead\:test}}}$

Sodium tetaraborate decahydrate $\boxed{\green{Na_2B_4O_7.10H_2O}}$is called borax

On heating borax first it swells up due to the elimination of the water molecules. On further heating it melts to a liquid which then solidifies to a transparent glassy mass. It contains sodium meta borate and boric acid

$\red{Na_2B_4O_710H_2O}{\rightarrow}\blue{Na_2B_4O_7}{\rightarrow}\pink{2NaBO_2+B_2O_3}$

${B_2O_3}$ combines with meat oxides to form metal metaborates which form coloured beads. This reaction is called " Borax bead test"

$\blue{B_2O_3+CoO}{\rightarrow}\pink{Co(BO_2)_2}$