Question

Borax bead test is given by :

• A. An aluminium salt
• B. A cobalt salt
• C. A copper (II) salt
• D. A nickel salt

Answer 1

Answer: (B), (C), (D)

The correct options are
B

A cobalt salt

C

A copper (II) salt

D

A nickel salt

(B, C, D)

Borax powder is taken in a hot platinum wire loop and held over the flame. The heat forces the loss of water of crystallization and eventually, the loop has a colourless, glassy bead:

$N{a}_2{B}_4{O}_7.10H_{2}O\underset{-10H_{2}O}{\overset{\Delta }{\to }}2NaB{O}_2+B_2{O}_3$

The glass bead is scraped over a sample of the coloured salt and heated again. Based on the colour of the bead observed, we can determine the (coloured) cation!

Cr, Mn, Fe, Co, Ni, and Cu give these tests. This test is applicable only for coloured salts. Aluminium doesn't give positive results.