Question

Alum is used by dyer for :

• A. For fire-proofing fabrics
• B. As first aid for cuts
• C. For softening hard water
• D. As mordant

Answer 1

Answer: (D)

As mordant

Answer 2

As a mordant in dye industry. The fabric which is to be dyed is dipped in a solution of the alum and heated with steam. Al(OH)3 obtained as hydrolysis product of [Al(H2O)6]3+ deposits into the fibres and then the dye is absorbed on Al(OH)3.