Mixing of equivalent amount of yellow As2O3 sol with red Fe(OH)3 sol gives rise to a colourless solution

Question

Explain giving reasons:

Mixing of equivalent amount of yellow As₂O₃ sol with red Fe(OH)₃ sol gives rise to a colourless solution along with a sediment.

Answer 1

In As₂O₃ sol colloidal particles are negatively charged, while Fe(OH)₃ particles are positively charged. So the particles mutually discharge each other and coagulation occurs. Solution thus becomes colourless and sediments of Fe(OH), and As₂O₃ separate.