The amount of electrolyte required to coagulate the given colloid is in order NaCl>BaCl2<AlCl3 Because as colloids move towards anode they must be negatively charge. According to Hardy Schulze rule, Coagulation value ∝
1
Coagulatingpower(Chargeanelectrolyte)
The charge on the electrolyte; Na+,Ba2+ and Al3+ are 1, 2 and 3 respectively.