The coagulation values in millimoles per litre of the electrolytes used for the coagulation of ${As}_2{ S}_3$ are given :

I. $\left(NaCl\right)=52$

II. $\left({BaCl}_2\right)=0.69$

III. $\left({MgSO}_4\right)=0.22$

Correct order of their coagulating power is

Given, The coagulation values in millimoles per litre of the electrolytes used for the coagulation of ${As}_2{ S}_3$.

Lower the coagulation power, higher is the value of coagulation in millimoles per liter. Coagulation power is inversely proportional to the coagulation value. 

$\text{ Coagulation power }\propto \frac{1}{\text{ Coagulation value }}$

The order of coagulation power is III > II > I

Therefore, option C is correct.