Coagulation power depends on nature of charge and amount of charge
Coagulation power $\propto$ charge on ion of electrolyte
As Arsenic sulphoid sol is negatively charged so for it cations will cause precipitation of ions and the order is $\mathrm{A}{\mathrm{l}}^{3+}>\mathrm{B}{\mathrm{a}}^{2+}>\mathrm{N}{\mathrm{a}}^{+}$
As Ferric hydroxide sol is positively charged so for it anions will cause precipitation of ions and the order is ${\left[\mathrm{F}\mathrm{e}{\left(\mathrm{C}\mathrm{N}\right)}_6\right]}^{4-}>\mathrm{P}{\mathrm{O}}_4^{3-}>\mathrm{S}{\mathrm{O}}_4^{2-}>\mathrm{C}{\mathrm{l}}^{-}$