Out of $BaC{l}_2$ and $KCl$, which one is more effective in causing coagulation of a negatively charged colloidal sol? Give reason.

According to the Hardy-Schulze rule, greater the valency of a flocculating ion the greater is its power to cause precipitation. Between $B{a}^{2+}$(from $BaC{l}_2$) and $K^{+}$ (from $KCl$), $B{a}^{2+}$ has greater valency. Therefore, $BaC{l}_2$ will be more effective in causing the coagulation of a negatively charged colloidal sol.