The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged, respectively. Which of the following statements is NOT correct?

1. ${\text{Fe(OH)}}_3$ is a positive sol; Gold is a negative sol.2. Mixing sols: When oppositely charged sols are mixed, they neutralize each other and coagulate (mutual coagulation). Thus, saying mixing has no effect is incorrect.3. Electrophoresis: Movement of particles toward electrodes leads to coagulation at the electrode. (Correct)4. Electrolytes: According to Hardy-Schulze rule, ${\text{Mg}}^{2+}$ (from ${\text{MgCl}}_2$) coagulates negative gold sol, while ${\text{Cl}}^{-}$ coagulates positive iron sol. Since ${\text{Mg}}^{2+}$ has a higher charge than ${\text{Cl}}^{-}$, it is more effective for gold. (Correct)