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?

• magnesium chloride solution coagulates, the gold sol more readily than the iron (III) hydroxide sol.

• sodium sulphate solution causes coagulation in both sols

• mixing the sols has no effect

• coagulation in both sols can be brought about by electrophoresis