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?
(a) Magnesium chloride solution coagulates, the gold sol more readily than the iron (III) hydroxide sol
(b) Sodium sulphate solution causes coagulation in both sols
(c) Mixing of the sols has no effect
(d) Coagulation in both sols can be brought about by electrophoresis
