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
• Correct answer
  C

  mixing the sols has no effect
• D

  coagulation in both sols can be brought about by electrophoresis

Hence, the correct answer is option: 'C'.