Which of the following statements is not correct?

Muddy water can be coagulated more effectively by alum as compared to NaCl.

Surface tension of lyophilic colloids is less than that of the dispersion medium.

When excess ${\mathrm{AgNO}}_3$ solution is added to Kl sol and the resultant colloidal state is subjected to electrophoresis, coagulation will be observed near anode.

Ferrimagnetic substance on heating show paramagnetic behaviour.