An aqueous solution of aluminium sulphate would show

${\mathrm{Al}}_2{\left({\mathrm{SO}}_4\right)}_3$ is a salt of weak base ${\mathrm{Al}}_{ }{\left(\mathrm{OH}\right)}_3$  and strong acid  ${\mathrm{H}}_2{\mathrm{SO}}_4$.Salt of weak base and strong acid undergo cationic hydrolysis.