${\mathrm{Al}}^{3+}$ and ${\mathrm{Fe}}^{3+}$ sulphides hydrolyse in water. ${\mathrm{Ni}}^{2+}$ and ${\mathrm{Zn}}^{2+}$ require basic medium with ${\mathrm{H}}_2 \mathrm{S}$ to form precipitate.  ${\mathrm{Ca}}^{2+}$ and ${\mathrm{Ba}}^{2+}$ sulphides are also soluble.  only ${\mathrm{Cu}}^{2+}$ can form the precipitate with ${\mathrm{H}}_2\mathrm{S}$ in the acidic medium.