To an aqueous solution containing ions such as,

 ${\mathrm{Al}}^{+3},{\mathrm{Zn}}^{+2},{\mathrm{Ca}}^{+2},{\mathrm{Fe}}^{+3},{\mathrm{Ni}}^{+2},{\mathrm{Ba}}^{+2}$ and ${\mathrm{Cu}}^{+2}$. Conc $HCl$ was added followed by ${\mathrm{H}}_2\mathrm{S}$. The total number of cations precipitated during this reaction is/are