A solution containing a period$-\mathrm{IV}$ cation gives a precipitate on passing ${\mathrm{H}}_2\mathrm{S}.$ A solution of this precipitate in dil. $\mathrm{HCl}$produces a white precipitate with $\mathrm{NaOH}$ solution and bluish-white precipitate with basic potassium ferrocyanide. The cation is