A colorless aqueous solution contains nitrates of two metals, $\mathbf{X}$ and $\mathbf{Y}$. When it was added to an aqueous solution of $\mathrm{NaCl}$, a white precipitate was formed. This precipitate was found to be partly soluble in hot water to give a residue $\mathbf{P}$ and a solution $\mathbf{Q}$. The residue $\mathbf{P}$ was soluble in aq. $\mathrm{NH}_{3}$ and also in excess sodium thiosulfate. The hot solution $\mathbf{Q}$ gave a yellow precipitate with KI. The metals $\mathbf{X}$ and $\mathbf{Y}$, respectively, are