23. Tin

1. $H_2S$

$Sn^{2+}$ $+$ $S^{2-}$ $\longrightarrow$ $SnS$ - Walnut-brown precipitate - Sparingly soluble in $(NH_4)_2S$ - Soluble in $KOH$ - Soluble in fuming $HCl$ - Insoluble in $(NH_4)_2CO_3$ - Insoluble $NH_3$

2. $KOH$

$Sn^{2+}$ $+$ $2OH^-$ $\longrightarrow$ $Sn(OH)_2$ - White precipitate - Soluble in HCl - Soluble in a large excess of reagent: $Sn(OH)_2$ $+$ $OH^-$ $\longrightarrow$ $Sb(OH)_3^-$ - Trihydroxostannate(II)

3. NH_3

$Sn^{2+}$ $+$ $2OH^-$ $\longrightarrow$ $Sn(OH)_2$ - White precipitate - Soluble in HCl - Insoluble in excess reagent

4. $HgCl_2$

$HgCl_2....\longrightarrow Hg_2Cl_2..$ - Calomel - White precipitate $Hg_2Cl_2....$ $\longrightarrow$ $2Hg^0..$ - Mercury - Gray-black

5. Displacement

$Zn$ $+$ $Sn^{2+}$ $\longrightarrow$ $Zn^{2+}$ $+$ $Sn^0$ - Crystalline deposit on the zinc