In the wet tests for detection of various cations by precipitation, Ba 2 + cations are detected by obtaining…

${\mathrm{Ba}}^{2+}$ belongs to ${\mathrm{V}}^{\text{th }}$Group and hence they are precipitated with ${\mathrm{CO}}_3^{2-}$ to give ppt of ${\mathrm{BaCO}}_3$. In Wet tests for cations, $({\mathrm{NH}}_4{)}_2{\mathrm{CO}}_3$ is used as a group reagent for fifth group cations$({\mathrm{Ba}}^{2+},{\mathrm{Ca}}^{2+},{\mathrm{Sr}}^{2+})$.

${\mathrm{Ba}}^{2+}+({\mathrm{NH}}_4{)}_2{\mathrm{CO}}_3\to {\mathrm{BaCO}}_3+{{\mathrm{NH}}_4}^{\oplus }$