${\mathrm{Na}}_2{\mathrm{CO}}_3$ cannot be used to identify

${\mathrm{SO}}_3^{2-},{\mathrm{S}}^{2-}$ and ${\mathrm{SO}}_4^{2-}$ salts form comparatively stronger acids  (than ${\mathrm{H}}_2{\mathrm{CO}}_3\text{ ) }$in solution hence evolve  $C{O}_2$ with ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solution and give effervesence. While ${\mathrm{CO}}_3^{2-}$ does not react with ${\mathrm{Na}}_2{\mathrm{CO}}_3$ solution.