In this octahedral complex with the molecular composition $\mathrm{Co} \cdot 5 \mathrm{NH}_3 \cdot \mathrm{Cl}^2 \cdot \mathrm{SO}_4$, two isomers, A and B, are present.

Isomer A is represented as $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5\left(\mathrm{SO}_4\right)\right] \mathrm{Cl}$. When this isomer is dissolved in solution, it reacts with $\mathrm{AgNO}_3$, forming a white precipitate of silver chloride ($\mathrm{AgCl}$).

Isomer B is written as $\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}\right] \mathrm{SO}_4$. In solution, it reacts with $\mathrm{BaCl}_2$, forming a white precipitate of barium sulfate ($\mathrm{BaSO}_4$).

These two isomers demonstrate ionisation isomerism. This type of isomerism occurs when the exchange of ions inside and outside the coordination sphere of a complex leads to the formation of isomers with different chemical behaviors in solution.