[Co (NH3)5Cl] SO4 gives white precipitate with BaCl2 solution while [Co (NH3 )5SO4 ] Cl does not respond to this test. On contrary to this, [Co (NH3)5SO4] Cl gives white precipitate with silver nitrate solution while [Co (NH3)5Cl] SO4 does not respond to this test. These observations confirm that [Co (NH3)5Cl] SO4 and [Co (NH3)5SO4] Cl are ionisation isomers.