sentences:  The tetrahydrate consists of discrete, octahedral [(H2O)4Co(NO3)2] molecules.The hexahydrate is better described as hexaaquacobalt(II) nitrate, [Co(OH2)6][NO3]2, as it consists of discrete [Co(OH2)6]2+ and [NO3]− ions.Above 55 °C, the hexahydrate converts to the trihydrate and at higher temperatures to the monohydrate.