Phase transition in Na(2)SO(4): all five polymorphic transformations in DSC

In this investigation, we have characterized the Na(2)SO(4) using differential scanning calorimetry (DSC). It is well known that Na(2)SO(4) exhibits five polymorphs. However, the experimental evidence for all five polymorphs has never been observed in DSC. In this investigation, the five polymorphic transformations have been observed in heating cycle. Furthermore, the transition I-II is observed, which is not reversible. In addition, phase transition temperature for V -> IV and IV -> III transition appears to be much closed and may get unnoticed