On the nature of crystallization water using thermal analysis. - The application to some hydrates with different cations

The nature of the crystallization water in some hydrates with different cations, namely: MnSO4·H2O; FeSO4·7H2O; CoSO4·7H2O; NiSO4·7H2O, has been studied by the application of the following non-isothermal techniques: thermogravimetry (TG), derivative thermogravimetry (DTG), and differential thermal analysis (DTA). Analysis of the characteristic thermogravimetric data (Tm, Wμand of the kinetic parameters (n, Ea) calculated from DTG and DTA data - with CuSO4·5H2O as a reference - demonstrated the existence of crystallization and anion water in the studied hydrates. The activation energy of the process of anion water elimination does not depend on the nature of the cation. This conclusion was confirmed by the absence of the compensation effect in this process.