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Study of the nature of the crystallization water in some magnesium hydrates by thermal methods


The nature of the crystallization water in MgSO4·7H2O, Mg(NO3)2·6H2O and MgCl2·6H2O has been studied with the nonisothermal methods of thermogravimetry (TG), derived thermogravimetry (DTG) and differential thermal analysis (DTA).

Analysis of the characteristic thermogravimetric data (T M,W ) and the kinetic parameters (n, E a), together with the DTA results, with CuSO4·5H2O as control sample, provided evidence of the existence of coordinated water and of the nature of the anions in these hydrates.

The results are confirmed by the observation of a real compensation effect. For the compensation effect, the following equation is proposed: InA=0.220E-0.8

Structures explaining the presence of the coordinated water and the nature of the anions in these hydrates are also proposed.


Mittels nichtisothermer Methoden der Thermogravimetrie (TG), Derivationsthermogravimetrie (DTG) und Differentialthermoanalyse (DTA) wurde die Art des Kristallwassers in den Verbindungen MgSO4·7H2O, Mg(NO3)2·6H2O und MgCl2·6H2O untersucht. Eine Analyse der charakteristischen thermogravimetrischen Angaben (T M,W ) und der kinetischen Parameter (n, E a) zusammen mit den DTA-Ergebnissen (mit CuSO4·5H2O) als Referenzprobe) lieferten den Beweis für die Existenz koordinierten Wassers und für die Art der Anionen in diesen Hydraten.

Die Ergebnisse wurden durch die Beobachtung eines tatsächlichen Kompensationseffektes bestätigt. Für den Kompensationseffekt wird nachstehende Gleichung empfohlen: lnA=0.220E-0.8. Weiterhin wurden Strukturen vorgeschlagen, welche die Gegenwart von koordiniertem Wasser und die Natur der Anionen in diesen Hydraten erklären.

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Odochian, L. Study of the nature of the crystallization water in some magnesium hydrates by thermal methods. Journal of Thermal Analysis 45, 1437–1448 (1995).

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  • crystallization water
  • DSC
  • kinetics
  • magnesium hydrates