Journal of thermal analysis

, Volume 38, Issue 8, pp 1793–1799 | Cite as

The effect of water vapour pressure on the thermal dehydration of yttrium formate dihydrate

  • Y. Masuda
  • Y. Ito
Article

Abstract

The kinetics of the thermal dehydration of yttrium formate dihydrate was studied by means of isothermal gravimetry under various water vapour pressures from 5×10−4 to 8 torr. On the whole, the dehydration was described as the three dimensional phase boundary reaction, R3. An unusual dependence of the rate of dehydration on the atmospheric water vapour pressure was observed: with increasing water vapour pressure, the rate increased at first, passed through a maximum, and then decreased gradually to a constant value. These phenomena were similar to the Smith-Topley effect. The mechanism of the phenomena can be described on the basis of the crystallinity of the dehydrated product phase.

Keywords

hydrated salts kinetics thermal dehydration yttrium formate dihydrate 

Zusammenfassung

Mittels isothermer Gravimetrie und bei verschiedenen Wasserdampfdrücken zwischen 5×10−4 und 8 Torr wurde die Kinetik der thermischen Dehydratation von Yttriumformiat-Dihydrat untersucht. Die Dehydratation wird als dreidimensionale Phasengrenzreaktion R3 beschrieben. Dabei wurde ein ungewöhnlicher Einfluß des athmosphärischen Wasserdampfdruckes auf die Dehydratationsgesch windigkeit beobachtet: mit steigendem Wasserdampfdruck wächst die Geschwindigkeit zunächst ebenfalls an, durchquert ein Maximum und sinkt dann nach und nach auf einen konstanten Wert ab. Diese Erscheinung ähnelt dem Smith-Topley-Effekt. Der Mechanismus dieser Erscheinung kann auf der Grundlage der Kristallinität der dehydratierten Produktephase diskutiert werden.

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Copyright information

© Wiley Heyden Ltd., Chichester and Akadémiai Kiadó, Budapest 1992

Authors and Affiliations

  • Y. Masuda
    • 2
    • 1
  • Y. Ito
    • 2
  1. 1.Department of Chemistry, College of General EducationNiigata UniversityNiigataJapan
  2. 2.Department of Chemistry, Faculty of ScienceNiigata UniversityNiigataJapan

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