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ECN publication
Title:
Determination of structural, thermodynamic and phase properties in the NA2S-H2O system for application in a chemical heat pump
 
Author(s):
 
Published by: Publication date:
ECN Energy Efficiency in Industry 1-3-2002
 
ECN report number: Document type:
ECN-RX--02-009 Article (scientific)
 
Number of pages:
32  

Published in: The paper is to be published in: Thermochimica Acta (Jan. 3003) (), , , Vol., p.-.

Abstract:
Structural, thermodynamic and phase properties in the Na2S-H2O systemfor application in a chemical heat pump have been investigated using XRD, TG/DTA and melting point and vapour pressure determinations. Apart from the known crystalline phases Na2S-9H2O, Na2S-5H2O and Na2S a new phase Na2S-2H2O has been proven to exist. Na2S-½H2O is not a phase but a 3:1 mixture of Na2S and Na2S-2H2O, presumably stabilised by very slow dehydration kinetics. The vapour pressure-temperature equilibria of the sodium sulphide hydrates have been determined and a consistent set of thermodynamic functions for these compounds has been derived. XRD measurements indicate the topotactic character of the transitions between the hydration states.


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