THERMODYNAMIC STUDY OF THE SOLID-LIQUID EQUILIBRIA

IN THE MIPO3-Pb(PO3)2 SYSTEMS (MI = Li, Na, K)

C. Marhag1,*, D. Ben Hassen-Chehimi2, C. Favotto3, H. SAID1

1 Laboratoire de Thermodynamique, Faculté des Sciences de Bizerte, 7021-Zarzouna-Bizerte, Tunisia

2 Laboratoire de Physico-Chimie Minérale, Faculté des Sciences de Bizerte, 7021-Zarzouna-Bizerte, Tunisia

3 Laboratoire de PhysicoChimie du Matériau et du Milieu Marin, Faculté des Sciences et techniques,

Université de Toulon-Var, France

* Corresponding author. E-mail : merhagg@yahoo.fr

Received : 14 December 2002; revised version accepted : 04 February 2003

Abstract

Thermodynamic exploitation of solid-liquid equilibrium of the MIPO3-Pb(PO3)2 (with MI = Li, Na, K) systems is carried out using a semi-empirical equation of the liquidus curves of a stoïchiometric phase already used with success for similar binary systems.

The temperature, enthalpy and entropy of fusion are calculated for each solid phase. The enthalpy of fusion of pure polyphosphates and the intermediate compounds was determined from the DTA curves. The calculated values of the melting enthalpy of these polyphosphates are approximately equal to the measured ones.

The calculated temperatures and compositions in most binary systems are in good agreement with experimental determinations.

Keywords : Phase diagram; Thermodynamic exploitation; Binary system; Polyphosphates; Enthalpy.

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