Compilation and estimation of the thermodynamic properties of solid ortho-, meta- and pyrophosphates

I - standard molar entropies and standard molar heat capacities

for solid phosphates

A. Ait-Hou1*, T. Rais2, C. Chatillon3

1 Laboratoire des Ressources Naturelles et d’Environnement, Département de Chimie , Faculté des Sciences et Techniques, B.P.509, Boutalamine, Errachidia, Morocco

2 Département de Chimie, Faculté des Sciences casa1, Morocco

3 Laboratoire de Thermodynamique et Physico-chimie Métallurgiques, (CNRS, UMR 5614 UJF/INPG ), E.N.S.E.E.G., Domaine Universitaire, B.P.75, 38402 Saint-Martin d'Hères, France

* Corresponding author. E-mail: aithou@netcourrier.com

Received: 11 October 2003; revised version accepted: 25 August 2005

Abstract

Thermodynamic of condensed phosphates are reviewed in order to check usual models to estimate their properties. For standard molar entropies S and standard molar heat capacities C(298.15 K), the rule of additivity of oxides entropies seems the best way with an accurancy of 2% and we have used this rule to generate thermodynamic data of alkaline, alkaline-earth, transition, rare-earth and "p" metals phosphates. C(T) are calculated using the formula proposed by Kellog, but this reliability cannot be ascertained since informations about allotropic transitions are scarce.

Keywords: Thermodynamics of phosphates; Entropies; Heat capacities.

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