Thermodynamic properties of magnesium phosphate (Mg[sub 3]P[sub 2]O[sub 8]) -- Correction of data in recent compilations

Journal Article · Sun Jan 01 04:00:00 EST 1995 · Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States)

OSTI ID:6584982

Pandit, S S; Jacob, K T ^[1]

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1. Indian Inst. of Science, Bangalore (India). Dept. of Metallurgy

Magnesium phosphates are important constituents of slags encountered in pyrometallurgy and fossil fuel combustion. To compute activities in complex slags, it is important to have accurate data for the pure compounds in the solid and liquid states. The thermodynamic data on magnesium phosphate (Mg[sub 3]P[sub 2]O[sub 8]) given in the recent versions of the JANAF tables and the compilation of Knacke et al. Contain a significant error. The erroneous data can cause serious difficulties in the chemical equilibrium calculations relevant to high-temperature technology in general and pyrometallurgy in particular. In the 1985 version of the JANAF tables, the reference state of phosphorus at 298.15 K is the [alpha] form of white phosphorus, rather than red phosphorus (V) used as a reference in the earlier version. Although red phosphorus is the more stable form, it is less well reproducible. However, the standard enthalpy of formation of magnesium phosphate at 298.15 K was not altered to reflect this change in reference state of phosphorus. Consequently, the data for enthalpy and Gibbs energy of formation and the equilibrium constant given in the 1985 compilation of the JANAF tables are incorrect. Presented in this communication are the corrected and updated thermodynamic data for magnesium phosphate (Mg[sub 3]P[sub 2]O[sub 8]), using the measured heat capacities reported in the literature.

• OSTI ID: 6584982
• Journal Information: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States), Journal Name: Metallurgical Transactions, A (Physical Metallurgy and Materials Science); (United States) Vol. 26:1; ISSN 0360-2133; ISSN MTTABN
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360606* -- Other Materials-- Physical Properties-- (1992-)
ALKALINE EARTH METAL COMPOUNDS
CORRECTIONS
DATA
ENERGY
FORMATION FREE ENTHALPY
FREE ENTHALPY
INFORMATION
MAGNESIUM COMPOUNDS
MAGNESIUM PHOSPHATES
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES