Premium
Hydration of Sodium β‐ and β′′‐Aluminas
Author(s) -
DUDNEY NANCY J.,
BATES J. B.
Publication year - 1987
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1987.tb05633.x
Subject(s) - sodium , enthalpy , chemistry , exothermic reaction , absorbance , water vapor , saturation (graph theory) , analytical chemistry (journal) , inorganic chemistry , phase (matter) , thermodynamics , chromatography , organic chemistry , physics , mathematics , combinatorics
The enthalpy and entropy for the hydration of sodium β ‐ and β ′′‐aluminas have been determined by measuring the infrared absorbance of single‐crystal samples following equilibration at elevated temperatures in water vapor pressures ranging from 3 to 70 kPa. The equilibrium water concentrations can be varied continuously and reversibly up to saturation concentrations of about 0.9H 2 O‐Na 1.2 AI 11 O 17.1 for the β‐phase and 0.4H 2 O.Na 1.67 Mg .67 Al 10.33 O 17 for the β′′‐phase. The hydration reactions are exothermic; Δ H =−56 ± 2 for sodium β ′′‐aIumina and ΔH =−67 ± 2 kJ/mol for sodium β‐alumina. The entropies of hydration are about −143 ± 6 J/(mol‐K) for both sodium β ‐ and β ′′‐aIuminas.