Date of Award

8-1987

Degree Name

Master of Science

Department

Geosciences

First Advisor

Dr. John D. Grace

Second Advisor

Dr. Robert Hunt Anderson

Access Setting

Masters Thesis-Open Access

Abstract

Stilbite is a calcium-rich zeolite found in low-grade metamorphic and hydrothermally altered environments. In this study, measurements of the enthalpy of formation at 298.15 K, heat capacity from 5 to 350 K, and enthalpy increments horn 350 to 500 K were performed on a specimen of stilbite characterized by electron microprobe analysis. The actual formula of the stilbite is: Ca1.019Na0.136K0.006Al2.180Si6.820O16 . 7.33H2O. Evaluation of the thermodynamic properties for stilbite at T = 298.15 K produced the following values: ΔrHOm(T)= -11034.6+6.6 kJ . mol-1, COp,m(T)=808.73+1.62 J.K-1, SOm(T)-SOm(0)=805.54+1.61 J.K-1.mol-1fSom(T)= -2990.44+1.86 J.K-1, mol-1, and ΔfGom(T)= -10143.0+6.6 kJ.mol-1. Comparison of the calorimetrically derived value for the Gibbs free energy of formation, ΔfGom, of stilbite with that calculated from an estimation method (La Iglesia and Anzar, 1986) shows a difference of 49 kJ.mol-1. An attem pt was made to retrieve a consistent Gibbs free energy value for laumontite using available phase equilbria and calorimetric data for heulandite and stilbite.

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Geology Commons

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