Thermochemistry of natural potassium sodium calcium leonhardite and its cation-exchanged forms

Abstract

Other| June 01, 1996 Thermochemistry of natural potassium sodium calcium leonhardite and its cation-exchanged forms Irina Kiseleva; Irina Kiseleva Princeton University, Department of Geological and Geophysical Sciences, Princeton, NJ, United States Search for other works by this author on: GSW Google Scholar Alexandra Navrotsky; Alexandra Navrotsky Search for other works by this author on: GSW Google Scholar Igor A. Belitsky; Igor A. Belitsky Search for other works by this author on: GSW Google Scholar Boris A. Fursenko Boris A. Fursenko Search for other works by this author on: GSW Google Scholar American Mineralogist (1996) 81 (5-6): 668–675. https://doi.org/10.2138/am-1996-5-614 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Irina Kiseleva, Alexandra Navrotsky, Igor A. Belitsky, Boris A. Fursenko; Thermochemistry of natural potassium sodium calcium leonhardite and its cation-exchanged forms. American Mineralogist 1996;; 81 (5-6): 668–675. doi: https://doi.org/10.2138/am-1996-5-614 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Leonhardite, a partially dehydrated laumontite, and its alkali variety, primaryleonhardite, have been studied by high-temperature calorimetry. The enthalpies of formation from oxides and elements at 298 K are -306.7 ± 7.1 and -14214.6 ± 11.2 kj/mol, respectively, for leonhardite, Ca2Al4Si8O24.7H2O, and -521.2 ± 10.5 and -14253.7 ± 13.5 kj/ mol, respectively, for primary leonhardite of composition Ca1.3Na0.6K0.8Al4Si8O24.7H2O. The values for primary leonhardite are significantly more negative. New calorimetric data for sodium and potassium oxides were obtained on the basis of thermochemical cycles involving carbonates. The enthalpies of drop solution are -113.10 ± 0.83 kj/mol for Na2O and -193.68 ± 1.10 kj/mol for K2O3 giving enthalpies of solution of -170.78 ± 0.90 kj/mol for Na2O and -260.98 ± 1.20 kj/mol for K2O. The effects of exchange cations (K3Na) onenergetics and dehydration were studied using cation-exchanged samples. Alkali substitution decreases thermal stability (decomposition on heating in air) but increases thermodynamic stability with respect to the oxides and elements. Equilibrium relations between leonhardite and alkali-feldspar, calculated on the basis of these data, show that primary leonhardite can form only from geothermal solutions having rather high ratios of alkali ions to Ca. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.