Health & Environmental Research Online (HERO)


Print Feedback Export to File
1773503 
Journal Article 
Heat capacities of aqueous solutions of sodium hydroxide and water ionization up to 300 degrees C at 10 MPa 
Schrodle, S; Konigsberger, E; May, PM; Hefter, G 
2008 
Yes 
Geochimica et Cosmochimica Acta
ISSN: 0016-7037 
72 
13 
3124-3138 
WOS:000257175800005 
A commercial (Setaram C80) calorimeter has been modified to measure the heat capacities of highly caustic solutions at temperatures up to 300 degrees C and pressures up to 20 MPa. The improvements have allowed more accurate determination of the isobaric volumetric heat capacities of chemically aggressive liquids at high temperatures. Test measurements with aqueous solutions of sodium chloride showed a reproducibility of about +/- 0.1%, with an accuracy of similar to 0.3% or better, over the whole temperature range. Heat capacities of aqueous solutions of sodium hydroxide at concentrations from 0.5 to 8 mol/kg were measured at temperatures from 50 to 300 degrees C and a pressure of 10 MPa. Apparent molar isobaric heat capacities of NaOH(aq) were calculated using densities determined previously for the same solutions by vibrating-tube densimetry. Standard state (infinite dilution) partial molar isobaric heat capacities of NaOH(aq) were obtained by extrapolation using an extended Redlich-Meyer equation. Values of the standard heat capacity change for the ionization of water up to 300 degrees C were derived by combining the present results with the literature data for HCl(aq) and NaCl(aq). (c) 2008 Elsevier Ltd. All rights reserved. 
thermodynamic properties; heat capacity; sodium hydroxide; aqueous solutions; water ionization; high temperature