Thermodynamic properties of the ionization of morpholine as a function of temperature and ionic strength

Journal Article · Thu Jun 01 04:00:00 EDT 2000 · Journal of Chemical and Engineering Data

DOI:https://doi.org/10.1021/je9903146· OSTI ID:20076020

Ridley, M K; Xiao, C; Palmer, D A; Wesolowski, D J

Morpholine, O(C{sub 2}H{sub 4}){sub 2}(NH), is widely used in many industrial applications as a pH buffering agent and corrosion inhibitor; in particular, it is utilized at elevated temperatures in nuclear power plants. A hydrogen-electrode concentration cell was used to monitor pH in a study of morpholine ionization in aqueous solutions to temperatures of 290 C and to ionic strengths of 1 m, maintained with either sodium trifluoromethanesulfonate or sodium chloride. The resulting hydrolysis quotients were combined with values from two previous potentiometric investigations of this reaction, as well as existing heat capacity and apparent molar volume data, to provide a global fitting equation. The computed thermodynamic parameters for the acid dissociation of the morpholinium ion at 25 C and infinite dilution are log K = ({minus}8.491 {+-} 0.003); {Delta}H = (39 {+-} 1) kJ/mol; {Delta}S = ({minus}31 {+-} 1) J/K{center_dot}mol; {Delta}C{sub p} = (40 {+-} 7) J/K{center_dot}mol; and {Delta}V = (3 {+-} 1) cm{sup 3}/mol. At low ionic strengths, including values at infinite dilution, the log Q data were found to be near linear with respect to the reciprocal temperature in Kelvin over the measured temperature range of 0 C to 300 C.

• Research Organization: Texas Tech Univ., Lubbock, TX (US)
• Sponsoring Organization: US Department of Energy; Electric Power Research Institute
• OSTI ID: 20076020
• Journal Information: Journal of Chemical and Engineering Data, Journal Name: Journal of Chemical and Engineering Data Journal Issue: 3 Vol. 45; ISSN JCEAAX; ISSN 0021-9568
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
36 MATERIALS SCIENCE
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
CORROSION INHIBITORS
IONIC CONDUCTIVITY
IONIZATION
MORPHOLINES
NUCLEAR POWER PLANTS
PH VALUE
THERMODYNAMIC PROPERTIES
WATER CHEMISTRY