Dissociation constants of oxalic acid in aqueous sodium chloride and sodium trifluoromethanesulfonate media to 175 C

Journal Article · Fri May 01 04:00:00 EDT 1998 · Journal of Chemical and Engineering Data

DOI:https://doi.org/10.1021/je970195z· OSTI ID:624357

Kettler, R M ^[1]; Wesolowski, D J; Palmer, D A ^[2]

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1. Univ. of Nebraska, Lincoln, NE (United States). Dept. of Geology
2. Oak Ridge National Lab., TN (United States). Chemical and Analytical Sciences Div.

Ethanedioic acid (oxalic acid) is ubiquitous in soils where its concentration is buffered by the presence of the minerals. Because of its ability to form strong complexes with metals, oxalic acid is used to decontaminate the cooling circuits of water-cooled nuclear reactors. The first and second molal dissociation constants of oxalic acid were measured potentiometrically in a concentration cell fitted with hydrogen electrodes. Measurements were made at six temperatures ranging from 5 C to 125 C at four ionic strengths ranging from 0.1 mol/kg to 1.0 mol/kg (NaCl and NaCF{sub 3}SO{sub 3}). The second molal dissociation constant was measured in NaCF{sub 3}SO{sub 3} media only. The data obtained in this study were combined with the corresponding literature values, including a number of recalculated Harned cell and concentration cell measurements and previous results form this laboratory. Data for first molal dissociation constant obtained in the two ionic media were regressed simultaneously to yield a five-term equation that describes the dissociation in the anionic form. The thermodynamic properties obtained at 25 C and infinite dilution are: log K{sub 1a}{sup {circle_minus}} = {minus}1.401 {+-} 0.052, {Delta}H{sub 1a} = ({minus}0.7 {+-} 0.7) kJ/mol, {Delta}S{sub 1a} = ({minus}29 {+-} 2) J/K mol, and {Delta}C{sub p,1a} = ({minus}231 {+-} 6) J/K mol. Similar treatment of the original and recalculated data for the second molal dissociation constant yielded a nine-term equation and the following values at 25 C and infinite dilution: log K{sub 2a}{sup {circle_minus}} = {minus}4.264 {+-} 0.014, {Delta}H{sub 2a} = ({minus}7.3 {+-} 0.5) kJ/mol, {Delta}S{sub 2a} = ({minus}106 {+-} 2) J/K mol, and {Delta}C{sub p,2a} = ({minus}229 {+-} 27) J/K mol.

• Sponsoring Organization: USDOE, Washington, DC (United States); National Science Foundation, Washington, DC (United States); Nebraska Univ., Lincoln, NE (United States)
• DOE Contract Number: AC05-96OR22464
• OSTI ID: 624357
• Journal Information: Journal of Chemical and Engineering Data, Journal Name: Journal of Chemical and Engineering Data Journal Issue: 3 Vol. 43; ISSN 0021-9568; ISSN JCEAAX
• Country of Publication: United States
• Language: English

Related Subjects

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS
40 CHEMISTRY
54 ENVIRONMENTAL SCIENCES
COOLANT CLEANUP SYSTEMS
DISSOCIATION
ENVIRONMENTAL TRANSPORT
FLUORINATED ALIPHATIC HYDROCARBONS
OXALIC ACID
SODIUM CHLORIDES
SODIUM COMPOUNDS
SULFONATES
THERMODYNAMIC PROPERTIES