Thermodynamics of the complexes of aqueous iron(III), aluminum, and several divalent cations with EDTA: heat capacities, volumes, and variations in stability in temperature

Journal Article · Thu Dec 05 04:00:00 EST 1985 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100271a047· OSTI ID:5896295

Hovey, J K; Tremaine, P R

Apparent molar heat capacities and volumes at 25 /sup 0/C have been determined for aqueous H/sub 2/EDTA/sup 2 -/ and for the complexes of aqueous EDTA/sup 4 -/ with Ca/sup 2 +/, Mg/sup 2 +/, Al/sup 3 +/, Fe/sup 3 +/, Mn/sup 2 +/, Co/sup 2 +/, Ni/sup 2 +/, Cu/sup 2 +/, and Zn/sup 2 +/, all as the sodium salts. The standard-state partial molar heat capacities, anti C/sub p//sup 0/, and volumes, anti V/sup 0/, derived from these measurements were treated by using the simple Born model to calculate the coulombic effects on the surrounding water. The non-Coulombic contributions to anti C/sub p//sup 0/ and anti V/sup 0/ are very similar for all the complexes, and small systematic variations are consistent with known structures of the aqueous complexes. Values for the partial molar properties anti C/sub p/ and anti V were combined with critically evaluated literature data to calculate the temperature dependence of the stability constants at 0.1 m ionic strength. The relative stability of the complex ions MgEDTA/sup 2 -/(aq), FeEDTA/sup -/(aq), and AlEDTA/sup -/(aq) increase sharply relative to CaEDTA/sup 2 -/(aq) and the complexes with other M/sup 2 +/ ions. 58 references, 6 figures, 7 tables.

• Research Organization: Alberta Research Council, Edmonton
• OSTI ID: 5896295
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 89:25; ISSN JPCHA
• Country of Publication: United States
• Language: English

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ALKALINE EARTH METAL COMPLEXES
ALUMINIUM COMPLEXES
AMINO ACIDS
CALCIUM COMPLEXES
CARBOXYLIC ACIDS
CHELATING AGENTS
COBALT COMPLEXES
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COPPER COMPLEXES
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MAGNESIUM COMPLEXES
MANGANESE COMPLEXES
NICKEL COMPLEXES
NUMERICAL DATA
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
SPECIFIC HEAT
STRUCTURAL CHEMICAL ANALYSIS
TEMPERATURE DEPENDENCE
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPLEXES
VOLUME
ZINC COMPLEXES