Thermodynamic Properties of Rare Earth Complexes. XV. Enthalpy and Heat Capacity Changes for the Formation of Rare Earth EDTA Complexes from MgEDTA2- at 10, 20, 30 and 40 degrees C.

Heats of dilution of some aqueous rare earth electrolyte solutions at 25.degree.C. 2. Rare earth nitrates

“…A number of other anions form complexes with properties similar to the rare earth nitrates. The rare earth sulfate, EDTA, and thiodiacetate complexes (3,5,10,15) exhibit extrema for the stability constants and/or heats of dissociation of these complexes across the rare earth series. These complexes of the rare earth ions might be expected to show similar series trends in the heats of dilution at low concentrations.…”

“…The experimental technique used for solubility measurements is essentially the same as that used by Rigby (10) and Benson (2). Figure 1 presents a schematic diagram of the apparatus.…”

“…If samples of the hydrated crystals are dissolved in water to form a solution, cf = n'[0L(m2) -L•] = ' ,2 (10) where Lis the heat of solution to form an infinitely dilute solution per mole of salt, cf is the heat of solution of the sample and the other symbols have the same meaning as above. If a second sample is added to the first solution, cf + cf' = (rí + n")[0L(m3) -L•] = (rí + ") ,3 (11) where cf' is this second heat of solution.…”

Thermodynamics of aqueous EDTA systems: apparent and partial molar heat capacities and volumes of aqueous cadmium, mercury, and lead EDTA complexes

“…The standard-state heat capacities are all influenced by the same factors as the standard-state volumes, with additional contributions from relaxation effects due to the change in the distribution of structures with changes in temperature, as discussed by Ots. 43 It is evident that the standard-state volumes and heat capacities are not sensitive to direct size-charge effects of the metal cation but rather to induced structural and coordinational changes of the EDTA molecule.…”

The lanthanide ions as structural probes in biological and model systems

“…Spectrophotometric (66, 87--90), heat capacity (91,92), polarographic (93), lsO exchange (9~), and NMR (95,96) data provide convincing evidence that early in the RE series the EDTA complex exists predominantly as Ln(EDTA) (H20)x and as Ln(EDTA) (H20)v toward the end with x--y = 1 ; for ions in the middle of the series, e.g., Eu +a, both are present simultaneously. Equilibrium (6) is also believed to be important for the Ln (diglycolate)~ species (81,97).…”