SOME PROPERTIES OF RARE EARTH-NITRILOTRIACETATE COMPLEXES

Journal Article · Wed Aug 01 04:00:00 EDT 1962 · Dissertation Abstr.

OSTI ID:4778221

Levy, S C

The stability constants of the 1:1 and 1: 2 rare earthnitrilotriacetate complexes were measured polarographically at 10, 20, 30, and 40 deg C at an ionic strength of 0.10. The stability constants of the 1: 1 complexes increased with increasing atomic number of the rare earth through samarium, decreased at europium and gandollnium, and then increased linearly through lutetium. The stability of the 1: 2 rare earth-NTA complexes increased from lanthanum through terbium, decreased from dysprosium through thulium, and showed a slight increase at ytterbium and lutetium. The stability of the yttrium chelate was nearest that of the terbium chelate in the 1: 1 complex and closest to the samarium chelate in the 1:2 complex. The so-called gadolinium break was evident in both series or constants. The measured constants correctly predicted the extent of separation of the entire rare earth series and also the position of yttrium in the ion- exchange separation of the rare earths using NTA as eluant. The thermodynamic functions DELTA F deg , DELTA H deg , and DELTA S deg were calculated for both sets of compounds from the temperature dependence of the stability constants. A positive enthalpy change was found for the series of 1: 1 complexes and a negative enthalpy change for the series of 1:2 complexes. In both series of compounds, it was found that the main driving force for chelation was a favorable entropy change. The solid 1: 1 rare earth-NTA chelates were prepared at different temperatures and analyzed. The hydrates found for the various species ranged from mono to pentahydra-tes. There seemed to be no order in the lightest members of the series, where almost every hydrate was found. The middle members of the series formed only the trihydrate and the heavier members each formed a dihydrate and a tetrahydrate. The solubility of each hydrate of the 1: 1 rare earth-NTA chelates was measured at 25 and 60 deg C.

• Research Organization: Iowa State Univ. of Science and Tech., Ames
• NSA Number: NSA-16-032977
• OSTI ID: 4778221
• Journal Information: Dissertation Abstr., Journal Name: Dissertation Abstr. Vol. Vol: 23
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ACETATES
ATOMS
CHELATES
CHEMISTRY
COMPLEXES
DIAGRAMS
ELECTRIC CHARGES
ENTHALPY
ENTROPY
ION EXCHANGE
NUMERICALS
ORGANIC NITROGEN COMPOUNDS
POLAROGRAPHY
RARE EARTHS
SOLUBILITY
STABILITY
TEMPERATURE
THERMODYNAMICS