A STUDY OF THE RARE-EARTH METAL COMPLEXES

Journal Article · Tue May 01 04:00:00 EDT 1962 · Dissertation Abstr.

OSTI ID:4827593

Kolat, R S

The solid rare-earth chelates of ethylenediaminetetraacetic acid were examined using thermobalance, infrared and x-ray-diffraction techniques. The lighter members are monohydrates while the heavier members are anhydrous after drying for 12 hours at 110 deg C. Infrared studies indicated that the light- member chelates have a pentadentate EDTA structure while the remaining rare earths assume a hexadentate configuration. The transition occurs with europium. X-ray-diffraction studies substantiated this structural change. Ionization constant determinations of these acids indicated that a corresponding change does not occur in solution. Examination of the alkali metal salts of these acids indicated that these rare-earth compounds are probably mutually isomorphous. The complex formation constants of the rare earths with the acetate, methoxyacetate, thioglycolate and alpha -hydroxyisobutyrate ligands were determined at 20 deg C. An ionic strength of 0.10 was used in the solutions with sodium perchlorate as the supporting electrolyte. A glass electrode was used for the potentiometric determination of the hydrogen ion concentrations. The acetate constants were found to be ln an inverted order from that predicted by ionic radii considerations. The heavier m~mbers of the rare-earth series had lower complex formation constants than the lighter members. Similar trends were noted with the methoxyacetate and thioglycolate ligands. The methoxy group and the sulfhydryl group contribute little if any to chelate formation with the rare-earth ions. The values of the first complex formation constant of these ligands with the rare earths are all in the range of 100 to 200 at an ionic strength of 0.10. The alpha -hydroxyisobutyrate anion formed quite stable complexes with the trivalent rare-earth ions. The formation constants found were greater than the corresponding constants of the glycolate and lactate ligands. The increase in stability is attributed to the inductive effect of the methyl group. The magnitude of the observed constants supported the postulation of a bidentate chelating action of these ligands on the rare earths. The differences in the magnitudes of the individual constants for the various rare earths confirmed previously reported data which showed that alpha -hydroxyisobutyric acid was an exceptionally good eluting agent for the rare earths in ion exchange systems.

• Research Organization: Iowa State Univ. of Science and Tech., Ames
• NSA Number: NSA-16-022097
• OSTI ID: 4827593
• Journal Information: Dissertation Abstr., Journal Name: Dissertation Abstr. Vol. Vol: 22
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

CHEMISTRY