Solubility product values of the rare earth fluorides were determined potentiometrically by using fluoride ion-selective electrodes at 25.0 °C. The pKsp values of the lanthanoid fluorides decreased gradually from 20.0 to 16.9, while the value for yttrium fluoride was locate in between those of terbium and dysprosium fluorides. The value for scandium fluoride was appreciably smaller than any of the lanthanoid fluorides, as expected from the cationic radii. The solubility product value of lanthanum fluoride single crystal could not be determined, since the saturated solution was not obtained through measurements of over three months.

A 49-year-old female with no history of hearing disturbance developed sudden onset of headache and was admitted with no neurological deficits other than mild nuchal rigidity. Computed tomography (CT) showed subarachnoid hemorrhage. Four-vessel cerebral angiography disclosed no aneurysm. A second angiogram obtained on the 14th day showed vasospasm of the bilateral posterior cerebral arteries and right anterior inferior cerebellar artery, but still failed to demonstrate an aneurysm. Following the second angiography, she developed mild disturbance of consciousness and cerebellar ataxia of the right limbs, and repeat CT showed an infarct in the right cerebellar hemisphere. When she regained consciousness a few days later, she was completely deaf on the right side. The third angiography revealed a right vertebral artery dissecting aneurysm. Following clipping of the proximal portion of the right vertebral artery, she did well and was discharged, although right cerebellar ataxia and deafness persisted. Neuro-otological evaluation, including pure-tone audiography, auditory brainstem responses, electrocochleography, and caloric testing, indicated that her deafness resulted from ischemia in the territory of the right internal auditory artery due to vasospasm.

The stability constants of scandium complexes with some carboxylate ligands were determined potentiometrically at 25.0 and 40.0 °C and at an ionic strength of 0.10 with potassium nitrate as supporting electrolyte. The constants of the scandium complexes were appreciably greater than those of the corresponding lanthanoid complexes, as expected. The changes in free energy, enthalpy, and entropy for the formation of the scandium complexes were calculated from the stability constants at two temperatures.

The stability constants of scandium complexes with malonate, maleate, itaconate, glutarate, adipate, and succinate ligands were determined titrimetrically at 25.0 °C and at an ionic strength of 0.1. The chelate effect was negligible for the stability of the scandium complexes with the dicarboxylate ligands studied in contrast with the lanthanoid complexes. The complex formation of scandium might be explained by an electrostatic ionic bond similar to ones exhibited in the lighter rare-earth complexes, due to linear relationships between the stability constants and the ionic potential Z2⁄r.

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