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A preliminary study of the O17 NMR spectra of aqueous solutions has shown that it is possible to distinguish solvent water from water in the hydration sphere of certain cations. For certain ions the hydration water of which is sufficiently nonlabile (lifetime for exchange >10—4 sec), it is possible to display the hydration water as a separate NMR peak when the solvent peak is shifted by addition of a paramagnetic ion. A method is suggested for determining the hydration number of such cations by measuring the change in the water available to interact with the paramagnetic ions due to water retained in the hydration sphere of the cations. The enrichment level of the O17 at present available does not permit precise determination of the hydration number, but the results are not incompatible with reasonable values.

Paramagnetic and diamagnetic shifts of the O17 NMR signal in aqueous solutions of the rare-earth ions at room temperature have been observed. The shift arises from the isotropic part of the hyperfine interaction between the O17 nucleus and the thermal average value of the spin of the rare-earth ion. The direction of the shift is in all cases opposed to the spin magnetization of the rare-earth ion. This result is explained through the formation of covalent bonds in the hydrated ion involving the rare-earth 6s orbital.

Quadrupole splitting of the deuteron magnetic resonance was measured in single crystals of solid D2O at —10°C. For deuterons on the hexagonal crystal axis, eQq1/h equaled 213.2±0.8 kc/sec, and | η1 | was equal to 0.100±0.002. For the other deuterons, eQq2/h was found to be equal to 216.4±1.0 kc/sec. No change in the line separations was observed at a temperature of —70°C. No evidence was found for hindered rotation of the D2O molecules nor for intermolecular deuteron transfer at —10°C. Lower limits to the barriers hindering these motions were estimated; these limits permit estimates to be made of hydrogen-bond energies. The coupling constants in the solid are about 30% less than those reported for the free molecule. Most of this decrease must be ascribed to electronic structural changes brought about as a result of hydrogen-bond formation.

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