The proton magnetic resonance spectra of cation-exchange resins of crosslinkage XI to XI6 in the H +, Li', N a + , K -, R b + , Cs +, and NH,' forms have been recorded and the values of the molal chemical shift, 6, , +O, are found to be -0.321, -0.005,0.041,0.031,0.028,0.015, and 0.00 (assumed) p.p.m./mole, respectively, for the cations. These values are very nearly equal to those observed in corresponding aqueous solutions, indicating that ion-solvent interactions are similar in both the resin matrix and the aqueous solution. The temperature dependence of the chemical shift shows the same trend. The effective hydration numbers calculated from the temperature dependence are 2.0 (4.81 m ) for the H + form, 4.8 (3.25 m) and 3.6 (5.26 177) for the Na' form, 4.4 (3.9 m) for the K + form, and 2.4 (6.18 171) for the Cs+ forsn. The ions in the resin phase behave as solutions of strong electrolyte, which is consistent with the polyelectrolyte gel model for the ion-exchange resin.Canadian Journal of Chemistry, 48, 917 (1970) Introduction Nuclear magnetic resonance (n.1n.r.) has bee11 exte~lsively applied to the study of ionic solvation and three reviews (1-3) serve to indicate the extent and scope of present interest in the field. The n.m.r. studies fall into four categories: measurements of (i) reiaxation times, (ii) peak areas. under suitable, though unfortunately uncommon, conditions, solvent exchange may be slowed down sufficiently to allow the observation of cationic solvation shells, leading to a direct determination of the primary solvation number of the cation (4). In contrast, solvation numbers determined by observation of che~nical shifts in electrolyte solutions have a less obvious sigilificauce, since both cationic and anionic effects contribute to the chemical shift. Malinowski and co-workers (5-7) have performed a series of such experiments, observing the proton chemical shift of aqueous electrolyte solutions a t several temperatures and obtaining an "effective" solvation number.It is of interest to perform similar experiments on ion-exchange resin in as q~~arltitative a manner as possible, so that insight may be gained as t o the environ~iients of the ionic species within the resin.Experimental

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The proton magnetic resonance spectra of anion-exchange resin Dowex AGI of various crosslinkages ranging from X1 to XI0 in the F-, C1-, Br-, I-, NOs-, and C104-forms have been recorded and the values of the molal chemical shift, 60x-, are found to be -0.035, 0.026 (assumed), 0.035, 0.045, 0.037, and 0.058 p.p.m./mol, respectively, for the anions. These values are generally lower compared to those observed in corresponding aqueous solutions, indicating that ion-solvent interactions are similar in both the resin matrix and the aqueous solution but there is probably increased ion association in the resin phase. The effective hydration numbers have been deduced from the temperature dependence measurements of proton chemical shifts for the alkali-metal ions and for a few anions in various crosslinkages of Dowex AG 50W and Dowex AGI resins. The values of the hydration number decrease as the crosslinkage increases for the alkali-metal ions. The decrease in the hydration number at high crosslinkage is attributed to ion association in the resin phase. The reversal of selectivity in KC/CsC system below X16 in the sulfonated resin is explained on the basis of decrease in the hydration of K C form of resin compared to that of Cs+ form, consistent with the experimental observations. The electrostatic interactions between the counterion and fixed group and ions and solvent in the resin phase have been discussed in the light of the proposed models.Canadian Journal of Chemistry, 49, 457 (1971) Introduction A considerable body of experimental data has been obtained in connection with equilibria and kinetics in ion-exchange resin (1-3). Several models have been proposed to interpret and to predict the selectivity of ions when in equilibrium with their respective solutions. The model proposed by Gregor pictures the ion-exchanger as consisting of two parts, an un-crosslinked polyelectrolyte with solvent and the cross linking. Selectivity for an ion is considered to arise primarily because of differences in the partial molal volumes of the counterions in the resin phase (4). The other models rely on the electrostatic interactions between the counterion and the fixed group and the ion-solvent interactions (5-7). In all these models ion-pair formation and ionic hydration is recognized as of key importance to explain the observed swelling pressures and selectivity of ions under a variety of conditions. An excellent review has been presented by Reichenberg and Diamond and Whitney in ref. 2. However, there is very little direct experimental evidence to support or disprove the basic assumptions on which the models are based. Glueckauf and Kitt obtained the hydration numbers of cations in the resin phase by a method based on thermodynamical considerations (8).'To whom all correspondence should be addressed.Nuclear magnetic resonance (n.m.r.) has proved to be a versatile technique in studying ionic solvation in aqueous and non-aqueous solutions of electrolytes (9-1 1). More recent studies in this connection concern the determination of s...

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The radiochemical yields of molybdenum-99, ruthenium-103 and -105, palladium-109 and -112, silver-11 1 and -113, cadmium-115, and tin-121 and -125 formed in the 14 MeV fission of thorium-232 and uranium-238 have been determined using a low background Geiger-Muller counter, NaI(T1) crystal, and Ge(Li) detector. The absolute mass yield for molybdenum-99 has been obtained using a copper monitor for neutron flux and for the other nuclides using molybdenum-99 as an internal standard. The mass distribution curves derivcd from the chain yields, in the symmetric region show the presence of a third peak in thorium-232, and only the familiar two peaks for uranium-238 in the asymmetric region. By comparison of normalized cumulative mass yields from this study with prompt fission yield data, the average number of prompt neutrons emitted from fission fragments has been obtained as a function of mass in Z 3 8 U + n fission. It appears that there are two regions of enhanced neutron emission in the mass range 103-128, and that the heavy fragments emit more neutrons than the light ones.

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