J. S. Drury

Lithium isotope separation factors of some two-phase equilibrium systems

Isotope separation factors of seventeen two‐phase equilibrium systems for lithium isotope enrichment have been determined. In all cases, lithium amalgam was used as one of the lithium‐containing phases and was equilibrated with an aqueous or organic phase containing a lithium compound. In all systems examined, isotopic exchange was found to be extremely rapid, and 6Li was concentrated in the amalgam phase. The isotopic separation factor for the LiOH(aqueous) vs Li(amalgam) system has been studied as a function of temperature from −2 to 80 °C. The values obtained have been compared with the ’’electrolysis’’ and exchange separation factors given in the literature. The two‐phase systems, LiCl(ethylenediamine) vs Li(amalgam) and LiCl(propylenediamine) vs Li(amalgam), have been studied, and the isotopic separation factors have been determined as functions of the temperature. The factors for the two systems have been found to be substantially the same (within limits of the errors involved) over the temperature ...

Nitrogen‐Isotope Effects in the Reduction of Nitrate, Nitrite, and Hydroxylamine to Ammonia. I. In Sodium Hydroxide Solution with Fe (II)

Studies were made of the nitrogen‐isotope effects occurring during the alkaline reduction of NO3−, NO2−, and NH2OH with Fe(II). The pertinent reduction reactions were shown to be irreversible and the yields of NH3 quantitative. The reduction of NO3− to NH3 produced a k14/k15 value of 1.075±0.004 at 25°C. A k14/k15 ratio of 1.034±0.002 at 25°C was obtained for the reduction of NO2−, or NH2OH to NH3. The rate constant, kNO3−, was shown to be slow compared to kNO2− and kNH2OH which had values of 4.09×10−2 and 9.53×10−3 sec−1, respectively.The experimental data agreed well with results computed for a two‐atom model in which the significant step in the reduction of each species was the breaking of an N–O bond. Reactions consistent with the experimental data were proposed to account for the reduction mechanism.

SEPARATION OF CALCIUM ISOTOPES IN AN AMALGAM SYSTEM

Concentration of the heavy isotopes of calcium by means of the chemical exchange reaction 46Ca(Hg)+40Ca++(solution)=40Ca(Hg)+46Ca++(solution) was studied. The reaction was found to be technically feasible as a pre‐enriching process for Calutron feed material; its economic attractiveness depends upon a sufficiently large scale of application. At 25°C, the single‐stage separation factor for isotopes differing by one unit of mass was 1.0013±0.0003 (95% C.I.). The half‐time of exchange of calcium was less than 7 sec. The solubility of calcium in mercury varied from 0.562M at 0°C to 0.908M at 36°C. The integral heat of solution of calcium in mercury was given by the least‐squares equation, —ΔH±0.2(95% C.L.)=45.43–0.56M.

Separation of Boron Isotopes. VI. Ethyl Ether, Ethyl Sulfide, and Triethylamine‐BF3 Systems

The BF3 complexes of ethyl ether, ethyl sulfide, and triethylamine were studied. Isotopic equilibrium constants for the reactions B10F3(g)+B11F3·donor(l)⇌B10F3(g)+B10F3·donor(l) were measured at several temperatures for each of the three systems. Vapor pressures of the ethyl sulfide complex, and rates of exchange of boron between BF3 and BF3·Et3N were also determined.

Separation of Boron Isotopes. V. The Phenol‐BF3 System

The exchange of boron between BF3(g) and BF3·phenol(l) was studied. The single‐stage isotopic fractionation factor varied according to the equation, logα= (10.315/T) —0.02423, over the temperature range —8°C to 37°C. B10 is concentrated in the liquid phase. Vapor‐pressure measurements of dilute and concentrated solutions of BF3 in phenol were made at various temperatures from —10°C to 40°C. The freezing point of the BF3·phenol complex was approximately —15°C; that for the BF3·2 phenol, —5°C.

Separation of Boron Isotopes. IV. The Methyl Sulfide‐BF3 System

The exchange of boron between BF3 (gas) and the dimethyl sulfide‐BF3 complex (liq.) was studied from —20°C to +26°C. The single stage separation factor changed from 1.056 to 1.031 over this temperature range with B10 concentrating in the liquid phase. Vapor pressures of dimethyl sulfide and of various mixtures of BF3 and dimethyl sulfide were determined. ΔH for the reaction BF3 (gas)+Me2S (liq.)→BF3·Me2S (liq.) was estimated to be —10.1 kcal/mole over the above temperature range. The melting point of the 1:1 complex was —19.6°C.

Separation of Boron Isotopes. VIII. BF3 Addition Compounds of Dimethyl Ether, Dimethyl Sulfide, Dimethyl Selenide, Dimethyl Telluride, Dibutyl Ether, and Ethyl Formate

Studies were made of the physical and chemical properties of molecular addition compounds formed by BF3 and Group VIb donors. The dimethyl telluride complex was too unstable to exist at temperatures above −30°C. The freezing point of the 1:1 dimethyl selenide·BF3 compound was −43°C. From room temperature to its freezing point, the saturation pressure of the 1:1 dimethyl selenide complex was given by log10 P=9.945— (1824/T). The 1:1 butyl ether and ethyl formate complexes formed at 25°C but deteriorated slowly with the formation of noncondensible gases. The freezing points of these complexes were −30° and −8°C, respectively. Between room temperature and their freezing point, the saturation pressures of freshly prepared Bu2O·BF3 and HCOOEt·BF3 were given by logP=5.65— (1010/T) and logP=5.70— (1330/T), respectively. For the same temperature range, the equilibrium constant for the isotopic exchange reaction 10BF3(g)+A·11BF3(l)=11BF3(g)+A·10BF3(l) was given by logKeq=(8.13/T) −0.0131, when A was dimethyl selen...

NITROGEN ISOTOPE EFFECTS IN THE DECOMPOSITION OF DIAZONIUM SALTS

The nitrogen isotope effects produced upon fractionally decomposing C6H5NNCl, C6H5NNBF4, m‐ClC6H4NNBF4, o‐, m‐, and p‐CH3C6H4NNBF4 were measured as a function of temperature. Between 5° and 70°C the data are well represented by the least‐squares equation, log(k14/k15)=6.949/T−0.002528. The experimental results agree well with those predicted from spectroscopic data. The data are consistent with the model in which decomposition occurs through the rupture of a single C–N bond. The observed isotope effect is insensitive to the nature and position of substituents on the aromatic ring and to the anion of the salt. The difference in the activation energy for the decomposition of the 14N‐ and 15N‐labeled diazonium salts is 32 cal mole−1·deg−1.

Isotopic Separation Factor for the System Potassium Amalgam—Aqueous Potassium Hydroxide

The isotopic fractionation of potassium between potassium amalgam and aqueous potassium hydroxide was measured at room temperature. The single‐stage separation factor was 1.006±0.002 (95% C. I.).

Nitrogen Isotope Effects in the Reduction of Nitrate, Nitrite, and Hydroxylamine to Ammonia. II. The MgO and CuSO4 Systems

Nitrogen kinetic isotope effects were used to study reaction mechanisms associated with reductions of NO3−, NO2−, and NH2OH in hot alkaline solutions that contained Fe(II). In the CuSO4 system the specific reaction rate constants varied in the order kNO2− > kNO3− > kNH2OH, rather than the order kNO2− > kNH2OH > kNO3− found previously in the Ag2SO4 system. When MgO was used, the order of the specific reaction rate constants was the same as that observed with Ag2SO4, but different mechanisms operated in the reduction of NO3− and NO2−, although not in the reduction of NH2OH. Reactions consistent with the observed isotope effects and the known chemistry of nitrogen were postulated for the most probable reaction paths in the various systems.