J.W. Roddy

Mechanism of the slow extraction of iron(III) from acid perchlorate solutions by di(2-ethylhexyl)phosphoric acid in n-octane☆

Abstract The rate of iron(III) extraction by di(2-ethylhexyl)phosphoric acid (HDEHP, HA) in n-octane from acid perchlorate solutions, as FeA3. 3HA, is controlled by series and parallel reactions in the introduction of the first and second anion ligands, all occurring at the interface. (In the following subscripts, 1 and 2 refer to first and second anion ligands, m to extractant monomer, d and df to extractant dimer, s to interface saturation.) The measured rate [Fe] , r  −d[ Fe ] [ Fe ] dt , is well fitted by the step rates (25°C) r 1m = 5·5 × 10 −4 [∑HA] 0·5 /[H + ] r 1d = 1·8 × 10 −3 [∑HA]/[H + ] for parallel reactions introducing the first anion ligand, in series with r 2 ≈ 4 × 10 −4 /[H + ] 2 r 2s = 1·5 × 10 −7 /[H + ] [Fe] r 2d = 9·0 × 10 −6 [∑HA] 1·5 /[H + ] 2 r 2df = 1·2 × 10 −5 [∑HA] 2 /[H + ] 2 for parallel reactions introducting the second anion ligand. Step 2s is zero order, while all the other steps are first order, with respect to the aqueous iron concentration. In extractions through a quiescent interface these step rates combine so that r = (r 1m + r 1d ) (r 2s + r 2d + r 2df )/∑r i and in extractions with dispersion mixing so that r = (r 1m + r 1d ) r 2 / (r 1m + r 1d + r 2 ) . The rate decreases slightly with increasing ionic strength, increases with increasing temperature (heat of activation ≈ 10–15 kcal/mole) and with conditions that increase the ionization of HA, and increases sometimes markedly with addition of proton-accepting complexers that can bypass the interface steps 1m and 1d with analogous reactions homogeneous in the aqueous phase.

Activities and interaction in the Tri-n-butyl phosphate-water system

Abstract The solubility of water in TBP at 25°C and various water activities was measured by the isopiestic vapour balancing technique. The solubility follows Henrys law, XH2O = (0·478 ± 0·002)aH2O up to XH2O = 0·36 (CH2O = 1·2 M) at aH2O = 0·75, then deviates gradually at higher concentrations up to XH2O = 0·511 (CH2O = 3·58 ± 0·02 M) at saturation. The corresponding activities of TBP were calculated via the Gibbs-Duhem relation, and from these, the partial molal free energies of mixing. The activity coefficients of TBP are close to unity throughout, the greatest deviation being at water saturation: fTBP = 1·054 (mole fraction scale). Densities and thence partial molal volumes, as a function of the molality of water in TBP, were determined at both 25°C, V H 2 O = (17·08 ± 0·05) + (0·422 ± 0·04)m 1 2 and V TBP = 273·8 and 2°C, V H 2 O = (16·69 ± 0·03) + (0·526 ± 0·03)m 1 2 and V TBP = 268·3 n 1/ mole . The densities and excess partial free energies and also dielectric constants of the TBP·H2O mixtures were examined for evidence of compound formation. The former did not show any such evidence. Dielectric constants at 2°C showed a slight interaction at mole ratio 1:1, indicating that a TBP·H2O complex does exist but is only weakly bonded.

Interactions in the tri-n-butyl phosphate-water-diluent system☆

Abstract Tritium tracer techniques have been used to measure the solubility of water in undiluted TBP from 0 to 65°C at unit water activity and as a function of water activity at 25°C; from the latter results, the activity of the solvent has been derived by applying the Gibbs-Duhem relation. The solubility measurements were extended to include TBP- n -octane solutions that were 0.01-1.0 M in TBP, and these values were used to estimate hydration quotients. The solubility of water in undiluted TBP is 3.57 ± 0.02 M at 25°C and decreases slowly with increasing temperature. At constant temperature, the water content decreases rapidly at first and then more slowly with decreasing water activity. The variation of the activity of TBP in the diluent-free water system suggests that the extracted species is TBP·H 2 O, when the loading of TBP is less than 0.5 mole H 2 O per mole of TBP. Results of computer analyses of the solution data can be interpreted in terms of monomeric anhydrous TBP and the formation of the monohydrate TBP·H 2 O, and suggest the additional hydrate species (TBP·H 2 O) 2 , (TBP·H 2 O) 4 , and TBP·2H 2 O, with formation concentration quotients log Q TH = −0.82, log Q (TH) 2 = 1.82, log Q (TH) 4 = −0.39, log Q TH 2 = −1.66.

The extraction of water by tri-n-octylamine and several of its salts in benzene and phenylcyclohexane

Abstract The variation in water content of tri-n-octylamine (TOA) and several of its salts with water vapor pressure was determined by isopiestic and liquid-liquid equilibrium. In addition, the type of bonding was investigated with infrared absorption. Water was determined by Karl Fischer titration, by weight gain, and by use of titrated water as an analytical tracer. Benzene solutions of TOA extract water to form the monohydrate, with no indication of the formation of a dimer hydrate even at 0·5 M TOA. The value obtained for the equilibrium quotient with its standard error of fitting is 0·858 ± (σ = 0·006). At a fixed amine concentration, the water extracted by TOA bisulfate (TOAHS) varied nearly linearly with water activity up to aw = 0·9. That extracted by the normal sulfate (TOAS) and mixed TOA-TOAS also varied linearly with aw up to 0·4–0·7, then increased more steeply. The effect of hydration at saturation (aw = 1) depended on the amine salt form and concentration. There was little difference between benzene and phenylcyclohexane as diluents. In undiluted TOAS, water molarity varied linearly with aw up to aw = 0·7), but the mole fraction of water did not follow Henrys law above aw = 0·2). In this binary system, both TOAS and H2O showed negative deviations from Raoults law. Infrared absorption spectra suggest both hydrogen bonding of water to the anion and simple dissolution of unbonded water, but indicate no direct interaction between the oxygen of the water and the alkylammonium ion. Benzene solutions of other TOA salts tested extract less water than solutions of TOAS, Cl > NO3 > ClO4 > OAc. They follow Henrys law, from aw = 0 to 0·85 for the nitrate and to aw = 1 for the others.

Reference solutes for isopiestic and dynamic vapor pressure osmometry in organic solvents: Triphenylmethane, azobenzene, and benzil in dry benzene☆

Abstract The vapor pressure lowering of benzene solutions of azobenzene (AZO), triphenylmethane (TPM), and benzil (BZL) was measured at 20°C by two methods, one a direct differential measurement of the difference between vapor pressures of solution and solvent, and the other a direct measurement of the total vapor pressure of the solution. The results were cross-checked by isopiestic measurements at 25°C on the three pairs of benzene solutions, AZOTPM, AZOBZL, and TPMBZL. Each solute-benzene system shows some deviation from ideality. The osmotic coefficients are well-fitted by φ TPM = 0·9847−0·1120m TPM +0·00077 (m TPM +0·0504 φ AZO = 0·8795−0·0530m AZO +0·0520 (m AZO +0·4313 φ BZL = 0·7713−0·0112m BZL +0·1200 (m BZL +0·5247 The non-ideality of these solutions is not accounted for by regular solution theory, and only partially by assumption of association. With TPM (but not with AZO or BZL) it is well-accounted for by Guggenheims lattice model.

Americium metallides: AmAs, AmSb, AmBi, Am3Se4, and AmSe2

The crystal structures of several americium metallides were determined using the long-lived americium-243 isotope. Three of the binary systems produced alloys near the equiatomic compositions (AmAs, AmSb and AmBi), which were found to have the NaCl-type structure. Two compounds were identified in the AmSe system: (1) Am3Se4, which was found to have a bcc structure and (2) AmSe2 (less certain), with a tetragonal structure. The lattice parameters, calculated and observed d-spacings, and calculated and observed line intensities for these compounds are reported.

Investigation of intermolecular association of 4-sec-butyl-2-(α-methylbenzyl)phenol (BAMBP) by use of dielectric and isopiestic measurements☆

Abstract The association of the cesium extractant 4-sec-butyl-2-(α-methylbenzyl)phenol (BAMBP) in n-hexane was investigated by means of dielectric constant, density, refractive index and viscosity measurements at concentrations up to 6·85m and isopiestic measurements up to 8·8m, 25°C. The results indicate the formation of definite aggregates whose resultant dipole moments show little interaction. The osmotic data, summarized by an empirical equation for the osmotic coefficient, F = 0·28304 − 0·002075m + 0·20645/(m + 0·2880), are well matched by an aggregation model involving monomer-dimer-tetramer-pentamer, with formation concentration quotients log Q1,2 = 0·46, log Q1,4 = 1·89, log Q1,5 = 2·01. The osmotic data are alternatively fitted (ignoring the aggregation) by stoichiometric activity coefficients calculated from the osmotic coefficients, log γ = 0·08966/(m + 0·2880) − 0·71696 log(m + 0·2880) − 0·00180m − 0·6990.