Liquid Distribution Coefficients Research Articles

Liquid disoertion in packed columns—II: The Gunn model

The Gunn model is based on differing permeabilities in the bulk of the packing and a wall region. Previous results using liquid distributors with more than 1400 points/m 2 resulted in a good agreement between the Gunn model and experimental data on liquid distribution and liquid dispersion coefficients. The extensive results reported in this paper with a liquid distributor containing 70 points/m 2 show a wide divergence from the Gunn model. In addition an extensive set of results was obtained with a wall distributor again resulting in a wide divergence from the Gunn model. There is a research need to investigate the effects of liquid distributor design for a comprehensive understanding of liquid flow in packed columns.

Observations on capacity factor determination for reversed-phase liquid chromatography with aqueous methanol eluents using the solubility parameter concept model and its derivatives

By recasting the solubility parameter concept model of solute chromatographic behaviour in reversed-phase systems, it is shown that use of the Hildebrand solubility parameter term leads to an inherent overestimation of the retention parameter, k′, by a factor of approximately 4.5. This is similar also to that found using the solubility parameter term for determining the aqueous solubility of liquid solutes. Further, for reversed-phase ODS systems using aqueous methanol eluents, a semi-empirical relationship, based on derivatives of the solubility parameter concept model, has been derived to calculate capacity factors at one eluent composition from those obtained at another. Additionally, it is shown how liquid—liquid distribution coefficients may be used with this semi-empirical relationship to calculate capacity factors directly.

Near-equilibrium LPE growth of In 1− xGa xAs yP 1− y lattice matched to InP

A near-equilibrium solution method is described for LPE growth of In 1− x Ga x As y P 1− y on <100> InP over the wavelength range 1.2⪕λ⪕1.66 μm. Liquid compositions, band gap and distribution coefficients data are presented and compared with data taken by the two-phase method. By using our method melt composition is maintained during growth with a high degree of accuracy. Excellent reproducibility and compositional uniformity have also been achieved.

The role of P2O5 in silicate melts

Phase equilibria data in the systems SiO2-P2O5, P2O5-MxOy, and P2O5-MxOy-SiO2 are employed in conjunction with Chromatographic and spectral data to investigate the role of P2O5 in silicate melts. Such data indicate that the behavior of P2O5 is complex. P2O5 depolymerizes pure SiO2 melts by entering the network as a four-fold coordinated cation, but polymerizes melts in which an additional metal cation other than silicon is present. The effect of this polymerization is apparent in the widening of the granite-ferrobasalt two-liquid solvus. In this complex system P2O5 acts to increase phase separation by further enrichment of the high charge density cations Ti, Fe, Mg, Mn, Ca, in the ferrobasaltic liquid. P2O5 also produces an increase in the ferrobasalt-granite REE liquid distribution coefficients. These distribution coefficients are close to 4 in P2O5-free melts, but close to 15 in P2O5-bearing melts.The dual behavior of P2O5 is explained in a model which requires complexing of phosphate anions (analogous to silicate anions) and metal cations in the melt. This interaction destroys Si-O-M-O-Si bonds polymerizing the melt. The higher concentration of Si-O-M-O-Si bond complexes in immiscible ferrobasaltic liquids relative to their conjugate immiscible granite liquids explains the partitioning of P2O5 into the ferrobasaltic liquid.

Implications of liquid-liquid distribution coefficients to mineral-liquid partitioning

The effect of silicate liquid structure upon mineral-liquid partitioning has been investigated by determining element partitioning data for coexisting immiscible granitic and ferrobasaltic magmas. The resulting elemental distribution patterns may be interpreted in terms of the relative states of polymerization of the coexisting magmas. Highly charged cations (REE, Ti, Fe, Mn, etc.) are enriched in the ferrobasaltic melt. The ferrobasaltic melt is relatively depolymerized due to its low Si O ratio. This allows highly charged cations to obtain stable coordination polyhedra of oxygen within the ferrobasaltic melt. The granitic melt is a highly polymerized network structure in which Al can occupy tetrahedral sites in copolymerization with Si. The substitution of Al +3 for Si +4 produces a local charge imbalance in the granitic melt which is satisfied by a coupled substitution of alkalis, thus explaining the enrichment of low charge density cations, the alkalis, in the granitic melt. P 2O 5 increases the width of the solvus and, therefore, the values of the distribution coefficients of the trace elements. This effect is attributed to complexing of metal cations with PO 4 −3 groups in the ferrobasaltic melt. The values of ferrobasalt-granite liquid distribution coefficients are reflected in distribution coefficients for a mineral and melts of different compositions. The mineral-liquid distribution coefficient for a highly charged cation is greater for a mineral coexisting with a highly polymerized melt (granite) than it is for that same mineral and a depolymerized melt (ferrobasalt). The opposite is true for low charge density cations. Mineralliquid and liquid-liquid distribution coefficients determined for the REE's indicate that fractionated REE patterns are due to mineral selectivity and not the state of polymerization of the melt.

THE EFFECT OF SOLUTE ON SLIP AND MECHANICAL TWINNING IN IRON ALLOYS

The effects of solute type and concentration upon the nature of, and stresses for, plastic flow in polycrystalline iron solid solutions have been examined. An extensive study was made using Al, Be, Ge, P, Si, and Sn; limited examples with Co, Sb, and Ti are also included. Three experimental observations stand out: (i) At room temperature and lower solute concentration the flow stress for slip increases monotonically with the parameter c|ln km|. Here c is the solute concentration, and the solid–liquid distribution coefficient, km, differentiates the solute type, (ii) At room temperature, there is a transition in the deformation mode from slip to twinning at a concentration that decreases with increasing |ln km|. The actual stresses for mechanical twinning can be compared with those at 77 °K; they are higher and provide a second measure for the deformation-mode transition, (iii) At 77 °K the initial deformation mode is predominantly mechanical twinning, and, below concentrations producing atomic ordering, the initial flow stresses are independent of solute concentration and type.When these observations are accompanied by tests for the propagation-controlled phenomenon of continual mechanical twinning, we deduce the following: (i) and (ii) show that solute promotes mechanical twinning as a consequence of its effect on dislocation behavior, most likely by requiring fast-moving individual dislocations, while (iii) shows that a threshold stress exists for the nucleation of mechanical twins that cannot easily be explained by existing twin-nucleation mechanisms.