Ion flotation of rhodium(III) and palladium(II) with anionic surfactants

The ion flotation of rhodium(III) and palladium(II) with some anionic surfactants has been investigated. Two flotation procedures are proposed for the separation of some platinum metals, based on differences in the kinetic properties of the chloro-complexes of rhodium(III), palladium(II) and platinum(IV). The first involves the selective flotation of Rh(H(2)O)(3+)(6) from PdCl(2-)(4) and PtCl(2-)(6) in dilute hydrochloric acid with sodium dodecylbenzenesulfonate (SDBS). After precipitation of the hydroxide and redissolution in dilute acid, the Rh(III) is converted into Rh(H(2)O)(3+)(6), Pd(II) and Pt(IV) remaining as PdCl(2-)(4) and PtCl(2-)(6) respectively, and separation is achieved by floating the Rh(H(2)O)(3+)(6) with SDBS. The second is for separation of Pd(II). Prior to flotation, the solution of PdCl(2-)(4) and PtCl(2-)(6) is heated with ammonium acetate to convert PdCl(2-)(4) into Pd(NH(3))(2+)(4). The chloro-complex of Pt(IV) is unaffected. The complex cation, Pd(NH(3))(2+)(4), is then selectively floated with SDBS. The procedures are fast, simple and do not require expensive reagents and apparatus.     

Lanczos cluster expansion for non-extensive systems

A cluster expansion of the Lanczos recursion for non-extensive systems is developed based on the plaquette expansion for extensive systems, in which an auxiliary scaling parameter, Ω, plays the role of volume and introduces extensivity into the problem. Connected Hamiltonian moments of the non-extensive system are computed and introduced into the plaquette expansion in the usual way with Ω. The extensive energy is calculated for increasing orders of the expansion in 1/Ω and the ground state and mass gap of the finite few body problem recovered in the limit Ω → ∞. This new non-perturbative method is applied to the case of N bosons interacting harmonically in one dimension and the ground state energy and mass gap in the vacuum sector are calculated exactly.     

Catalytic cathodic stripping voltammetry of oxidized glutathione at a hanging mercury drop electrode in the presence of nickel ion

Oxidized glutathione (GSSG) can be determined after previous accumulation on the HMDE at E > -0.2 V (vs. the Ag AgCl reference electrode). GSH is formed during the accumulation, possibly by a mercury-ion-assisted hydrolytic disproportionation of GSSG. In the subsequent cathodic scan GSH is released and catalyses the reduction of nickel ion, giving a peak located at -0.6 V. This enables the determination of GSSG by differential-pulse cathodic stripping voltammetry at pH 7.0 in the phosphate acetate or MOPS buffer containing 0.5-1.0 mM Ni(II). The detection limit is 10 nM. The calibration graph is linear even in the presence of small amounts of human serum albumin, HSA. However, HSA increases the detection limit (20 nM for 3 x 10(-4)% HSA). Acetyl-cysteine in small excess or Cu(II) present as reagent impurity do not interfere. Glutathione, cysteine and similar compounds, which accumulate as mercury salts and form stable nickel complexes, will interfere. The method is put forward as a novel alternative stripping voltammetric method to those involving accumulation and determination as mercury or copper salts and complexes, in the knowledge that it may have advantages in particular analytical situations. In particular the method discriminates against compounds which accumulate as mercury salts but which do not form stable nickel complexes.     

A study of the molar absorptivity of ascorbic acid at different wavelengths and pH values.

A spectral study of ascorbic acid was made in buffer solutions of different pH. The molar absorptivities of the unionized (?_HA) and ionized (?_A-) forms of ascorbic acid were determined at six wavelengths. An isosbestic point occurs at 250.7 nm; the molar absorptivity at this wavelength is 8250 ± 150 l mol^-1 cm^-1. The spectral information presented is of importance for the spectrophotometric assay of samples containing vitamin C.     

Biological generation of tritiated vitamin D3 metabolites and their purification by high-performance liquid chromatography

Summary A simple, reproducible method for the biological synthesis of tritiated 24,25-dihydroxycholecalciferol, 25,26-dihydroxycholecalciferol and 1,25-dihydroxycholecalciferol is described. Kidney homogenates from both vitamin D deficient and replete chicks were usedin vitro to generate these dihydroxylated metabolites using 25 (23,24-³H) hydroxycholecalciferol as the substrate. Tritiated products were purified by Sephadex LH 20 chromatography followed by high-performance liquid chromatography; the identity of each metabolite was established by chromatography with authentic crystalline preparations.Presented at the Symposium organised by the Chromatography Discussion Group, held at Hatfield Lodge on 29 November 1979.     

Methods of separation of subcellular particles

Summary Some recent developments in the field of tissue fractionation are briefly reviewed. Separation techniques have been improved considerably, thanks mainly to the construction of various automatic rotors for density gradient centrifugation. Progress has also been made in the analysis of the fractions, through automation of biochemical techniques, and especially through the use of quantitative morphological methods.

---

Trennverfahren subcellularer Teilchen

Zusammenfassung Ein Überblick über neuere Entwicklungen auf dem Gebiet der Gewebefraktionierung wird angegeben. Die Trennverfahren konnten wesentlich verbessert werden, hauptsächlich durch die Konstruktion verschiedener automatischer Rotoren zum Zentrifugieren mit Dichtegradient. Auch die Analyse der Fraktionen wurde durch Automation biochemischer Verfahren und besonders durch den Einsatz quantitativer morphologischer Methoden weitgehend verbessert.

     

Coleon D,ein Diterpen aus Coleus aquaticus Guercke mit trans-A/B-6,7-Dioxostruktur

Coleon D, C₂₀H₂₆O₆ a new orange red diterpenoid hydroquinone has been isolated from the yellow glands on the leaves and inflorescences of Coleus aquaticus Guercke (Labiatae). Its structure has been determined as 11,12,14,16-tetrahydroxy-5α-abieta-8,11,13-trien-6,7-dion ( 1 ) Therefore it is a tautomer of Coleon C ( 2 ). Coleon D is the precursor of Coleon C.     

The preparation,isomerization, and characterization of some phosphagerma- and arsagermacarboranes

Treatment of the disodium salts of 7,8- and 7,9-B₉H₉CHE^2? with germanium diiodide in refluxing benzene results in the formation of 1,2,3- and 1,2,7-GeB₉H₉CHE (E = P or As), icosahedral boranes containing three different heteroatoms in the cage. Heating 1,2,7-GeB₉H₉CHP at 512° for 8 hours in an evacuated sealed tube yields a mixture of three new isomers one of which has been isolated and characterized.     

Dielectric Shielding of Ionic Charges in Aqueous Solutions of Different Ionic Strength

The thermodynamic functions of the proton transfer H₂tn²⁺+tn → 2 Htn⁺ (tn = 1,3-diaminopropane) have been determined in aqueous solutions containing different amounts of KCl (0.05 ? μ ? 3.01). The free energy (?ΔG) of the process decreases, whereas the enthalpy (-ΔH) increases with μ. There is reason to believe that the reaction is entirely controlled by the Coulomb forces between the two protonic charges. The electrostatic energy involved can be described in terms of a model incorporating an effective dielectric constant εe, such that δε_e/δμ and δ²ε_e/δμδT are both positive. The polarisation of pure water is produced by orientation of hydrogen-bonded dipole molecules H₂O, whereas the electrolyte solution is polarised in addition by dislocation of the ions K⁺ and Cl^?. Our results demonstrate that the former type of polarisation is much more temperature dependent than the latter.     

Modeling of ultralyophobicity: suspension of liquid drops by a single asperity

With the aim of understanding the underlying physical phenomenon associated with utlralyophobic (or super repellent) surfaces, model studies have been performed on single asperities of different size and shape. A small liquid drop was deposited on top of each model asperity, and liquid was sequentially added. If the advancing contact angle was sufficiently large, it was possible to suspend large drops atop asperities with an apparent contact angle approaching 180 degrees. If more and more liquid was added, eventually the suspended drops collapsed. Roughening the surface of the asperities further bolstered suspension. Using an analysis that accounts for both capillary forces and the influence of gravity, the critical suspension volume was correctly predicted for each liquid/asperity combination.