Ion flotation of cadmium using ethylhexadecyldimethylammonium bromide

Cadmium ions react with the collector, ethylhexadecyldimethylammonium bromide (EHDABr), to form a surface-active sublate which can be removed from aqueous bromide

a. Effect of Foreign Metal Ions on the Flotation of Cadmium^a

Foreign ion	Foreign ion concentration (M) (×10?5)	Foreign ion removed (%)	Cadmium removed (%)
None			99.21
Zn2+	6.11	0.06	98.41
Cu2+	6.29	3.64	97.80
Pb2+	3.86	4.80	91.78
Cr6+	7.69	30.75	99.07 solutions by ion flotation. A typical ion flotation procedure involves passing air through a 250-ml solution containing 5 ppm Cd2+, 0.05 M Br?1, and 1.7 × l0?3M EHDABr at a flow rate of 40 ml/min for 1 hr. The procedure was simple and efficient. Chromium, copper, and zinc ions do not interfere under the experimental conditions.

a

Cd²⁺, 4.46 × 10^?5M; EHDABr, 4.25 × 10^?4; Br^?, 5 × 10^?2M; flow rate, 40 ml/min; time, 60 min.

     

Kinetics of the Hg(II)/Hg electrode reaction in DMSO solutions of chloride ions

The electrode reaction Hg(II)/Hg in complex chloride solutions with dimethyl sulfoxide as solvent has been investigated at the equilibrium potential by the faradaic impedance method and a cyclic current-step method. The ionic strength was 1 M with ammonium perchlorate as supporting electrolyte, and the temperature was 25°C. Double-layer data have been determined by electrocapillary measurements. From the results of the kinetic measurements at ligand numbers ≤1.1 or ≥2.3 it is concluded that the overall charge transfer proceeds step-wise. The solvated Hg²⁺ and Hg₂²⁺ as well as the complexes HgCl_j^2?j and the dinuclear Hg₂Cl³⁺ contribute to the exchange current density. The rate constant of the step HgCl_j^2?j/ Hg(I) is found to increase with the number of Cl^? coordinated. This increase can be correlated to a decrease in solvation and a lengthening of the Hg?Cl distance. For 1.1 << 2.3, impedance measurements indicate a rate-controlling adsorption step. It is suggested that the uncharged HgCl₂ then forms an adsorbed network on the mercury surface.     

Microdetermination of acetone in aqueous solution

Diazotized anthranilic acid has been found to be a possible reagent for the spectrophotometric microdetermination of acetone in aqueous solution. The determination range is 10–130 μg/ml. The coefficient of variation does not usually exceed 12% for 60–130 μg of acetone but increases to 2.8% at the 10-μg level. The average relative error for five determinations ranges from ?1.5 to 2%. The molar absorptivity is 9.28 × 10³ liter · mol^?1 · cm^?1 in the presence of starch as a surfactant. Possible reaction path mechanism has been suggested for the colored body formation.     

Liberation of excess energy and retransformation of mechanically activated cadmium sulphide

On heating vibro-milled CdS containing the strained high-pressure rock salt phase, the excess energy was gradually liberated accompanied by the retransformation into more stable phases and the restoration of their crystallinity. Profiles of DSC curves, inter-relationships between thermal and crystallographical properties, the stability of each phase and the mechanism of the mechanochemical activation are discussed. A direct retransformation of the strained high-pressure phase was found to accompany the liberation of the excess energy.     

Electrochemical reduction of some rhodanine derivatives at the DME

The electroreduction of two series of rhodanine derivatives has been investigated at the DME. The first wave was assigned to the saturation of the azomethine linkage and the reduction of the ethylenic double bond in series I and II, respectively. On the other hand, the second wave in both series was assigned to the reduction of the C-S group and partly to the catalytic hydrogen evolution catalyzed by these compounds.     

Electrochemical oxidation of multisulfur heterocycles reactions of dithiane cations in acetonitrile

The electrochemical oxidation in acetonitrile of two orthothiooxalates containing 1,3-dithiane rings proceeds via rearrangement reactions of cationic intermediates to form the dication of an endocyclic tetrathioethylene. The dication undergoes a subsequent rearrangement, a possible example of a dyotropic reaction, to complete the electrode reaction. The electrochemical behavior was established by independent synthesis of the product tetrathioethylene, 2,6,8,12-tetrathiabicyclo(5.5.0)dodec-1(7)-ene, its electrochemical behavior, and the electron spin resonance spectra of the radical cations obtained by electrolytic generation from solutions of the orthothiooaxalate and suspected tetrathioethylene oxidation products. When the electrochemical oxidative pathway is compared to the thermal and electron-impact induced fragmentation reactions, distinct differences are noted.     

Electrochemical bromination of benzene,toluene and xylene in acetonitrile

A method for the preparation of bromo derivative compounds of aromatics is proposed and the electrodic process involved in the bromination on the third wave of the system Br^?/aromatic substrate in acetonitrile is discussed.     

Poloxamer association in aqueous solution

Aqueous solutions of the surface active poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) block copolymers (poloxamers) were studied using photon correlation spectroscopy (quasi-elastic light scattering) and viscosity measurements. Poloxamers 184 and 237 showed detectable aggregates at 25° only at concentrations above about 6% with size increasing with concentration and with significant polydispersity, probably indicating a multiple association process. At 35°, however, essentially invariant values for the hydrodynamic radius were found over a wide concentration range and the systems were essentially monodisperse: these systems are more likely to be represented by a closed association model. The more hydrophilic poloxamer 188, however, retained its concentration dependence of aggregate size up to 55°. The variation with temperature of both the hydrodynamic radius of aggregates and the intrinsic viscosity of several poloxamers was rationalized by relating the temperature-dependency curves to the cloud point of the poloxamer. In some cases only certain sections of the curve are observable when the cloud point is high, e.g., >100°, or low, e.g., <40°.     

Crystal and molecular structures of diphenylethylarsine sulfide,C14H15AsS,and p-tolyldiethylarsine sulfide,C11H17AsS

In order to elucidate the influence of aryl or alkyl substituents on the nature of the ? bond, which controls the complexing properties of the substances (Alk)n(Ar)_3-nAsS (n = 0–3), the X-ray investigation of (p-MeC₆H₄)Et₃AsS (TDEAS) and Ph₂EtAsS (DPEAS) has been carried out. It was shown that the bond length AsS in these compounds has intermediate values (2.0896 and 2.0812 Å) in respect to those previously found by us in Et₃AsS and Ph₃AsS (2.115 and 2.077 Å). This confirms the conclusion that the increase of the number of aryl substituents in tertiary arsine sulfides leads to a decrease of electron density on the As atom along with simultaneous strengthening of the π-interaction between As and S.     

Thermoanalytical behavior of cadmium(II) oxide—alkali persulfate binary systems

The non-isothermal behavior of two binary CdO—persulfate systems has been investigated. The molar ratios and T_i—T_f are established. The temperatures for the α- to β-Na₂SO₄ phase transition, as well as for α- to β- to γ-CdSO₄ of the CdONa₂S₂O₈ system have been fixed. No evidence for the occurrence of the β- to γ-CdSO₄ polymorphic trans-formation has been obtained from the reaction of the CdOK₂S₂O₈ system. This is because of the formation of a CdSO₄/K₂SO₄ eutectic mixture which melts at 653°C, i.e., before the β- to γ-phase change transition, which usually occurs later. No basic cadmium sulfate has been identified. The excess cadmium oxide acts as a p-type semiconductor which accelerates the thermal decomposition of pyrosulfates.     

Spectrophotometric and analogue derivative spectrophotometric determination of ultramicro amounts of cadmium with cationic porphyrins

alpha,beta,gamma,delta-Tetrakis(1-methylpyridinium-3-yl)porphine [T(3-MPy)P] and alpha,beta,gamma,delta-tetrakis(1-methylpyridinium-4-yl)porphine [T(4-MPy)P] have been found to react rapidly with cadmium to give coloured complexes in weakly alkaline media at room temperature. Simple and practical methods for the determination of cadmium at ng/ml levels by conventional and analogue derivative spectrophotometry have been proposed. The analogue method gives higher sensitivity. T(3-MPy)P gives higher sensitivity than T(4-MPy)P. The interference of various foreign cations and anions has also been examined and in many cases eliminated or reduced. Adsorption of the porphyrins and their cadmium complexes onto the glassware, which is usually observed under the conditions of reaction and causes significant errors in the determination, can be suppressed almost completely by addition of fairly large amounts of a salt such as sodium chloride.     

Electrochemical behavior of decyl mercuric halides at mercury cathodes in dimethylformamide

Polarograms for decyl mercuric halides in dimethylformamide containing tetraalkylammonium perchlorates exhibit two waves. When large-scale electrolyses of decyl mercuric halides are performed at potentials corresponding to the first polarographic wave, the couldometric n value is unity and didecylmercury is obtained in quantitative yield; electrolyses carried out at potentials on the plateau of the second polarographic wave afford only decane and the n value is essentially 2. Double-potential-step chronocoulometry and staircase voltammetry indicate that, at potentials corresponding to the first polarographic wave, the decyl mercuric halide (which is itself adsorbed onto mercury to the extent of less than a monolayer) undergoes reversible one-electron reduction to adsorbed decyl mercury radicals and to adsorbed decyl mercury radical “polymer”; the adsorbed radicals have a lifetime of approximately 10^?3s and disproportionate into didecylmercury and elemental mercury. In the presence of electrolytically released halide ion, the adsorbed radicals are reoxidized to the decyl mercuric halide; alternately, the adsorbed species are reoxidized to decyl mercury cations at a potential approximately 600 mV more positive than that required for reoxidation to the decyl mercuric halide. At potentials corresponding to the second polarographic wave, reduction of decyl mercuric halides is an irreversible process producing decyl carbanions which are protonated by traces of water in the solvent to give decane.     

Cadmium-113 and carbon-13 nuclear magnetic resonance spectrometry of cadmium peptide complexes

The cadmium complexes of glycylglycine, glycylglycylglycine, glycyl-gamma-aminobutyric acid and beta-alanylglycine (beta-Ala-Gly) have been investigated by (113) Cd and (13)C nuclear magnetic resonance spectrometry. The minima observed in plots of the (113)Cd chemical shift vs. pH are consistent with cadmium binding first at the carboxylic site and then at the amino-group site. The chemical shift vs. pH profile for the beta-Ala-Gly system is different from that for the other peptides, and is interpreted as suggesting formation of a five-membered chelate between Cd(II) and glycyl residues at the N-terminal groups and not at the C-terminal groups. The data further indicate that the NH groups of the peptide linkages are probably not involved in complexation with cadmium. Finally, a reported pH-dependent (113)Cd resonance for parvalbumin has been reassigned.     

Partial phase diagrams for the water—cadmium nitrate, water—silver nitrate and water—cadmium nitrate—silver nitrate systems

Sub-ambient differential scanning calorimetry has been used to determine partial binary phase diagrams for the water—silver nitrate and water—cadmium nitrate systems. Both systems are shown to be eutectic with eutectic temperatures of 263 ± 0.5 K and 256.5 ± 0.5 K for the water—silver nitrate and water—cadmium nitrate systems, respectively. The eutectic compositions are at approximately 40.5 wt.% nitrate for each system. The freezing of ternary solutions containing a fixed silver nitrate/cadmium nitrate ratio but increasing concentrations of total nitrates are explained in terms of a partial ternary system containing two binary eutectic systems and a ternary eutectic reaction. The ternary eutectic temperature is shown to be 254 ± 0.5 K.     

Electrical transport properties of a nonstoichiometric rare earth sulfide,EuGd2S4

The electrical transport properties of nonstoichiometric EuGd₂S₄ prepared by heating under a high vacuum have been investigated. The samples heated were classified into two groups on the basis of their electrical transport behavior. One group comprised semiconducting materials heated at 1500 and 1600°C, for which the transport mechanism was found to be via electron hopping with activation energies ranging from 0.013 to 0.027 eV. Another group comprised metallic materials heated at 1700 and 1800°C. Their electrical transport was carried out through ordinary band conduction over the measured temperature range except at temperatures lower than 120°K, where hopping with a very small activation energy (～0.0035 eV) occurred predominantly.