Extraction of antimony with tertiary amines

The extractability of antimony(III) and (V) with tridodecylamine from various aqueous solutions is reported. Extraction from nitric and hydrofluoric acid solutions is low, but extraction from sulphuric, hydrochloric and hydrobromic solutions is high. Antimony-(III) can be separated from antimony(V) in 7M nitric acid or 0.64M hydrobromic acid. The extraction of antimony from hydrochloric acid solutions in methanol, ethanol, and acetone-water mixtures is greater than from pure aqueous solutions of the same acidity. The elements from which antimony can be separated with tertiary amines are given.     

Crystalline modifications of tetra-(p-tolyl)antimony benzene sulfonate

Two structural isomers (I and II) have been obtained via the crystallization of tetra-(p-tolyl)antimony benzene sulfonate from toluene or water. The antimony atom in compound I has a distorted trigonal bipyramidal coordination to the carbon and oxygen atoms in axial positions (Sb-C, 2.097(11) (eq.), 2.103(10) (eq.), 2.111(10) (eq.), 2.139(10) (ax.) Å; Sb-O, 2.400(7) Å; OSbC, 176.9(3)°, C_eqSbC_eq, 115.3(4)°, 118.7(4)°, 119.1(4)°). A crystal of compound II is built of tetrahedral tetra-(p-tolyl)stibonium cations (Sb-C, 2.097(2), 2.097(2), 2.105(2), 2.106(3) Å; CSbC, 104.68(9)°-117.25(9)°) and benzene sulfonate anions (S-O, 1.439(2), 1.451(2), 1.454(2) Å; OSO, 112.82(15)°-113.70(16)°; OSC, 104.74(13)°-105.78(12)°).     

Microcolumn sorption of antimony(III) chelate for antimony speciation studies

Selective sorption of the Sb(III) chelate with ammonium pyrrolidine dithiocarbamate (APDC) on a microcolumn packed with C₁₆-bonded silica gel phase was used for the determination of Sb(III) and of total inorganic antimony after reducing Sb(V) to Sb(III) by l-cysteine. A flow injection system composed of a microcolumn connected to the tip of the autosampler was used for preconcentration. The sorbed antimony was directly eluted with ethanol into the graphite furnace and determined by AAS. The detection limit for antimony was significantly lowered to 0.007 μg l⁻¹ in comparison to 1.7 μg l⁻¹ for direct injection GFAAS. This procedure was applied for speciation determinations of inorganic antimony in tap water, snow and urine samples. For the investigation of long-term stability of antimony species a flow injection hydride generation atomic absorption spectrometry with quartz tube atomization (FI HG QT AAS) and GFAAS were used for selective determination of Sb(III) in the presence of Sb(V) and total content of antimony, respectively. Investigations on the stability of antimony in several natural samples spiked with Sb(III) and Sb(V) indicated instability of Sb(III) in tap water and satisfactory stability of inorganic Sb species in the presence of urine matrix.     

Crystal structure and luminescence of antimony(III) bromide with aniline

The atomic structure of antimony(III) bromide crystals with anilinium was determined by X-ray diffraction analysis of (C₆H₅NH₃)₂SbBr₅ (a = 19.704(3) Å, b = 7.914(1) Å, c = 25.556(4) Å; space group Pbca, Z = 8, ρ_calc = 2.365 g/cm³). The crystal structure consists of infinite chains of [SbBr₅]^2? complex anions formed by sharing six vertices and the anilinium (C₆H₅NH₃)⁺ cations, through which the chains are linked in layers by N-H...Br hydrogen bonds. The geometrical aspects that determine the luminescent spectral properties of the complex are discussed.     

Extraction with benzene and its derivatives

The extractability of selenium halides with benzene and some of its derivatives has been investigated using a radioactive tracer technique in order to establish the optimum conditions for its extraction. It has been found that Se(IV) is poorly extracted from HCl, HBr or H₂SO₄ solutions but high distribution ratios are observed with binary mixtures of 9M H₂SO₄ and acid halides. The extraction of some other elements is also studied under the conditions selected for Se(IV) extraction and it has been found that only antimony follows Se(IV) in the organic phase. In view of the data obtained, analytical advantages are mentioned and separation procedures are recommended. The extraction mechanism is also discussed and the role of sulfuric acid in the extraction system is explained.     

Cryoscopic studies of amides in benzene

Molal freezing point depression(ΔT_£) of N-methylformamide(NMF), N-methylacetamide(NMA), N-methylpropionamide, N:N-dimethylformamide(DMF), N:N-dimethylacetamide (DMA) and N:N-dimethylpropionamide(DMP) have been determined in benzene by cryoscopic measurements. Molecular weight, degree of association and equilibrium constant have been evaluated from these results. The observed deviations from linear behaviour in ΔT_£^° versus concentration plots appear to indicate the existence of

equilibrium at almost all concentrations for NMF, NMA and NMP compared with the normal linear feature for DMF, DMA and DMP, a novelty which can be explained in terms of hydrogen bonding and which supports our previous conclusions [1] drawn from dielectric measurements.     

Chemical vapor generation for sample introduction into inductively coupled plasma atomic emission spectroscopy: vaporization of antimony(III) with bromide

A new method for antimony determination in soils is proposed. It is based on the chemical vapor generation of Sb(III) with bromide, after a reaction in sulfuric acid media and transport of the gaseous phase into an inductively coupled plasma for atomic emission spectrometry. The experimental variables influencing the method were delimited by experimental design and the most important were finally optimized by the modified Simplex method. In optimized conditions the method involves the reaction of 579 microl concentrated sulfuric acid with 120 microl 5% w/v KBr and 250 microl antimony solution. Measurement of antimony emission intensity at 217.581 nm provides a method with an absolute detection limit of 3.5 ng and a precision (RSD) of 5.8% for the injection of five replicates of 175 ng Sb(III) (250 microl of 0.7 microg ml(-1) solution). The interference of common anions and cations on the antimony signal was evaluated. A 21% Sb(III) volatilization efficiency was calculated from the mean of six experiments at optimum conditions. The accuracy of the methodology was checked by the analysis of one standard reference soil after acid decomposition heating in a microwave oven.     

Physicochemical studies of the cetyltrimethylammonium bromide micellar system using a bromide selective electrode

The use of the bromide selective electrode in physicochemical studies of the cationic micellar system of cetyltrimethylammonium bromide (CTAB) is described. Potentiometric methods and appropriate equations have been developed and used to determine the critical micellar concentration, the ionization degree, and the apparent ion-exchange constants of various anions (fluoride, chloride, hydroxide, acetate, nitrate, sulfate and borate). The interaction of the cationic micelles of CTAB with various species [the lipophilic reagent 1-fluoro-2,4-dinitrobenzene, the anionic succinate and the cationic tris-(hydroxymethyl)-aminomethane] was monitored through the measurement of the changes in the concentration of the free bromide counterions.     

Spontaneous alloying of gold clusters into nanometer-sized antimony clusters

Alloying behavior of gold into nm-sized amorphous antimony (a-Sb) clusters has been studied by transmission electron microscopy (TEM), employing gold clusters in contact with a-Sb clusters. In order to produce gold clusters on individual a-Sb clusters, a-Sb clusters on an amorphous carbon film were cooled down to 96 K, and gold was then condenced on the film. When gold clusters in contact with a-Sb clusters are gradually heated from 96 to 290 K, dissolution of gold into a-Sb clusters sets in around 200K and clusters of a-(Sb-Au) alloys are produced. With increasing annealing temperture, more gold is absorbed into individual a-Sb clusters, and when the gold concentration in a-(Sb-Au) clusters reaches to the stoichiometric composition of AuSb₂, these amorphous clusters crystallize into AuSb2 clusters. The crystallization temperature decreases with decreasing size of initial a-Sb clusters.     

Thermal decomposition of complexes of antimony(III) bromide with hydrobromides of some aromatic amines

Thermal studies have been carried out on crystalline complexes formed between antimony(III) bromide and hydrobromides of some aromatic amines in concentrated hydrobromic acid solutions. Thermal analysis curves of the compounds under study are presented. Kinetic parameters of the thermal decomposition reactions were calculated from the TG curves using the Horowitz—Metzger method. A comparison of the thermal stabilities of the complexes was made.     

Specular reflectance studies of bromide adsorption on gold

Specular reflectance changes have been used to examine the specific adsorption of bromide on gold in the presence of a large excess of supporting electrolyte (NaF) which is not specifically adsorbed. A linear relation has been demonstrated between the reflectance changes and the surface excess of bromide through the examination of the time dependence of the reflectance under conditions where the rate of adsorption of the bromide is diffusion controlled and hence known. The adsorption isotherms have been found to follow Temkin behavior. The electrosorption valency has been evaluated from the charge and surface excess at constant potential and found to be ?0.49 to ?0.59, depending on the potential. Various mechanisms for the subtantial changes in reflectance attending the specific adsorption of anions are discussed. The observed effects cannot be explained on the basis of changes in the charge on the electrode and corresponding changes in the contribution of the conduction band to the surface optical properties. The principal mechanism is proposed to be modifications in the surface electronic states of the metal electrode through direct orbital interactions between the adsorbed anions and the metal.     

Study of complex formation between aluminum bromide and benzene by 27Al NMR spectroscopy

The reaction of aluminum bromide with benzene in n-hexane was studied by ²⁷Al NMR spectroscopy in the temperature range from –80 to +20 °C. The formation of C₆H₆·Al₂Br₆ (1 : 2) complexes is accompanied by broadening of the resonance line with 178. No peak splitting following a decrease in the temperature was observed but the temperature dependence of the line width passed through a maximum near –60 °C. A procedure for determination of the constant K for the formation of 1 : 2 complexes at –20, 0, and +20 °C based on the line broadening with an increase in the C₆H₆ : Al₂Br₆ molar ratio was proposed. The thermodynamic parameters of complex formation, G, H, and S, were calculated.     

Extraction of zinc thiocyanate complex by tributyl phosphate in benzene

The species extracted is shown to be Zn(SCN)X.2TBP, where X is a common anion. Good separation factors are obtained for extraction of zinc from solutions containing silver(I), manganese(II), cobalt(II), cadmium(II), mercury(II) and thallium(III).     

Speciation analysis of antimony in marine biota by HPLC-(UV)-HG-AFS: Extraction procedures and stability of antimony species

Speciation analysis of antimony in marine biota is not well documented, and no specific extraction procedure of antimony species from algae and mollusk samples can be found in the literature. This work presents a suitable methodology for the speciation of antimony in marine biota (algae and mollusk samples). The extraction efficiency of total antimony and the stability of Sb(III), Sb(V) and trimethylantimony(V) in different extraction media (water at 25 and 90 °C, methanol, EDTA and citric acid) were evaluated by analyzing the algae Macrosystis integrifolia (0.55 ± 0.04 μg Sb g⁻¹) and the mollusk Mytilus edulis (0.23 ± 0.01 μg Sb g⁻¹). The speciation analysis was performed by anion exchange liquid chromatography (post-column photo-oxidation) and hydride generation atomic fluorescence spectrometry as detection system (HPLC-(UV)-HG-AFS). Results demonstrated that, based on the extraction yield and the stability, EDTA proved to be the best extracting solution for the speciation analysis of antimony in these matrices. The selected procedure was applied to antimony speciation in different algae samples collected from the Chilean coast. Only the inorganic Sb(V) and Sb(III) species were detected in the extracts. In all analyzed algae the sum of total antimony extracted (determined in the extracts after digestion) and the antimony present in the residue was in good agreement with the total antimony concentration determined by HG-AFS. However, in some extracts the sum of antimony species detected was lower than the total extracted, revealing the presence of unknown antimony species, possibly retained on the column or not detected by HPLC-(UV)-HG-AFS. Further work must be carried out to elucidate the identity of these unknown species of antimony.     

Kinetic studies of underpotential deposition of antimony on Se-modified Au electrode

Atomic layers of antimony can be electrodeposited onto the Se monolayer covered Au electrode in the underpotential region. In this paper, the formation and dissolution kinetics of antimony monolayer on the Se monolayer covered Au electrode are investigated using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Scanning-rate-dependent CV experiments reveal that the peak current of underpotential deposition (UPD) wave of antimony is not a linear function of the scanning rate, υ, but scales as υ ^2/3. Similar behavior is observed when the Antimony monolayer is stripped from the modified substrate. These results indicate the character of monolayer formation and dissolution by a two-dimensional nucleation and growth mechanism. Additionally, current density−time transient obtained through CA experiments also reveal that both the deposition and stripping of the antimony monolayer involve an instantaneous nucleation and two-dimensional growth process.     

Introduction of substituents into the benzene nucleus of indole

A method for the synthesis of indolinopyrazines has been proposed. The possibility has been shown of dehydrogenating the indolinopyrazines to the corresponding indole derivatives.For part IX, see [1].     

Determination of antimony in poly(ethylene terephthalate) by volatile bromide generation flame atomic absorption spectrometry

A chemical volatilization method has been developed for the determination of antimony in poly(ethylene terephthalate) (PET), after a simple acid digestion using discontinuous volatile generation and efficient introduction to a flame atomic absorption spectrometer (FAAS). The method has been evaluated and optimized by different approaches which included experimental design, numerical evaluation, visual interpretation of 3-D surface response, and artificial neural network. Its performance showed a detection limit (3s) of 300 ng as the absolute detection limit for a sample injection of 215 μL. The linear response, at 217.6 nm, ranged from 1.0 to 17.2 μg of Sb(V), with a reproducibility of 4.5 (% r.s.d.). The Sb content in PET analyzed by this method was found in the range 98–190 mg·kg⁻¹, which was in good agreement with an ICP-AES standard method, and demonstrated a low level of interferences.     

Introduction of substituents into the benzene ring of indole

A number of dinitro-2-methylindolines (5,6-, 6,7-, and 5,7-) were synthesized by the nitration of nitro-2-methylindoline isomers. The positions of the nitro groups in each case were proved by means of NMR and electronic spectra.See [6] for communication XII.Deceased.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 953–955, July, 1971.     

Introduction of substituents into the benzene nucleus of indole

A number of derivatives of 6,7-dihydroimidazolo[4,5-f]indole, imidazolo[4,5-f]indole, 6,7-dihydroimidazolo[4,5-f]indol-2(3H)-one, and 6,7-dihydrotriazolo[4,5-f]indole has been synthesized from 1-acetyl-5,6-diaminoindoline and 5,6-dinitroindoline.For Communication XI, see [7].Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 6, pp. 770–774, June, 1970.