Solvent extraction separation of tin (IV) with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A)

Solvent extraction of tin(IV) from hydrochloric acid media was carried out with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) in toluene. Tin(IV) was quantitatively extracted with 2.5x10(-2) M PC-88A in toluene from 0.1-0.3 M HCl when equilibrated for 5 min. Tin(IV) from the organic phase was stripped with 4 M HCl and determined spectrophotometrically by both the morin and pyrocatechol violet method. The nature of the extracted species was determined from the log-log plots. Various other diluents such as xylene, hexane and cyclohexane also gave quantitative extraction of tin. The metal loading capacity of the reagent was found to be 0-15 ppm of tin(IV). The extraction of tin(IV) was carried out in the presence of various ions to ascertain the tolerance limit of individual ions. Tin(IV) was successfully separated from commonly associated metal ions such as antimony(III), bismuth(III), lead(II), thallium(I), copper(II), nickel(II), etc. The method was extended for determination of tin in real samples.     

Precipitation of lead as lead sulphate by destructive oxidation of EDTA

Gravimetric determination of lead (5–100 mg) by homogeneous precipitation of lead sulphate from a solution containing lead(II), EDTA and sulphate by destructive oxidation of EDTA with hydrogen peroxide or sodium bromate is described. Aluminium(III), iron(III), zinc(II), manganese(II), copper(II), nickel(II), tin(II) and antimony(III) do not interfere in the method. The method can successfully be applied to the analysis of type metal.     

Some aspects of n-benzoylphenylhydroxylamine and cupferron reactions with tin,antimony and other selected elements

N-Benzoyl-N-phenylhydroxylamine (BPHA) and cupferron are compared in the liquid-liquid extraction of tin and antimony. As in their precipitation reactions tin(II) and tin(IV) behave similarly with BPHA and differently with cupferron. Both reagents behave similarly in extraction of antimony (III), except at high acidity when cupferron or its decomposition products prevent extraction which otherwise occurs into chloroform alone. Separations of Sn, Sb, As and Bi are discussed for extractions from hydrochloric and perchloric acid systems with BPHA. The tin product extracted with BPHA from dilute hydrochloric acid appears to be identical with that precipitated in gravimetric analysis; infrared spectral evidence shows the latter to contain tin(IV). Other precipitation reactions of BPHA in the presence of anions other than chloride and some solubility measurements are also reported.     

Use of isooctyl thioglycolate for the separation of tin and antimony

The extraction characteristics of isooctyl thioglycolate (IOTG), a chelating agent, in various diluents has been studied with respect to the metal ions, tin(IV) and antimony(III), in hydrochloric acid medium. It is concluded that antimony(III) can be separated from tin(IV) with 85% yield and with a decontamination factor of at least 1·10⁵ using IOTG diluted with petroleum ether and 3M HCl medium. Tin(IV) can be separated conveniently from antimony(III) in 2M HCl with 95% yield and with a decontamination factor greater than 7·10⁵ using IOTG diluted with carbon tetrachloride.     

Analytical applications of a liquid anion-exchanger for the separation of uranium(IV) in malonate solution

Uranium was quantitatively extracted with 4% Amberlite LA-1 in xylene at pH 2.5-4.0 from 0.001 M malonic acid. It was stripped from the organic phase with 0.01 M sodium hydroxide and determined spectrophotometrically at 530 nm as its complex with 4-(2-pyridylazo) resorcinol. Of various liquid anion-exchangers tested, Amberlite LA-1 was found to be best. Uranium was separated from alkali and alkaline earth metal ions, thallium(I), iron(II), silver, arsenic(III) and tin(IV) by selective extraction, and from zinc, cadmium, nickel, copper(II), cobalt(II), chromium(III), aluminium, iron(III), lead, bismuth, antimony(III) and yttrium by selective stripping. The separation from scandium, zirconium, thorium and vanadium(V) was done by exploiting differences in the stability of chloro-complexes.     

Determination of antimony in concentrates, ores and non-ferrous materials by atomic-absorption spectrophotometry after iron-lanthanum collection, or by the iodide method after further xanthate extraction

Methods for determining trace and moderate amounts of antimony in copper, nickel, molybdenum, lead and zinc concentrates and in ores are described. Following sample decomposition, antimony is oxidized to antimony(V) with aqua regia, then reduced to antimony(III) with sodium metabisulphite in 6M hydrochloric acid medium and separated from most of the matrix elements by co-precipitation with hydrous ferric and lanthanum oxides. Antimony (>/= 100 mug/g) can subsequently be determined by atomic-absorption spectrophotometry, at 217.6 nm after dissolution of the precipitate in 3M hydrochloric acid. Alternatively, for the determination of antimony at levels of 1 mug/g or more, the precipitate is dissolved in 5M hydrochloric acid containing stannous chloride as a reluctant for iron(III) and thiourea as a complexing agent for copper. Then tin is complexed with hydrofluoric acid, and antimony is separated from iron, tin, lead and other co-precipitated elements, including lanthanum, by chloroform extraction of its xanthate. It is then determined spectrophotometrically, at 331 or 425 nm as the iodide. Interference from co-extracted bismuth is eliminated by washing the extract with hydrochloric acid of the same acid concentration as the medium used for extraction. Interference from co-extracted molybdenum, which causes high results at 331 nm, is avoided by measuring the absorbance at 425 nm. The proposed methods are also applicable to high-purity copper metal and copper- and lead-base alloys. In the spectrophotometric iodide method, the importance of the preliminary oxidation of all of the antimony to antimony(V), to avoid the formation of an unreactive species, is shown.     

Effect of dielectric constant on Rf values of metal ions in some formic acid-alcohol solvent systems

Correlations between dielectric constant and R(f) values for numerous alcohol-formic acid systems have been made. Most metal ions behave similarly, but arsenic(III), antimony(III) and tin(II) show different properties.     

Extraction-spectrophotometric determination of traces of antimony in copper and lead metals and in lead-base alloy with pyrocatechol violet and tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of antimony in copper and lead metals and in lead-base alloy. Optimal conditions have been established for the extraction and determination of antimony. Antimony (III) is extracted from a potassium iodide—sulfuric acid or a hydrobromic—sulfuric acid medium with toluene and converted to an antimony-pyrocatechol violet (PV) complex. The complex is then extracted with tri-n-octylamine (TOA) and the absorbance of the resulting ternary Sb(III)—PV-TOA complex is measured at 555 nm. As little as 0.5 p.p.m. of antimony in copper metal and 0.2 p.p.m. of antimony in lead metal and lead-base alloy can be determined.     

Spectrophotometric determination of tin(IV) by extraction of the ternary tin/iodide/5,7-dichloro-8-quinolinol complex

The characteristics of the ternary complexes formed by fluoride, bromide, iodide and thiocyanate with tin(IV) and 5,7-dichloro-8-quinolinol (HCQ) have been studied. A spectrophotometric method is proposed for the determination of tin(IV) (1–20 μg ml^?1), based on the extraction into chloroform of the tin/iodide/HCQ complex. Aluminium, bismuth and lead do not interfere, but antimony, copper, iron(III) and fluoride do. Copper and iron can be eliminated by preliminary extraction in the absence of iodide.     

Rapid Solvent Extraction of Tin(IV) with High Molecular Weight Amine from Hydrochloric Acid Solution

A novel method has been developed for the solvent extraction of tin(IV) from 8 M hydrochloric acid with 4% N‐n‐octylaniline. Tin(IV) from the organic phase was determined spectrophotometrically with pyrocatechol violet at 550 nm. Extraction was found to be quantitative in the range of 7–10 M hydrochloric acid. When the concentration of N‐n‐octylaniline was varied from 0.05–20% in xylene, it showed that optimum concentration was > 3%. Amongst diluents like benzene and xylene, toluene was found to be an effective diluent. Effect of shaking time, concentration of metal ion, and salting out agents was studied. Tolerance limits of various diverse ions were determined by masking interfering cations. Tin(IV) was separated from associated elements in its binary mixture with Se(IV), Sb(III), Bi(III), Pb(II), Au(III), Cu(II) and Zn(II) and from its ternary mixtures with Sb(III), Bi(III) and Cu(II), Au(III). The proposed method was applied for separation and determination of tin(IV) in tin bearing alloys and foodstuffs.     

Synthesis and spectroscopic characterization of arsenic(III), antimony(III), bismuth(III), tin(II) and lead(II) dithiocarbamate adducts

The complexes of arsenic(III), antimony(III), bismuth(III), tin(II) and lead(II) with monomethylsubstituted piperidinodithiocarbamates of general formula M(Rdtc)₃ and M(Rdtc)₂ have been prepared and characterized by spectroscopic methods. The results of the spectroscopic studies indicate that the dithiocarbamate ligands are always bidentate, in both the 1:3 and the 1:2 complexes. All the complexes are nonconducting in DMF solution. The thermal behaviour of the complexes has been investigated by TG and DTG techniques. The molecular weight determinations indicate that the trisdithiocarbamates of arsenic and antimony are monomeric, while the bismuth trisderivatives tend to dimerize: polymeric structures can be suggested for the tin(II) and lead(II) compounds.     

Determination of arsenic and selenium in steel by an X-ray technique utilizing chemical preconcentration

A chemical X-ray method is proposed for determining trace amounts of arsenic and selenium in steel. The method utilizes a prechemical separation from the iron matrix and concentration of arsenic and selenium on a micr?pore membrane by reduction to the free metal by tin(II). Selenium was found to be a suitable carrier for arsenic (300 mug of selenium for the quantitative precipitation of 10-200 mug of arsenic). Arsenic (300 mug) was found to be a suitable carrier for up to 200 mug of selenium. Up to 200 mug of tellurium and antimony were experimentally found not to be co-precipitated with either arsenic or selenium.     

A volumetric determination of arsenic and antimony in mixed manganese arsenide,antimonide and phosphide compounds

A procedure is described for the titrimetric determination, of arsenic and antimony without separation. Total combined arsenic and antimony were determined by reduction with tin(II) chloride and titration with permanganate; antimony is found by selective reduction with mercury(I) chloride and titration with permanganate. A precision of 0.1–0.2% was obtained for total combined arsenic and antimony, and approximately 1% for antimony alone (small amounts in the presence of large amounts of arsenic). The procedure was developed for and applied to the analysis of synthesized compounds of the type MnAs_1-xP_x and MnAs_1-ySb_y.     

Determination of Sn(II) and Sn(IV) after mixed micelle-mediated cloud point extraction using alpha-polyoxometalate as a complexing agent by flame atomic absorption spectrometry

The cloud point extraction behavior of Sn(II) and Sn(IV) using alpha-polyoxometalate and mixed surfactants solution was investigated. The mixture of a nonionic surfactant (Triton X-100) and a cationic surfactant (CTAB) was utilized as a suitable micellar medium for preconcentration and extraction of tin complexes. Sn(II) in the presence of Sn(IV) was extracted with alpha-polyoxometalate, 0.3% (w/v) Triton X-100 and 3.5x10(-5) mol L(-1) CTAB at pH 1.2. Whereas the pH value of 3.7 were used for the individual determination of Sn(II) and Sn(IV) and also for total tin determination at the same conditions. Enrichment factors of 100 were obtained for the preconcentration of both metal ions. Under the optimal conditions, linearity was obeyed in the ranges of 55-670 microg L(-1) of Sn(II) and 46-750 microg L(-1) of Sn(IV) ion concentration. The detection limit of the method was also found to be 12.6 microg L(-1) for Sn(IV) and 8.4 microg L(-1) for Sn(II). The relative standard deviation of seven replicate determination of 100 microg L(-1) both metal ions were obtained about 2.4%. The diverse ion effect of some anions and cations on the extraction efficiency of target ions were tested. Finally, the optimized conditions developed were successfully utilized for the determination of each metal ion in various alloy, juice fruit, tape and waste water samples with satisfactory results.     

Catalytic effect of copper on the hexacyanoferrate(III)-cyanide redox reaction-II catalytic determination of copper

A catalytic method for the determination of copper, based on the catalysis of the hexacyano-ferrate(III)-cyanide redox reaction, is proposed. Experimental conditions to achieve the lowest detection limit are selected from the kinetics of both the catalysed and the uncatalysed reactions. The experimental measurements can be made at room temperature without close control. The rate-constant method is the most sensitive and precise, whereas the fixed-concentration and fixed-time methods appear to be the most rapid for routine analysis. A detection limit of 1.3 ng/ml and a coefficient of variation of about 3% for the determination of 63 ng/ml can be achieved. The catalytic effect of copper seems to be highly specific. Lead(II), bismuth (III), antimony (III), iron (II), iron(III), chromium(III), lanthanum(III), cerium(III), titanium(IV), zirconium(IV) and uranium(VI) interfere by precipitation. Species such as tin(II), cobalt(II), manganese(II), sulphite and thiosulphite cause serious interference because they react with hexacyanoferrate(III). Chromate interferes by its colour. Suitable methods to avoid the interferences from antimony(III), iron(III), chromium(III), titanium(IV), zirconium(IV), uranium(VI) and chromate are proposed.     

Thermochemical reactions of tin, lead, and antimony iodination in a small chamber electrode in determining metals by atomic emission spectrometry

Thermochemical reactions of tin, antimony, and lead iodination in a cavity of a small chamber electrode were studied. These reactions reduce the detection limits for analytes. It was shown that alkali and alkaline-earth metal iodides cannot be iodination agents. It was shown by spectrographic measurements that cadmium iodide mixed with carbon powder is the most efficient iodination agent. At the optimum conditions for analyte vaporization, the macrcomponents of the sample matrix (sodium, potassium, calcium, magnesium, aluminum, and iron) have almost no effect on the results of analysis. Based on the results obtained, a method was developed for determining tin, antimony, and lead in mineral stocks by atomic emission spectroscopy.     

Coulometric determination of microamounts of hydrogen in metal

Hydrogen in metal was extracted into a carrier gas (argon) by heating at about 1100 degrees , and oxidized to water with copper(II) oxide. The water was converted into ammonia with sodium amide at 80 degrees . The ammonia was then titrated with electrolytically generated hypobromite ion. The blank value of single determination could be reduced to less than 1 mug of water. Hydrogen in stainless steels, tantalum metal and pure tin metal could be determined satisfactorily, and some results were compared with those obtained by the ordinary vacuum extraction method.     

Structure of hydrated tin dioxide doped with Sb(III) ions

The effect of antimony doping of tin dioxide at Sb/Sn = 0.2–2.5 on the physical properties and structure of air-dry samples of hydrous tin dioxide, SnO₂ ? nH₂O (HTD), was studied by IR and Raman spectroscopy, powder X-ray diffraction, impedance measurements, TGA, and electron microscopy. The doped materials retained the structure of undoped HTD materials if the Sb/Sn ratio did not exceed the threshold value of 1.0. When Sb/Sn > 1, crystalline antimony oxide admixture appeared. The data of IR spectroscopy attested to the presence of two types of water in HTD-Sb, namely, physisorbed and chemisorbed water. The major part of water of the former type can be removed by evacuation at room temperature. Chemisorption occurs upon coordination of water molecules by metal ions through the formation of metal–oxygen bonds. Water molecules of the latter type are retained in evacuated samples at room temperature and on heating above the boiling point of liquid water. By impedance spectroscopy, HTD-Sb samples were shown to possess fairly high proton conductivity at high humidity; however, the conductivity decreased by two orders of magnitude after partial removal of water molecules of the former type. This attests to the destruction of the loosely bound hydrogen bond network, across which proton transfer takes place. It was also found that under conditions of constant humidity, the proton conductivity successively decreases with increasing antimony concentration. This is attributable to the fact that Sb(III) ions polarize the local environment to a lesser extent than Sn(IV) ions.     

Synthesis and structure of dithizonato complexes of antimony(III), copper(II) and tin(IV)

In view of the important role of dithizone in trace metal analyses, new structural aspects and approaches used to probe metal complexes of dithizone are of interest. Three X-ray diffraction structures are reported, dichloridobis(dithizonato)tin(IV), dichlorido(dithizonato)antimony(III), and bis(dithizonato)copper(II). During synthesis of the tin complex, auto-oxidation of Sn^IICl₂ to Sn^IV occurred without chloride liberation. The Sb^III complex revealed a unique distorted see-saw geometry which is, as for the other complexes, predicted by DFT molecular orbital calculations. The computed products of the lowest energy reactions are in agreement with experimentally obtained reaction products, which, together with molecular orbital renderings serve as a tool toward prediction of modes of coordination in these complexes. The S–M–N bond angle in the five-membered coordination ring shows a linear relationship with the corresponding metal ionic radii.     

Influence of tin(II) chloride on the solvent extraction of platinum group metals with N,N-di-n-hexyl-N'-benzoylthiourea

Summary The solvent extraction of Rh(III) and Pt(IV) with N,N-di-n-hexyl-N'-benzoylthiourea (DHBT)/toluene is substantially accelerated in the presence of tin(II) chloride. Low concentrations of SnCl₂ from 0.02 to 0.03 mol/l and metal/ligand ratio of 1:4 (Pt) resp. 1:9 (Rh) lead to low residual metal concentrations below the detection limit of GFAAS. The extraction behaviour of Pt(II), Ru(III) and Ir(III) is not affected by the treatment with SnCl₂.