Thallimetric oxidations-VI Titrimetric and spectrophotometric methods for the determination of phosphite and analysis of binary mixtures of phosphite and oxalate

Titrimetric and spectrophotometric methods have been developed for the estimation of phosphite at mmole and mumole levels, respectively. Thallium(III) is used as an oxidant and the thallium(I) produced is determined either oxidimetrically with potassium bromate or by measurement of the absorbance of thallium(III) at 260 nm in the presence of 0.1 M hydrochloric acid and 1 M perchloric acid. Based on the fact that phosphite and oxalate are oxidized under different conditions, methods are described for the analysis of binary mixtures of phosphite and oxalate. A method is also described for estimation of thallium(III) with phosphite as reluctant, and is applied for analysis of mixtures of thallium(I) and thallium(III).     

Thallimetric oxidations-V Titrimetric and spectrophotometric determination of hydrogen peroxide

Titrimetric and spectrophotometric methods have been developed for the determination of hydrogen peroxide at mmole and mumole levels respectively. In these methods thallium(III) is used as the oxidant and the reduced thallium(I) is determined oxidimetrically with potassium bromate in the titrimetric method and by measuring the absorbance of thallium(III) at 260 nm in the presence of 0.1M hydrochloric acid and 1M perchloric acid in the spectrophotometric method. Photochemical redox methods for the estimation of hydrogen peroxide in the presence of a number of diverse ions are described.     

Determination of thallium(III) by use of a mercury reductor

A convenient method has been developed for the determination of thallium(III) by using a mercury reductor. Thallium(III) is reduced to thallium(I) in 0.5–4N hydrochloric or sulphuric acid medium and the determination is completed by oxidative titration with potassium bromate. The method is extended to analysis of thallium(III)-thallium(I) and thallium(III)-iron(III) mixtures.     

Solvent extraction and separation of gallium, indium and thallium with N-benzylaniline

A simple and rapid method is proposed for the separation of tervalent gallium, indium and thallium by solvent extraction with N-benzylaniline in chloroform from different concentrations of hydrochloric acid. Thallium and gallium are extracted from 1M and 7.0-7.5M hydrochloric acid respectively. Indium is finally extracted from hydriodic acid. These metals in the final extracts are determined complexometrically. Interference from some cations can easily be eliminated by reduction with sulphite, followed by selective oxidation of thallium(I) to thallium(III) with saturated bromine water, and from others by the use of thioglycollic acid as a masking agent in the extraction of gallium and indium. Most common anions cause no interference. Log-log plots of distribution coefficients vs. concentration of amine for gallium, indium and thallium indicate a 2:1 limiting mole ratio of amine to these metals.     

Rearrangement of the Binuclear K4Mo2Cl8 Cluster Structure in the Process of Its Oxidation in HCl Solution

Russian Journal of General Chemistry - Batch-type spectroscopic and continuous potentiometric titration of K4Mo2Cl8 with potassium dichromate in 1 M hydrochloric acid was carried out. Intermediate...     

Thallimetric oxidations-IV Estimation of malonic acid

Malonic acid is quantitatively oxidized to carbon dioxide and water when refluxed for 120 min in sulphuric acid medium (concentration 1.5M) with at least four times as much thallium(III) as that stoichiometrically required for complete oxidation. The thallium(I) formed is estimated bromatometrically in the presence of 1.5-2M hydrochloric acid, with Methyl Orange as indicator. The indicator correction is negligible. The relative mean deviation is 0.2%. Possible side-reactions and their suppression are discussed.     

Spectrophotometric determination of bismuth in concentrates and non-ferrous alloys by the iodide method after separations by diethyldithiocarbamate and xanthate extraction

A method for determining 0.0001-1% of bismuth in copper, molybdenum, lead, zinc and nickel sulphide concentrates is described. After sample decomposition, bismuth is separated from matrix and other elements, except lead and thallium(III), by chloroform extraction of its diethyldithiocarbamate complex, pH 11.5-12.0, from a sodium hydroxide medium containing citric acid, tartaric acid, EDTA and potassium cyanide as complexing agents. Following back-extraction of bismuth into 12M hydrochloric acid and reduction of thallium to the univalent state, bismuth is separated from co-extracted lead and thallium by chloroform extraction of its xanthate from a 2.5M hydrochloric acid-tartaric acid-ammonium chloride medium. Bismuth is then determined spectrophotometrically, at 337 or 460 nm, as the iodide. Interference from lead, which is co-extracted in mug-amounts as the xanthate and causes high results at 337 nm, is eliminated by washing the extract with a hydrochloric acid solution of the same composition as the medium used for extraction. The proposed method is also applicable to lead-, tin- and copper-base alloys.     

Extraction-spectrophotometric determination of thallium in high-purity indium

Trace amounts of thallium in high-purity indium are separated from the matrix by extraction from 6M hydrochloric acid by di-isopropyl ether. On shaking the extract with Brilliant Green in 0.15M hydrochloric acid, an ion-association complex is formed in the organic phase. Interference of other elements is removed by their reduction with metallic copper and scrubbing. The proposed method permits determination of 10(-5)-10(-6)% thallium in high-purity indium with good precision and accuracy.     

Chemical analysis of manganese nodules: Part III. Determination of Thallium,Molybdenum and Vanadium after Anion-Exchange Separation

A method is described for the determination of thallium, molybdenum and vanadium in manganese nodules. After dissolution of the sample in a mixture of perchloric and hydrofluoric acids, thallium and molybdenum are adsorbed on the strongly basic anion-exchange resin Dowex 1 (chloride form) from 6 M hydrochloric acid containing bromine. Molybdenum is eluted with 2 M perchloric acid-1 M hydrochloric acid and determined by a.a.s. with a nitrous oxide—acetylene flame. Thallium is eluted with an aqueous solution of sulphur dioxide and, after evaporation of the eluate, this element is determined by a.a.s. with an air—acetylene flame. The same method is used for the assay of vanadium in the 6 M hydrochloric acid effluent. The method was used successfully for the determination of thallium, molybdenum and vanadium at the ppm level in numerous samples of nodules from the Pacific Ocean and Lake Michigan.     

Precise determination of uranium in pure uranium and uranium compounds by constant-current coulomeric titration

A procedure is described for very precise determination of uranium in high-purity uranium and uranium compounds. Uranium(VI) is reduced in a concentrated hydrochloric acid solution by metallic aluminium in the presence of cadmium ions to uranium(III). This is oxidized to uranium(IV) by protons on addition of an excess of orthophosphoric acid, and then oxidized to uranium(VI) by adding a weighed quantity of potassium dichromate in small excess. The excess of potassium dichromate is determined by constant-current coulometry. The coefficient of variation does not exceed 0.003%.     

黄钠铁矾中铁的测定

准确快速测定黄钠铁矾中铁的含量有利于控制铁湿法冶金的流程。采用氢氧化钠溶液分解试样,盐酸(1+9)溶解滤渣,蒸发除过量酸,氨水沉淀分离铜、镍、钴等元素,再用稀盐酸溶解沉淀。在盐酸介质中,SnCl_2将大部分Fe(Ⅲ)还原为Fe(Ⅱ),钨酸钠为指示剂,用TiCl_3还原呈钨蓝色,重铬酸钾滴定至蓝色褪去。再以二苯胺磺酸钠为指示剂,重铬酸钾标准溶液滴定测定样品中铁的含量。实验表明,黄钠铁矾中共存干扰元素绝大部分被分离,同时与酸溶解法进行比较,测定数据一致,相对标准偏差(n=9)小于0.1%。     

Photochemical thallimetric oxidations-estimation of formic acid

A simple, rapid and convenient redox method has been developed for the estimation of formic acid. Formic acid is photochemically oxidized with thallium(III) in the presence of bromide as catalyst, and the thallium(I) formed is determined by titration with potassium bromate. The procedure can also be used for the estimation of thallium(III) with formic acid as reductant.     

Sodium hypochlorite as volumetric reagent

Summary In presence of 5 N to 6 N hydrochloric acid, ferrous ethylenediamine sulphate was used as a reducing agent to determine indirectly potassium chlorate, potassium bromate, potassium metaperiodate, potassium dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide, ceric sulphate and chloramine-T. An excess of ferrous ethylenediamine sulphate added to each of the substances in the acid medium was titrated with a standard solution of sodium hypochlorite. Iodine monochloride was used as catalyst and preoxidizer and chloroform was used as an indicator. Chloroform was coloured violet owing to the liberation of iodine during the titration and became very pale yellow at the end-point because of the formation of iodine monochloride.Part I: See Z. analyt. Chem. 160, 429 (1958).     

Separation of uranium(VI) as chloride complex by solvent extraction with dicyclohexyl-18-crown-6

Uranium(VI) was quantitatively extracted from 6 to 8M hydrochloric acid with 0.02M DC-18-crown-6 in chloroform. It was stripped from the organic phase with 0.5M hydrochloric acid and determined as its Arsenazo-III complex at 665 nm. Uranium(VI) was separated from several elements such as thorium, zirconium, scandium, yttrium, thallium and tin in complex mixtures. The method was extended for analysis of uranium in monazite and rock sample.     

A new oxidimetric reagent: potassium dichromate in a strong phosphoric acid medium-VI Potentiometric titration of vanadium(III) alone and in mixture with vanadium(IV)

Vanadium(III) can be titrated at room temperature with potassium dichromate in an 8-12M phosphoric acid medium. Two potential breaks are observed in 12M phosphoric add with 0.2N potassium dichromate, the first corresponding to the oxidation of vanadium(III) to vanadium(IV) and the second to the oxidation of vanadium(IV) to vanadium(V). In titrations with 0.05N dichromate only the first break in potential is clearly observed. The method has been extended to the titration of mixtures of vanadium(III) and vanadium(IV). Conditions have also been found for the visual titration of vanadium(III) using ferroln or barium diphenylamine sulphonate as indicator.     

Pollution-free method for the determination of iron in iron ore

A method for the determination of total iron in iron ores and concentrates is described which avoids the use of mercuric chloride. The sample is decomposed either by an acid attack or by fusion with sodium peroxide. The hot sample solution in about 6M hydrochloric acid is treated with hot 10% stannous chloride solution till pale yellow, followed by addition of a slight excess of 2% titanous chloride solution; the excess is then oxidized with perchloric acid (1 + 1). The solution is rapidly cooled in ice-water, and the iron (II) is titrated with potassium dichromate (sodium diphenylsulphonate as indicator). The results show the same degree of precision, accuracy, and degree of interference as those obtained by the standard stannous chloride-mercuric chloride method.     

Determination of iodide with potassium dichromate and sodium vanadate in the presence of acetone

The determination of iodide with potassium dichromate and sodium vanadate in 6-8M phosphoric acid medium by potentiometric or visual titration is described. Ferroin and barium diphenylamine sulphonate (BDAS) are used as the indicators in the visual titration with potassium dichromate and sodium vanadate respectively. Acetone is used to stabilize the iodonium ions liberated, in the visual titration. Iodide can also be determined with sodium vanadate in 2-4M sulphuric acid medium with BDAS as indicator in the presence of oxalic acid as catalyst and acetone to stabilize the liberated iodine cations. The visual procedures are applied for the determination of iodide in tincture of iodine. The formal potentials of the iodine/iodide couple in various phosphoric acid media are reported.     

The determination of metallic iron in the presence of fayalite

In a proposed new procedure the sample is treated with bromine, the excess of bromine removed, and the residue extracted with methanol. After filtration the filtrate is evaporated to remove methanol and the bromides are dissolved in hydrochloric acid for determination of metallic iron. The oxide residue from the filtration is fused in sodium peroxide and then dissolved in hydrochloric acid for the determination of iron present either as oxide or silicate. Iron in the hydrochloric acid solutions from the residue and filtrate is determined either by titration with standard potassium dichromate solution or by atomic-absorption spectrometry.     

Separation of traces and larger amounts of bismuth from gram amounts of thallium, mercury, gold and platinum by cation-exchange chromatography on a macroporous resin

Traces and larger amounts of bismuth (up to 50 mg) can be separated from gram amounts of thallium, mercury, gold and platinum (up to 5 g) by sorption from a mixture of 0.1M hydrochloric acid and 0.4M nitric acid on a column containing just 3 g (8.1 ml) of AGMP-50, a macroporous cation-exchange resin. This resin retains bismuth much more strongly than does the usual microporous resin (styrene-DVB with 8% cross-linkage). Other elements are eluted with the same acid mixture as that used for sorption, and bismuth is finally eluted with 1.0M hydrochloric acid. Separations of bismuth are sharp and recoveries quantitative. Only microgram amounts of the other elements remain in the bismuth fraction. Amounts of bismuth as little as 5 mug have been separated from 5 g of thallium, and determined (r.s.d. = 2%) by flame atomic-absorption. Only 100-mug amounts of bismuth have been separated from gram amounts of mercury, gold, and platinum, but there is no reason to believe that smaller or larger amounts of bismuth cannot be separated from these elements and recovered with the same accuracy as that for the separation from thallium. The lower limit of the method is determination of 0.4 mug of bismuth in 10 ml of solution (0.004 absorbance). An elution curve, the relevant distribution coefficients and the results of analysis of synthetic mixtures and two practical samples [thallium metal and mercury(II) nitrate] are presented.     

Subject index

Thermal decomposition of an intimate mixture of thallium(I) perchlorate and chromium(III) oxide revealed that chromium(III) oxide lowers the decomposition temperature of thallium(I) perchlorate and is oxidized into hexavalent state to give thallium(I) dichromate. The thermal decomposition was followed by constant temperature heating, thermogravimetry and differential thermal analysis. The reaction products were characterized by chemical analysis, X-ray diffraction and infrared spectral measurements.