A colorimetric determination of thorium

A colorimetric method for the determination of thorium is proposed. It is based upon the precipitation of thorium with a standard solution of oxalic acid and the subsequent reaction of the excess oxalic acid with a standard solution of potassium permanganate. The absorbancy of the remaining permanganate solution is directly proportional to the thorium present. The variables affecting this method have been critically studied. Reliable determinations can be made in the range of 3 to 30 mg of thorium in 1 cm cells when the colored solution is diluted to 250 ml. Most interfering substances can be removed by electrolysis in a mercury cathode cell or by the precipitation of thorium with potassium iodate.     

Controlled potential coulometric technique for the determination of thorium

A method based on controlled potential coulometry has been developed for the determination of thorium, using mercury as a working electrode. A known amount of EDTA is titrated coulometrically in the absence and in the presence of thorium. The difference in Coulombs obtained in these two titrations corresponds to the amount of thorium present in the aliquot. 0.5M sodium acetate has been used as a supporting electrolyte. Precision for thorium determination in the range of 4–8 mg is found to be better than ±0.2%.     

Amperometric complex-formation titration of traces of thorium

Thorium has been determined in the microgram range by complexometric titration with EDTA. The end-point was detected by following the anodic wave of EDTA at a rotating mercury electrode. It has been shown that thorium can be titrated in the presence of large amounts of other metals. Following electrolysis at a mercury pool electrode the titration is selective for thorium.     

Precipitation from homogeneous solution by photochemical action: determination of thorium

Thorium was precipitated from homogeneous solution by photochemical reduction of periodate to iodate in a solution containing thorium and perchloric acid, by means of a 2537 A low-pressure mercury vapour lamp. For weighing, the precipitate was redissolved, precipitated once as thorium hydroxide, and finally as thorium oxalate, which was ignited to thorium dioxide. Quantitative results were obtained in the range 35-180 mg of thorium.     

Extraction chromatographic separation of thorium (IV) with tri-n-octylphosphine oxide (TOPO)

Thorium was extracted from a mixture of nitric acid and NaNO₃ of 0.01M each at pH 2.2 on a column of silica gel coated with TOPO. Thorium was separated from alkalis, alkaline earths, chromium, iron, cobalt, nickel, zinc, cadmium, mercury, lead, trivalent rare earths, platinum group metals, chloride, phosphate and acetate in binary mixtures by selective extraction of thorium. Thorium was separated from cerium (IV), zirconium, uranium and molybdenum by selective elution of thorium with 0.01M H₂SO₄. The method was extended for the analysis of thorium in monozite ore.     

Studies on synthetic inorganic ion exchangers-V: preparation, properties and ion-exchange behaviour of amorphous and crystalline thorium tungstate

Amorphous and crystalline thorium tungstate have been prepared by mixing 0.1M thorium nitrate and 0.1M sodium tungstate under different conditions. The physico-chemical properties, chemical stability, composition, TGA, DTA, X-ray, infrared absorption and ion-exchange behaviour of thorium-tungstate are reported and discussed. Distribution coefficients of metal ions on thorium tungstate have been determined at pH 2-3 and 5.5-6.5. Selective ion-exchange separations of bismuth and mercury from other metal ions have been achieved on a column of thorium tungstate.     

Separations involving sulphides : Separation of thorium or titanium from some elements that form thiosalts

Sodium sulphide can be used to separate arsenic, antimony, tellurium, selenium, molybdenum, mercury, gold, platinum or rhenium from thorium and antimony, tellurium, selenium or mercury from titanium     

Formation of ferrocyanides-IV Th(IV), Nd(III), UO(2)(II) and Hg(II)

The stoichiometry of the reaction between ferrocyanide and thorium, neodymium, uranyl ion and mercury(II) has been investigated. The first three give single products irrespective of the order of addition of the reagents, but the last does not. If mercury(II) is added to ferrocyanide Hg(2)Fe(CN)(6) is obtained, but if ferrocyanide is added to mercury(II) various cyanide complexes of mercury are formed. The K(sp) values for the precipitates are reported.     

Electrochemical study of thorium in dimethylsulfoxide and propylene carbonate

Solutions of ThCl₄ in anhydrous dimethylsulfoxide or propylene carbonate have been investigated by dc polarography and controlled potential chronoamperometry on a hanging mercury drop electrode. The results are interpreted by assuming that the cathodic reduction of thorium on mercury proceeds through one step Th(IV)+4 e→Th(0) (E^1/2??1.65V vs. SCE in DMSO); however, the results obtained indicate that the reduction gives rise to the the formation of an autoinhibiting monoatomic layer of thorium; further reduction of thorium on this requires an overpotential (E^1/2??2.15 V vs. SCE in DMSO).The mean value for the maximal superficial concentration of thorium in the film deduced from these experiments equals 1.25×10^?9 mol cm^?2, whereas the value for a hexagonal close-packed layer is 1.5×10^?9 mol cm^?2.     

Back titration with mercuric nitrate in alkaline medium

Summary A rapid, reliable and accurate method for the determination of trivalent chromium, based on back titrating excess EDTA solutions in the presence of chromium versenate, with mercuric nitrate in alkaline media is given. By its aid amounts of chromium in the order of 50 micro- to 15 milligrams can be determined with fair accuracy. The method is applied for analysis of binary mixtures of chromium with thorium, copper(II), bismuth or mercury(II).     

Analytical aspects of some azo dyes from chromotropic acid

Summary Complexometric titration of thorium with di-sodium versenate solution has been carried out using three dyes: SNADNS, di-SNADNS and nitroso-SNADNS obtained from chromotropic acid. Determinations are suitable with these dyes in the p_H range from 2 to 3, the colour changes at the end point are very distinct with nitroso-SNADNS and di-SNADNS while the colour change with SNADNS at the end point is very difficult to detect. Study of interferences revealed that quite a number of elements like, lead, zinc, mercury, cobalt, nickel etc. do not interfere, whereas heavy interference is caused by iron, zirconium, copper, gold and alkaline earths, Thorium may be separated from them by precipitating it with phthalanilic acid obtained from o-anisidine and the thorium salt on breaking with acid may be determined by versene by the same method. This titrimetric method is expected to become more accurate if the final measurement at the end point is made spectrophotometrically rather than visually.     

Solid phase extraction of uranium and thorium on octadecyl bonded silica modified with Cyanex 302 from aqueous solutions

A simple and reliable method for rapid extraction and determination of uranium and thorium using octadecyl-bonded silica modified with Cyanex 302 is presented. Extraction efficiency and the influence of various parameters such as aqueous phase pH, flow rate of sample solution and amount of extractant has been investigated. The study showed that the extraction of uranium and thorium increase with increasing pH value and was found to be quantitative at pH 6; and the retention of ions was not affected significantly by the flow rate of sample solution. The extraction percent were found to be 89.55 and 86.27 % for uranium and thorium, respectively. The maximal capacity of the cartridges modified by 30 mg of Cyanex 302 was found to be 20 mg of uranium and thorium. The method was successfully applied to the extraction and determination of uranium and thorium in aqueous solutions. The percentage recovery of uranium and thorium in a number of natural as well as seawater samples of Iran were also investigated and found to be in the range of 85–95 %.     

Photochemical precipitation of thorium and cerium and their separation from other ions in aqueous solution

Thorium was precipitated from homogeneous solution by exposing solutions of thorium and periodate in dilute perchloric acid to 253.7 nm radiation from a low-pressure mercury lamp. Periodate is reduced photochemically to iodate which causes the formation of a dense precipitate of the basic iodate of thorium(IV). The precipitate was redissolved, the iodate reduced, the thorium precipitated first as the hydroxide, then as the oxalate and ignited to the dioxide for weighing. Thorium(IV) solutions containing 8-200 mg of ThO(2) gave quantitative results with a standard deviation (s) of 0.2 mg. Separations from 25 mg each of iron, calcium, magnesium, 50 mg of yttrium and up to 500 mg of uranium(VI) were quantitative (s = 0.25 mg). Separations from rare earths, except cerium, were accomplished by using hexamethylenetetramine rather than ammonia for the precipitation of the hydroxide. Cerium(III) was similarly precipitated and converted into CeO(2) for weighing. Quantitative results were obtained for 13-150 mg of CeO(2) with a standard deviation of 0.2 mg. Separations from 200 mg of uranium were quantitative. Other rare earths and yttrium interfered seriously. The precipitates of the basic cerium(IV) and thorium iodates obtained are more compact than those obtained by direct precipitation and can be handled easily. Attempts to duplicate Suzuki's method for separating cerium from neodymium and yttrium were not successful.     

Thenoyltrifluoroacetone as a reagent for cobalt

Summary An indirect method is proposed for the determination of cobalt (II) with 2-thenoyltrifluoroacetone at the milligram level. The orange cobalt-TTA chelate can be quantitatively precipitated over the p_H range 4.0–8.0. It is dissolved in acid and estimated as cobalt sulphate. Cobalt(II) can be estimated in presence of silver, mercury(II), strontium, iron(III), chromium (III), thorium, zirconium, uranium, citrate and tartrate. The method is reproducible to within ±1 per cent.     

The study of the distribution of arsenic, mercury, thorium, protactinium, uranium and neptunium under the ChemChar gasification process using radionuclide tracers

A experimental method to measure the fate and distribution of a variety of radionuclides under the ChemChar gasification process has been developed. The elements studied were arsenic, mercury, thorium, protactinium, uranium and neptunium. Results indicate that the ChemChar gasification system quantitatively retains these elements. In all of the cases except mercury the radiotracer was found to reside on the char matrix with small amounts (<1%) being found downstream in the condensation trap and char filter. Mercury, presumably as vapor, was entrained and distributed in significant amounts (≈40%) to the downstream char filter and its pre-filter. A methodology was developed to account for char height differences in quantifying the radiotracer on the char prior and subsequent to gasification. These results demonstrate the efficacy of using relatively short-lived radiotracers to characterize the behavior of hazardous elements during waste treatment via gasification.     

Stripping voltammetry of thorium based on adsorptive accumulation

A sensitive stripping voltammetric procedure for quantifying thorium is described. The chelate of thorium with the azo dye Mordant Blue 9 is adsorbed on the hanging mercury drop electrode, and the reduction current of the accumulated chelate is measured during a negative-going potential scan. Cyclic voltammetry is used to characterize the interfacial and redox behaviors. The effects of pH, dye concentration and accumulation potential are discussed. The detection limit is 4 × 10^?10 M (4-min accumulation), a linear current-concentration relationship is observed up to 1.3 × 10^?7 M, and the relative standard deviation (at the 6 × 10^?8 M level) is 3.1%. Possible interferences by trace metals and organic surfactants are investigated. Simultaneous quantitation of thorium and nickel is illustrated.     

新显色剂对-二甲氨基偶氮氯膦的合成及其与钍显色反应的研究

合成了新显色剂对-二甲氨基偶氮氯膦,研究了它与Th(Ⅳ)的显色反应.结果表明:Th(Ⅳ)在0～30μg/25mL范围内与该试剂形成的配合物在674,612和538nm³个波长处吸光度绝对值之和与溶液中Th(Ⅳ)的浓度呈线性关系,故可利用该3个波长下吸光度绝对值叠加的方法测定Th(Ⅳ),其ε值达1.74×10⁵L·mol^-1·cm^-1.由于显色反应在较强酸性介质中进行,本法有良好的选择性,大多数共存离子不干扰钍的测定,用于测定岩矿中的微量钍,结果满意.     

A precise,direct, heterometric micro-determination of mercury with diethyldithiocarbamate in excesses of metals ethylenediaminetetraacetate solutions

0.3–1.2 mg mercury in 20 ml aqueous solution is analysed with sodium diethyldithiocarbamate. The solution may contain any amount of other bivalent metal or iron (III), bismuth or thorium. A corresponding excess of ethylenediaminetetraacetate and ammonia must then be added. The error is 0–2%.     

Solid phase extraction and preconcentration of uranium(VI) and thorium(IV) on Duolite XAD761 prior to their inductively coupled plasma mass spectrometric determination

A simple and effective method is presented for the separation and preconcentration of thorium(IV) and uranium(VI) by solid phase extraction on Duolite XAD761 adsorption resin. Thorium(IV) and uranium(VI) 9-phenyl-3-fluorone chelates are formed and adsorbed onto the Duolite XAD761. Thorium(IV) and uranium(VI) are quantitatively eluted with 2 mol L⁻¹ HCl and determined by inductively coupled plasma-mass spectrometry (ICP-MS). The influences of analytical parameters including pH, amount of reagents, amount of Duolite XAD761 and sample volume, etc. were investigated on the recovery of analyte ions. The interference of a large number of anions and cations has been studied and the optimized conditions developed have been utilized for the trace determination of uranium and thorium. A preconcentration factor of 30 for uranium and thorium was achieved. The relative standard deviation (N = 10) was 2.3% for uranium and 4.5% for thorium ions for 10 replicate determinations in the solution containing 0.5 μg of uranium and thorium. The three sigma detection limits (N = 15) for thorium(IV) and uranium(VI) ions were found to be 4.5 and 6.3 ng L⁻¹, respectively. The developed solid phase extraction method was successively utilized for the determination of traces thorium(IV) and uranium(VI) in environmental samples by ICP-MS.