Conductometric studies on the precipitation of thorium hydroxide

This paper presents the effect of age on the conductance of hydroxide precipitated from thorium chloride with progressive addition of alkali. The effect of age on reverse titration has also been studied. Conductance study on the aged samples reveals that in every case there is at first a decrease in the electrical conductance of mixture and then an increase on prolonged ageing. This phenomenon is more marked with the concentrated solutions where it is presumed that adsorption of ions is more marked resulting in the diminution of electrical conductance. With dilute solutions, the precipitated mass being very small in amount does not adsorb appreciable amount of electrolytes from the system. On prolonged ageing there is a decrease of the surface reactivity of the precipitated mass, resulting in the release of adsorbed electrolytes and hence the increase in conductance of the system.

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Zusammenfassung Diese Arbeit behandelt die Wirkung der Alterung auf die Leitfähigkeit von Hydroxid, ausgefällt aus Thoriumchlorid mit fortschreitender Zufügung von Alkali. Auch der Alterungseinfluß auf den umgekehrten Vorgang: Zufügung von Thoriumchlorid zu Alkali, wurde untersucht. Die Leitfähigkeitsmessungen an gealterten Proben zeigen, daß zunächst stets eine Abnahme der elektrischen Leitfähigkeit der Mischungen und später eine Zunahme mit fortschreitender Alterung stattfindet. Dieses Phänomen ist für konzentriertere Lösungen ausgeprägter, bei denen ja wohl auch die Adsorption der Ionen stärker ist und damit die Abnahme der elektrischen Leitfähigkeit. Bei verdünnten Lösungen adsorbiert die dem Betrag nach sehr kleine ausgefällte Masse keine wesentlichen Beträge von Elektrolyten aus dem System. Mit verlängerter Alterung findet eine Abnahme der Oberflächenreaktivität des Fällproduktes statt, was die Freigabe von adsorbierten Elektrolyten und damit eine Zunahme der Leitfähigkeit des Systems zur Folge hat.

     

Conductometric studies on the precipitation of thorium hydroxide

The adsorption of stabilising ion H⁺ has been determined for a precipitate of hydrous ferric oxide and that of SO₄″ for the positively charged sol of hydrous ferric oxide during its coagulation as affected by potassium sulphate in presence of various non-electrolytes. The adsorption of both the stabilising and coagulating ions decreases in presence of ethyl alcohol and acetone, an increase is, however, observed in presence of glucose and urea. With gelatin at lower concentration the adsorption of both H⁺ and SO₄″ decreases whilst the reverse is noticed at higher concentrations. It is concluded that the cutting down of the adsorption of either the stabilising or the coagulating ion cannot explain sensitisation or stabilisation.     

Conductometric studies of DyCl3 in dilute aqueous solution

The limiting conductivity of Dy³⁺(aq) has been determined for the first time by linear extrapolation of conductivity measured in dilute aqueous solutions of (DyCl₃+HCl) at 25°C as ^o(Dy³⁺, aq) = (62.9±0.7) S-cm²-eq^-1. A second set of conductivity measurements in dilute aqueous solutions of DyCl₃ has given evidence of very slight hydrolysis of the cation, with a first hydrolysis constant of 6 x 10^–8 mol-dm^–3 (pK=7.2±0.5) calculated by applying the Onsager-Kim law of electrolyte mixtures.     

Complexometric estimation of thorium

Summary Thorium has been determined by titration with EDTA (disodium salt) solution as complexometric reagent at p_H 3–4.5 using a drop of 0.01 M iron(III) solution mixed with thiocyanate-p-anisidine as indicator. Calcium, barium, strontium, magnesium or manganese ions do not interfere, but zinc, zirconium, lead, silver, aluminium, bismuth, phosphate, fluoride or oxalate ions interfere in this estimation. In these complexometric titrations the quantitative results obtained by using a drop of iron(III) solution mixed with thiocyanate-p-anisidine as indicator are comparable with those obtained with pyrocatechol violet indicator.

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Zusammenfassung Thorium wird bei p_H 4–4,5 mit ÄDTA titriert, wobei ein Gemisch eines Tropfens Eisen(III)-lösung mit Thiocyanat-p-Anisidinlösung als Indicator dient. Calcium, Barium, Strontium, Magnesium oder Mangan verursachen keine Störung, wogegen folgende Ionen stören: Zink, Zirkonium, Blei, Silber, Aluminium, Wismut, Phosphat, Fluorid oder Oxalat. Der erwähnte Mischindicator liefert ähnlich genaue Titrationsergebnisse wie bei Verwendung von Brenzcatechinviolett als Indicator.

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The authors take this opportunity to thank the Council of Scientific and Industrial Research (India) for the award of Junior Fellowship to one of them (junior author). This has enabled us to pursue the study of complexometric titrations.     

Potentiometric estimation of thorium as oxalate

Summary The potentiometric determination of thorium as oxalate yields values with a constant error and therefore can be employed for analysis with a suitable correction.

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Zusammenfassung Die potentiometrische Thoriumbestimmung als Oxalat liefert Werte mit konstantem Fehler und kann daher mit entsprechender Korrektur zur Analyse verwendet werden.

     

Colorimetric estimation of thorium with carmine red

The use of carmine red as a colorimetric reagent for thorium in presence of a 20 fold excess of cerite earths or a 5 fold excess of uranyl salts is described, p_H of 2.5 and the wavelength 560 m were found most suitable. The ratio of thorium to reagent in the complex is shown to be 14 from spectrophotometric data. It is also shown that the complex dissociates little under these conditions.     

Gravimetric estimation of thorium with N-phenylanthranilic acid

Summary From nitric or hydrochloric acid medium thorium is quantitatively precipitated by N-phenylanthranilic acid in the range of pH 1.5–3.4 as a light yellow compound, which can be dried to a definite composition, Th(C₁₃H₁₀NO₂)₄, at 110° C. This has been utilized for the direct gravimetric estimation of thorium and its separation from uranium(VI), cerium(III), aluminium and iron at a pH of ca. 2.0–2.5.This method is superior to most of the existing methods for the estimation of thorium since quantitative precipitation occurs at a relatively low pH and the thorium compound, which has a high molecular weight, can be weighed directly, thus making possible the determination of rather small quantities (ca. 5 mg) of thorium with fair accuracy (error less than 1%).

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Zusammenfassung Thorium kann aus salpeter-oder salzsaurer Lösung im pH-Bereich 1,5–3,4 mit Hilfe von N-Phenylanthranilsäure als hellgelber Niederschlag quantitativ ausgefällt werden. Der Mederschlag kann bei 110°C zu definierter Zusammensetzung getrocknet werden [Th(C₁₃H₁₀NO₂)₄]. Diese Fällung wurde zur direkten gravimetrischen Bestimmung von Thorium und seiner Trennung von Uran(VI), Cer(III), Aluminium und Eisen bei pH 2,0–2,5 benutzt. Das Verfahren ist den meisten bekannten Methoden überlegen, das die Fällung bei relativ niedrigem pH durchgeführt und die Thoriumverbindung (die ein hohes Molekulargewicht hat) direkt gewogen werden kann. Kleine Mengen Thorium (etwa 5 mg) können mit recht guter Genauigkeit bestimmt werden (Fehler kleiner als 1%).

     

Preparation of thorium concentrate from concentrated calcium chloride solutions

Extraction, washing, back extraction, and precipitation of Th(IV) from the backwash in the hydrochloric acid processing of perovskite are studied. Process conditions are optimized to obtain a concentrate with a ThO₂ content of about 85 wt %.     

Back titration with mercuric nitrate in alkaline medium potentiometric estimation of thorium

Summary Mercuric nitrate has proved to be a suitable back titrant for EDTA amounts in excess of those reacting quantitatively with thorium amounts ranging from 46 g up to 25 mg. End points are detected potentiometrically with reasonable jumps amounting to an average of 70 mV per 0.1 ml titrant. Thorium can be determined with fair accuracy, in the presence of double its amount of uranium.     

The electrolytic separation from thorium nitrate of thorium c (212Bi) and thorium b (212Pb) in chloride solution

An electrodeposition process is described for separating thorium C and thorium B from radio-chemically “old” samples of thorium nitrate in hot 0.5N hydrochloric acid solution. The thorium C is first deposited on either platinum or nickel cathodes of special design using a controlled potential at the cathode, followed by the deposition of thorium B. Weights of the order of 10^-15 g ThC are involved.     

X-ray scattering reveals ion clustering of dilute chromium species in molten chloride medium

Enhancing the solar energy storage and power delivery afforded by emerging molten salt-based technologies requires a fundamental understanding of the complex interplay between structure and dynamics of the ions in the high-temperature media. Here we report results from a comprehensive study integrating synchrotron X-ray scattering experiments, ab initio molecular dynamics simulations and rate theory concepts to investigate the behavior of dilute Cr³⁺ metal ions in a molten KCl–MgCl₂ salt. Our analysis of experimental results assisted by a hybrid transition state-Marcus theory model reveals unexpected clustering of chromium species leading to the formation of persistent octahedral Cr–Cr dimers in the high-temperature low Cr³⁺ concentration melt. Furthermore, our integrated approach shows that dynamical processes in the molten salt system are primarily governed by the charge density of the constituent ions, with Cr³⁺ exhibiting the slowest short-time dynamics. These findings challenge several assumptions regarding specific ionic interactions and transport in molten salts, where aggregation of dilute species is not statistically expected, particularly at high temperature.

Ion clustering of dilute chromium species was unexpectedly revealed in a high-temperature molten chloride salt, challenging several long-held assumptions regarding specific ionic interactions and transport in molten ionic media.     

Coordination around thorium(IV) in aqueous perchlorate,chloride and nitrate solutions

The coordination around the thorium(IV) ion in aqueous perchlorate, chloride and nitrate solutions has been determined from large angle X-ray scattering measurements. In perchlorate solutions, where inner-sphere complexes are not formed, the first coordination sphere contains 8.0±0.5 water molecules with Th-H₂O bond lengths of 2.48₅ Å. In chloride solutions inner-sphere complexes are formed, which lead to an increase in the coordination number. In nitrate solutions the nitrate ions are bonded as bidentate ligands to the thorium ion. The bond lengths are similar to those found in crystalline hydrates of thorium nitrate. The coordination numbers found for thorium(IV) in solution are compared with previously reported values for lower charged ions of similar size.On leave from Department of Inorganic Chemistry Royal Institute of Technology S-10044 Stockholm Sweden     

Viscosity-temperature relationships for poly(vinyl chloride)-tetrahydrofuran dilute solutions

The viscous flow parameters for dilute PVC tetrahydrofuran solutions were determined in the temperature range 10–45°. The temperature dependence of the viscosity of the solutions obeys an Arrhenius-type equation. The concentration and the molecular weight dependence of the pre exponential factor of this equation is given by the following relationship:

$\text{A=A}{}_0\text{·}\text{exp}\text{[minus;K}{}_{\mathrm{a}}\text{(c·}\text{M}{}_{\mathrm{w}}\text{)}{}^2\text{]}$

.Both the values of the viscous flow parameters and the mathematical expression of the pre-exponential factor indicate, by comparison with other results, some stiffness of PVC chains in tetrahydrofuran.     

Spectrophotometric estimation of bromide ion in excess chloride media

The redox reaction between bromate and chloride ions in the presence and the absence of two or less equivalents of bromide ion ascertaining the formation of bromine chloride species of type BrCl and BrCl₂⁻ in subsequent reactions in 4% H₂SO₄, has been studied by spectrophotometry. Calibration graphs for the bromide ion estimation in 0.1% KBrO₃–4% H₂SO₄ medium are determined separately in the presence of known amounts of NaCl. The effect of Cl⁻ ion percentage on the determination of Br⁻ ion is studied and reported herewith a suitable equation for a precise, reliable and quick spectrophotometric estimation.     

Coordination chemistry of trivalent lanthanide and actinide ions in dilute and concentrated chloride solutions

We have used EXAFS spectroscopy to investigate the inner sphere coordination of trivalent lanthanide (Ln) and actinide (An) ions in aqueous solutions as a function of increasing chloride concentration. At low chloride concentration, the hydration numbers and corresponding Ln,An-O bond lengths are as follows: La3+, N = 9.2, R = 2.54 A; Ce3+, N = 9.3, R = 2.52 A; Nd3+, N = 9.5, R = 2.49 A; Eu3+, N = 9.3, R = 2.43 A; Yb3+, N = 8.7, R = 2.32 A; Y3+, N = 9.7, R = 2.36 A; Am3+, N = 10.3, R = 2.48 A; Cm3+, N = 10.2, R = 2.45 A. In ca. 14 M LiCl, the early Ln3+ ions (La, Ce, Nd, and Eu) show inner sphere Cl- complexation along with a loss of H2O. The average chloride coordination numbers and Ln-Cl bond lengths are as follows: La3+, N = 2.1, R = 2.92 A; Ce3+, N = 1.8, R = 2.89 A; Nd3+, N = 1.9, R = 2.85 A; Eu3+, N = 1.1, R = 2.81 A. The extent of Cl- ion complexation decreases going across the Ln3+ series to the point where Yb3+ shows no Cl- complexation and no loss of coordinated water molecules. The actinide ions, Am3+ and Cm3+, show the same structural effects as the early Ln3+ ions, i.e., Cl- ion replacement of the H2O at high chloride thermodynamic activities. The Clion coordination numbers and An-Cl bond lengths are: Am3+, N = 1.8, R = 2.81 A; Cm3+, N = 2.4, R = 2.76 A. When combined with results reported previously for Pu3+ which showed no significant chloride complexation in 12 M LiCl, these results suggest that the extent of chloride complexation is increasing across the An3+ series. The origin of the differences in chloride complex formation between the Ln3+ and An3+ ions and the relevance to earlier work is discussed.     

The conductivity of dilute aqueous solutions of magnesium chloride at 25°C

There is a disagreement in the literature regarding the best value of _o[1/2MgCl₂]. For this reason, the conductivity of dilute aqueous MgCl₂ solutions have been determined at 25°C. The new experimental data and those available in the literature have been analyzed with two theoretical treatments of electrolytic conductivity. On the basis of that analysis, the values 129.72±0.05 and 53.40±0.05 S-cm²-mol^–1 for _o[1/2MgCl₂] and _o[1/2Mg²⁺], respectively, are recommended.     

A sensitive two-phase titration of anionic surfactants with a dilute tetraphenylphosphonium chloride solution

A visual indicator method is described for titrations of anionic surfactants with 5 × 10^-5 M tetraphenylphosphonium solution. Two dyes, the hydrophilic neutral red and the hydrophobic tetrabromophenolphthalein ethyl ester, are used as indicator in the presence of 1,2-dichloroethane.