Development of a method for recovery of 233U from thorium oxalate cake in reconversion step of reprocessing of irradiated thorium rods

A method is developed for the selective leaching of ²³³U from a thorium oxalate cake. The leaching capacity of ammonium carbonate and nitric acid have been investigated, showing that (NH₄)₂CO₃ leads to higher recovery. The maximum leaching efficiency is obtained using 0.5% ammonium carbonate, with a minimal thorium pick-up. A uranium recovery of 94% is obtained after three consecutive contact experiments in carbonate media, with minimal thorium uptake in the leachate. This process was applied to an actual plant stream, allowing the reduction of the ²³³U -activity from 5.64 to 0.3 Ci/g of thorium oxalate cake.     

Nickel phthalocyanine sulphonic acid as a redox indicator in cerimetry

Summary The use of nickel phthalocyanine sulphonic acid (Ni-PS) as an internal indicator in the cerimetric titration of iron(II) has been investigated. 0.2 ml of a 0.05% solution of the dye serves well as a redox indicator in 50 ml of the titration mixture. The colour change at the end point is from blue to violet. The addition of about 2.5 ml of syrupy phosphoric acid to 50 ml of the titration mixture has been found to be advantageous as it increases the life period of the violet coloured transitory oxidation product of Ni-PS. The Ni-PS indicator is superior to the Cu-PTS indicator previously reported, in that the intermediate violet oxidation product obtained with the former at the equivalence point has a longer life period.It has been observed that in the cerimetric titration of 3–8 ml of about 0.1 N uranium(IV) diluted to 50 ml, the equivalence point is marked by a colour change from turquois blue to colourless, without the appearance of any intermediate violet colour. However, the intermediate violet colour appears, if 3 ml of syrupy phosphoric acid is added before the start of the titration. In the titration of more dilute solutions of uranium(IV) the indicator gives premature and hazy end points. How-ever, in the presence of phosphoric acid, correct equivalence points are obtained.The cerimetric titration of molybdenum(V) using Ni-PS as indicator is recommended to be carried out in 2 N sulphuric acid medium. The addition of phosphoric acid is not necessary. The colour change at the equivalence point is from turquois blue to violet which is stable for 10–15 sec.

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Zusammenfassung Nickel-phthalocyanin-sulfonsäure (NPS) kann als Indicator bei der cerimetrischen Titration von Eisen(II), Uran(IV) und Molybdän(V) mit gutem Erfolg verwendet werden. Auf 50 ml Titrationslösung benötigt man 0,2 ml einer 0,05%igen Lösung des Indicators. Der Farbumschlag am Endpunkt erfolgt von Blau nach Violett. Ein Zusatz von 2,5 ml sirupöser Phosphorsäure auf 50 ml Lösung ist vorteilhaft, da er die Lebensdauer des violett gefärbten Zwischenproduktes der Oxydation von NPS erhöht. Der NPS-Indicator ist wegen der längeren Beständigkeit des erwähnten Zwischenproduktes der früher beschriebenen Kupferphthalocyanin-tetrasulfonsäure überlegen.Bei der cerimetrischen Titration von 3–8 ml ungefähr 0,1 n Uran (IV)-lösung, die auf 50 ml verdünnt wurde, erhält man einen Farbumschlag von Türkisblau nach Farblos, ohne daß das Violett gefärbte Zwischen-produkt auftritt. Wenn man jedoch vor der Titration 3 ml sirupöse Phosphorsäure zusetzt, so erscheint die violette Farbe. Bei der Titration verdünnterer Lösungen ergeben sich vorzeitige und unklare Farbum-schläge. Doch führt auch hier ein Zusatz von Phosphorsäure zu richtigen Werten.Die Titration von Molybdän (V) mit dem beschriebenen Indicator wird am besten in 2n schwefelsaurer Lösung ausgeführt, wobei ein Phosphorsäurezusatz nicht erforderlich ist. Der Farbumschlag erfolgt von Türkisblau nach Violett (Beständigkeit 10–15 sec).

     

Aqueous polymerization of acrylonitrile by ascorbic acid–peroxodisulfate redox system

The polymerization of acrylonitrile initiated by an ascorbic acid–peroxodisulfate redox system was studied in an aqueous solution at 35°C in the presence of air. Molecular oxygen was found to have no effect on the polymerization reaction. An increase in ionic strength slightly increased the rate. The overall rate of polymerization, R_p, showed a square dependence on [monomer] and a half-order dependence on [peroxodisulfate]. A first-order dependence on [ascorbic acid] at low concentrations (<3.0 × 10^?3 mol L^?1) followed by a decrease in R_p at higher concentrations of ascorbic acid (>3.0 × 10^?3 mol L^?1) was also noted. R_p remained unchanged up to 40°C and showed a decline thereafter. Addition of catalytic amounts of cupric ions decreased the rate whereas ferric ions were found to increase the rate. Added sulfuric acid in the range (6.0?50.0) × 10^?5 mol L^?1 decreased the R_p.     

A potentiometric study of the oxidation of cobalt(II) with gold(III) chloride in presence of 1,10 phenanthroline or 2,2'-bipyridine : A new titration of cobalt (II) and its application to nickel-base alloys

The redox reaction between cobalt(II) and gold(III) chloride in the presence of 1.10-phenanthroline or 2,2'-bipyridine was studied, and a titration of the cobalt(II) complex with a gold(III) chloride solution was developed. A 4-fold amount of 1,10-phenanthroline or 2,2'-bipyridine was necessary for rapid quantitative reaction; the permissible pH range was 1.5–5. The oxidation of the cobalt(II) complex proceeds rapidly at 40–50°C, and a direct potentiometric titration was possible. The following maximum errors were obtained: 3.3% for 0.2–1.0 mg Co, 2.0% for 1–5 mg Co, and 0.70% for 10–40 mg Co. The following ions did not interfere: Ni(II), Zn(II), Pb(II), Cd(II), Mn(II), Fe(II), Cr(III), Al(III), Th(IV), Se(IV), Ti(IV), U(VI), Mo(VI), SO^2-₄ and PO^3-₄. Even small quantities of silver(I), copper(II), palladium(II), mercury(II)and iron(III) interfered. The method was applied to the determination of high cobalt contents in high-temperature nickel-base alloys.     

Validated Chiral LC Method for the Enantiomeric Separation of β-Amino-β-(3-Methoxyphenyl) Propionic Acid

A chiral liquid chromatographic method for enantiomeric resolution of β-amino-β-(3-methoxyphenyl) propionic acid was developed and validated. The “hybrid” π-electron donor–acceptor based stationary phase (R,R) Whelk-01 was found to be enantiomerically selective for (R) and (S) enantiomers of β-amino-β-(3-methoxyphenyl) propionic acid with a resolution greater than 2.0. The effects of isopropyl alcohol and ethanol on enantioselectivity and resolution of enantiomers were evaluated. Calibration curves were linear over the range of 0.10–1.00, with a regression coefficient (r) of 0.999. The limit of detection (LOD) and limit of quantification (LOQ) were 300 and 1,000 ng mL⁻¹ respectively for 10 μL injection volume. The percentage RSD of the peak area of six replicate injections of (S) enantiomer at LOQ concentration was 2.8. The percentage recovery of (S) enantiomer from (R) enantiomer samples ranged from 92 to 102. The test solution was observed to be stable up to 24 h after the preparation. The developed normal phase chiral LC method can be used for the enantiomeric purity evaluation of R-β-amino-β-(3-methoxyphenyl) propionic acid.     

Micellar effect of sodium dodecyl sulfate on the reactions between iron(II) and p-benzoquinone, and iron(III) and hydroquinone

The micellar effet of sodium dodecyl sulfate (SDS) on the initial stages of the reaction between (1) Fe(II) and p-benzoquinone, and (2) Fe(III) and hydroquinone have been investigated. In the former case acceleration was observed, the rate-[surfactant] profile showing a maximum. SDS has an inhibitory effect on the latter reaction. Kinetic analysis has been carried out using Berezin's approach.

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() 1) Fe(II) 2) Fe(III) . - . . , .

     

The chemistry of cyclic enaminoketones. III. Synthesis of bi- and tricyclic enaminoketones from enamine esters and nitriles

The cyclization of enamines derived from β-aminoesters and β-aminonitriles into bi- and tricyclic enaminoketones ( 6,9,13 and 24 ) has been investigated. The enamines derived from aminonitriles cyclize smoothly with magnesium perchlorate in benzene or toluene, whereas the enamines derived from aminoesters cyclize spontaneously during their formation. The scope and limitation of this process is discussed.