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  • Author or Editor: G. Rama Rao x
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Abstract  

Studies on the individual potentiometric determination of uranium and plutonium in a single aliquot have been initiated recently in our laboratory. It was required to adapt the reported procedures (for the precise determination of uranium and plutonium individually when present together in a sample) at various stages to make them suitable for the successive application of the procedures to the same aliquot. Two alternative schemes are proposed in the present work. In the first, plutonium is determined by HClO4 oxidation followed by the determination of total uranium and plutonium by Zn(Hg) reduction. In the second, plutonium is determined by AgO oxidation following the determination of total uranium and plutonium by Zn(Hg) reduction. Amount of uranium is computed in both cases from the difference of two determinations. Precision for the assay of plutonium and uranium was found to be ±0.25% and ±0.35%, respectively, at milligram levels.

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Abstract  

Several adducts of U(IV) and Th(IV) with 1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedione (FOD) as -diketone and a variety of neutral oxodonors were synthesized and characterized by visible spectral, proton magnetic resonance as well as thermogravimetric studies. Adducts with dimethylformamide (DMF) were found to be most volatile, whereas with trioctylphosphine oxide (TOPO) were quite susceptible towards decomposition.

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Abstract  

Present work summairzes a method for the estimation of uranium in the presence of plutonium involving the reduction of uranium to U/IV/ and plutonium to Pu/III/ by Zn/Hg/ followed by the selective oxidation of Pu/III/to Pu/IV/with HNO3 catalyzed by molybdate in the presence of large sulphate concenration [5M H2SO4+1.5M /NH4/2SO4]. The oxidation of U/IV/ by K2Cr2O7 is then carried out in the presence of excess of Fe/III/ and Al/NO3/3 to a sharp potentiometric end point. R.S.D. obtained for 20 determinations of uranium /3–6 mg/ was 0.3% in the presence of 0.35 mg of plutonium. Larger quantity for plutonium was found to interfere.

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Abstract  

Ni/III/ has been employed as an oxidant for the quantitative oxidation of plutonium to its hexavalent state and this makes possible to determine plutonium concentrations potentiometrically by the Fe/II/-dichromate redox titration method. The unreacted oxidant is completely reduced by sulphamic acid prior to the determination of plutonium.

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Abstract  

The separation characteristics of hydrogen-tritium mixtures by gas chromatography at 77 K have been studied using molecular sieve 4A, coated with 5 wt% vanadium in the form of V2O4, as supporting material. The performance of the column was found to be better than that observed on the conventional coated and uncoated molecular sieves in terms of reduced retention times, resolution, nature of the peak and added thermal stability of the stationary phase.

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Abstract  

Isotope exchange behaviour of bis/diethyldithiocarbamate/mercury/II/ complex has been studied at 25°C and 45°C varying the concentrations of both metal ion and the complex. The results show that the complex is kinetically labile. Temperature has a significant effect on the rate of the reaction. Increase in concentration increases the reaction rate.

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Abstract  

The potentiometric determination of uranium is widely carried out in phosphoric acid medium to suppress the interferences of plutonium by complexation. Owing to the complexity of the recycling plutonium from the phosphate based waste involving manifold stages of separation, a method has been proposed in the present paper which does not use phosphoric acid. Uranium and plutonium are reduced to U/IV/ and Pu/III/ in 1M H2SO4 by Ti/III/, and NaNO2 is chosen to selectively oxidize Pu/III/ and the excess of Ti/III/. The unreacted NaNO2 is destroyed by sulphamic acid and excess Fe/III/ is added following dilution. The equivalent amount of Fe/II/ thus liberated is titrated against standard K2Cr2O7. R.S.D. obtained for the determination of uranium /1–2 mg/ is 0.3% with plutonium being present upto 4.0 mg.

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The high temperature superconducting compound YBa2Cu3O72212;δ (Y-123) is synthesised by sol-gel process using various precursors viz., acetate, acetate-citrate, nitrate-citrate and acrylamide. The phase purity of the final product depends on the homogeneity of the gels which intern depends on the bonding of the metal ions in the gels. The samples prepared by acrylamide and nitrate-citrate gel routes yielded phase pure Y-123 compound with better superconducting properties. The mechanism of formation of Y-123 in all these four gel routes is established by characterising the gels and intermediate phases using TG, DTA and XRD techniques. Kinetic analysis is carried out on the mass loss data using the method proposed by Phadni's and Deshpande. Avrami-Erofeev nuclei growth in case of acrylamide, diffusion controlled process in nitrate-citrate and phase boundary reaction mechanisms in case of acetate-citrate gels are found to be responsible for the formation of Y-123 phase.

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