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41.
V. K. Manchanda G. A. Rama Rao P. R. Natarajan 《Fresenius' Journal of Analytical Chemistry》1982,312(7):611-612
Summary A method for the determination of U in the presence of Pu based on the reduction of U to U(IV) and Pu to Pu(III) by zinc amalgam followed by oxidimetry of U(IV) has been developed. Fe(III) perchlorate was chosen as the most suitable titrant for the selective oxidation of U(IV) as conventional oxidising titrants fail in the presence of Pu(III). The potentiometric titration of U(IV) with Fe(III) is known to be slow. This problem, however, has been overcome by selecting a suitable buffer medium and complexing agent to alter the potentials of the Fe(III)/Fe(II) and U(VI)/U(IV) systems in the favourable direction. Results of the titration of U(IV) with Fe(III) at pH 2 in the presence of ferrozine as complexing agent for Fe(II) are summarized. R.S.D. obtained for twenty determinations of 3–5 mg of U was 0.3 % in the presence of 1–4 mg of Pu.
Volumetrische Bestimmung von Uran in einem U/Pu-Gemisch mit Hilfe von Fe(III)
Zusammenfassung Das Verfahren beruht auf der Reduktion von U zu U(IV) und Pu zu Pu(III) mit Hilfe von Zinkamalgam und anschließender Titration mit Fe(III)-perchlorat. Dieses Reagens hat sich für die selektive Oxidation des U(IV) am besten bewährt, da andere Oxidationsmittel in Gegenwart von Pu(III) versagen. Die Endpunktsindikation erfolgt potentiometrisch, wobei die an sich langsame Einstellung des Endpunktes dadurch beschleunigt wird, daß durch Zusatz eines geeigneten Puffers und eines Komplexierungsmittels (Ferrozin) für Fe(II) die Redoxpotentiale von Fe(III)/Fe(II) und U(VI)/U(IV) entsprechend verschoben werden. Die relative Standardabweichung für die Bestimmung von 3–5 mg U in Gegenwart von 1–4 mg Pu liegt bei 0,3%.相似文献
42.
The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we
use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained
from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized
neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star
masses is minimal. 相似文献
43.
N. Gopinath G. A. Rama Rao V. K. Manchanda P. R. Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》1985,96(3):273-280
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. 相似文献
44.
V. K. Manchanda P. K. Mohapatra 《Journal of inclusion phenomena and macrocyclic chemistry》1993,15(2):121-130
Complexation of Am(III) with a tris-bipyridine cryptand (L) has been carried out in a nonaqueous medium (CH3CN–CHCl3). Subsequently the complexation behaviour was investigated using the reverse extraction tracer technique with dinonyl naphthalenesulphonic acid (HD) in toluene as the organic phase and varying concentration of HCl (upto 2M) as the aqueous phase. Equilibrium is attained in the two-phase system at a rate dependent on the hydrogen ion concentration in the aqueous phase. Whereas it takes only a few minutes to attain the equilibrium state at pH 6.0, a phase contact period of 50 days was insufficient if the acidity is greater than 0.4M, presumably due to the slow dissociation of the cryptate formed. The large enhancement in the distribution ratio value in the synergistic system with 1M HCl as the aqueous phase under non-equilibrium conditions is employed for the analytical separation of Am(III) from Eu(III). 相似文献
45.
P. C. Kalsi Pramilla D. Sawant A. Ramaswami V. K. Manchanda 《Journal of Radioanalytical and Nuclear Chemistry》2007,273(2):473-477
Garware Polyester Film, an indigenously available material has been evaluated systematically as a nuclear track detector for
the detection of fission fragments. The relative fission track detection efficiency of this film was found to be (86.0±4.0)%.
The bulk etch rate, determined by the gravimetric method, was found to be 0.75±0.05 μm/h. The track etch rate was determined
as 15.0±1.5 μm/h. This detector was employed for the estimation of uranium in seawater samples and the results obtained were
compared with the results obtained by using the commonly used Lexan detector. Uranium fractions after chemical separation
from seawater samples were also analyzed by alpha-spectrometry and neutron activation analysis techniques and the results
were compared with that obtained by the fission track method. Fission track method has the advantage, as it does not require
any chemical separation. The indigenously available polyester film (polyethylene terphthalate) appears to be a good substitute
of Lexan as nuclear track detector. 相似文献
46.
V. K. Manchanda G. A. Rama Rao D. R. Hanwate 《Journal of Radioanalytical and Nuclear Chemistry》1983,76(1):63-71
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. 相似文献
47.
2-(5-Bromo-2-pyridylazo)-5-(diethylamino) phenol (Br-PADAP) forms a 1:1 complex with the uranyl ion in the presence of sulphosalicylic acid, which acts as stabilizer for this complex in the triethanol amine/perchloric acid buffer system. A change in the stoichiometry of the complex was seen at pH<5. Kinetic measurements were carried out using stopped-flow spectrophotometer in the presence of an excess concentration of U(VI) in the pH range 6.5 to 8. The dependence of the pseudo-first-order rate constant, k(obs), on the concentrations of U(VI), ligand and hydrogen ion showed that Br-PADAP reacts with UO2(OH)+ to form an intermediate species (equilibrium constant = 1.28×104mol.dm−3) that then rearranges (rate constant = 5.6×10−2s−1) to form the product species. UO2(OH)+ is present in equilibrium with the unreactive species UO2(OH)2, as well as with the unreactive sulfosalicylic acid complex. 相似文献
48.
V. K. Manchanda G. A. Rama Rao W. D. Lloyd 《Journal of Radioanalytical and Nuclear Chemistry》1990,139(2):223-229
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. 相似文献
49.
G. A. Rama Rao V. K. Manchanda P. R. Natarajan 《Journal of Radioanalytical and Nuclear Chemistry》1985,94(2):95-100
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. 相似文献
50.
T. L. Prasad P. C. Kalsi R. Acharya V. K. Manchanda P. K. Tewari 《Journal of Radioanalytical and Nuclear Chemistry》2012,294(3):465-470
Nuclear analytical techniques namely fission track technique using solid state nuclear track detector (SSNTD) and instrumental neutron activation analysis (INAA) have been standardized and applied for quantification of low uranium concentrations in liquid samples such as feed, elute and brine and solid sorbent samples respectively. The quantification of uranium is required for its recovery study from seawater, which is one of the potential sources of uranium. The uranium concentration of a liquid sample obtained by SSNTD method was compared with the other well established conventional techniques like ICP-MS, ICP-AES, adsorptive stripping voltametry and alpha spectrometry. INAA was applied for uranium concentration determination in the radiation grafted polyamidoxime sorbent samples. 相似文献