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1.
Summary A new volumetric method for cerium determination based on the quantitative reduction of Ce(SO4)2 by excess potassium thiocyanate and titration of the excess with standard KMnO4 to the ICl end point has been described.Sincere thanks of the authors are due to Professor S. S. Joshi for facilities and kind interest in the work. The award of a U. P. Scientific Research Committee Scholarship to one of us (M.K.J.) is also gratefully acknowledged.  相似文献   

2.
Summary Determination of cerium(IV), depending upon its reduction to cerium-(III) by KI and titration of the liberated iodine with standard arsenious oxide solution in a suitably adjusted pH range, is described.Sincere thanks of the author are due to Professor S. S. Joshi for research facilities.  相似文献   

3.
Summary Bismuth is shown to be precipitated quantitatively as bismuth selenite by boiling an almost neutral solution of bismuth nitrate and excess selenious acid. The excess H2SeO3 is determined iodometrically by standard thiosulphate or arsenious oxide solution. Alternatively, the precipitated selenite may be dried at 105–110° C and weighed as Bi2(SeO3)3.Sincere thanks of the authors are due to Prof. S. S. Joshi for research facilities and to Dr. G. S. Deshmukh for keen interest in the work.  相似文献   

4.
Spectrophotometric kinetic technique has been used to investigate the effect of cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulfate (SDS) surfactants on the redox reaction of cerium(IV)+l-sorbose in aqueous sulfuric acid media. The anionic SDS has no effect, whereas the reaction rate increases in the presence of cationic CTAB, which is due to favorable conditions provide by the cationic micelles. The reaction rate decreases with [H2SO4], and no acid-dependent path has been observed. At constant [H2SO4], the rate of the reaction is dependent on the first powers of the l-sorbose and cerium(IV) concentrations. The CTAB-assisted reaction is retarded by addition of electrolytes (Na2SO4, NaNO3, and NaCl), which is attributed to the competition between electrolyte anions and cerium(IV)-sulfato species. Bromide ion (of CTAB or externally added in the form of NaBr) is not oxidized by the cerium(IV) (as a main or side reaction).  相似文献   

5.
Summary The quantitative oxidation of thiocyanate by ceric sulphate has been studied and the method utilised for the determination of small quantities of cerium by back titrating the excess (unreacted) KSCN against standard mercuric nitrate with diphenylcarbazone as the internal indicator. Accurate results are obtained under the specified experimental conditions and the procedure is more simple and direct than that adopted during earlier studies of the above redox reaction.Grateful thanks of the author are due to Professor S. S. Joshi for facilities during the work and to the National Institute of Sciences of India for award of a Research Fellowship.  相似文献   

6.
Kinetics of Br anion oxidation by cerium(IV) species in aqueous H2SO4 solutions have been reexamined. The rate of reaction was determined spectrophotometrically based on a factor analysis of the absorbance – time data collected in the wavelength range 318–390 nm – the region characteristic for the cerium(IV) sulphato complexes. The data fit very well to a pseudo-first order dependence under a large molar excess of the reductant. The rate law of the form –d[CeIV]/dt = k[CeIV][Br]2 has been obtained at constant H2SO4 concentration and ionic strength I = 2 m. The pseudo-first order rate constant decreases with an [H2SO4] increase from 0.1 to ca. 0.4 m range, then increases for higher [H2SO4]. The apparent activation parameters have been calculated from the third order rate constants k for different [H2SO4].  相似文献   

7.
Summary Conditions are described for the quantitative precipitation of bismuthyl dichromate, (BiO)2Cr2O7, and the suitability of this reaction for the gravimetric estimation of bismuth is shown. The use of arsenious oxide as a primary standard for the iodometric titration of excess chromate is emphasised.Sincere thanks of the authors are due to Prof. S. S. Joshi for research facilities and to Dr. G. S. Deshmukh for keen interest in the work.  相似文献   

8.
Summary Conductometric titrations of thorium chloride against oxalic acid, ammonium oxalate and silver nitrate have been carried out at high dilutions (0.001, 0.0005 and 0.00033 M) of the chloride. Oxalic acid is found to be a suitable titrant for rapid estimation of thorium, the minimum error being +0.5%. The other titrants do not give good results. The titrations with ammonium oxalate indicate the step-wise ionisation of ThCl4 into ThCl2 2+, ThCl3+ and Th4+. For mixtures of thorium chloride and cerous chloride, only the equivalence point corresponding to complete precipitation of both thorium and cerium is indicated.The authors express their sincere thanks to Prof. S. S.Joshi for his keen interest in this work and to Dr. G. S.Deshmukh for his advice and help in so many ways during the progress of these studies.  相似文献   

9.
The influence of surfactants (anionic and cationic) on the reactivity of the redox couple cerium(IV) and D-glucose was examined spectrophotometerically. Various kinetic parameters have been determined in the absence and presence of surfactants. The kinetics were followed by monitoring the disappearance of the absorbance of cerium(IV) at 385 nm. The reaction obeyed first-order kinetics with respect to [D-glucose] in both media. No effect of anionic micelles of sodium dodecyl sulfate (SDS) was observed due to electrostatic repulsion between the negative head group of SDS and reactive species of cerium(IV) (Ce(SO4) 3 2− ). A twofold increase in the oxidation rate was observed in the presence of cationic micelles of cetyltrimethylammonium bromide (CTAB). The observed catalytic role has been analyzed in terms of the Menger–Portnoy model. The effects of various inorganic salts (Na2SO4, NaNO3 and NaCl) were also studied in micellar media.  相似文献   

10.
Summary A volumetric method of estimating selenium, depending upon the reduction of selenious acid by excess hydrazine sulphate solution and titration of the excess against KIO3 to the iodine monochloride end point, has been described. Determination of tellurium on these lines is suggested.The author is indebted to Professor S. S.Joshi for facilities and kind interest in the work. The award of a Scientific Man Power Committee Research Fellowship is also gratefully acknowledged.  相似文献   

11.
Summary Quadrivalent selenium can be determined with fair accuracy by mixing with an excess of KMnO4 in the presence of 25–75 ml of 2% NaF solution and 4–7 ml of 9 N sulfuric acid. After leaving the reaction mixture for 10–30 minutes the excess KMnO4 is estimated by one of the following procedures: A) Titration of the excess KMnO4 with monovalent mercury, B) Adding an excess of Hg2 2+ solution to react with the excess KMnO4 followed by titrating the excess mercurous with KMnO4 solution.Part I: Issa, I. M., and M. Hamdy, Z. analyt. Chem. 172, 94 (1980).  相似文献   

12.
Summary The titration of ferrous iron in presence of fluoride ions in acid medium gives fleeting end points and erroneous results. A method is deviced to overcome this difficulty by oxidising the ferrous with an excess of KMnO4 in alkaline medium. After mixing the reactants the excess of KMnO4 is reduced by an excess of Hg2 2+ ions in presence of H2SO4 and fluoride. The remaining mercurous is then titrated with standard KMnO4 solution.Part III: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 174, 418 (1960).  相似文献   

13.
    
Summary The oxidation of hydroxylamine by alkaline ferricyanide has been studied. It is observed that in presence of sodium hydroxide the molar ratio of NH2OH to K3Fe(CN)6 varies between 11.3 to 11.6. Quantitative oxidation to N2 is therefore carried out in weakly alkaline medium using borax-boric acid buffer. Hydroxylamine is estimated by titrating the ferrocyanide formed with standard ceric sulphate. Accurate and reproducible results are obtained if too large an excess of ferricyanide is avoided. Application of the present procedure to the determination of oximes and their metal complexes is suggested.Grateful thanks of the author are due to Prof. S. S. Joshi for facilities and encouragement and to Dr. G. S. Deshmukh for kind interest in the work.  相似文献   

14.
The oxidative degradation of d-xylose by cerium(IV) has been found to be slow in acidic aqueous solution with the evidence of autocatalysis. The reaction is accelerated in the cetyltrimethylammonium bromide (CTAB) micellar medium but sodium dodecyl sulfate (an anionic surfactant) has no effect. The pseudo first-order rate constants have been determined at different [reductant], [oxidant], [H2SO4], temperature, and [CTAB]. The reaction rate increased with increasing [d-xylose] and decreased with increase in [H2SO4]. The CTAB-micelle-catalyzed kinetic results can be interpreted by the pseudophase model. The kinetic parameters such as association constant (K s), micellar medium rate constant (k m), and activation parameters (E a, ΔH # and ΔS #) are evaluated and the reaction mechanism is proposed. The reaction rate is inhibited by electrolytes and the results provide an evidence for the exclusion of the reactive species from the reaction site.  相似文献   

15.
Summary Trivalent chromium and quadrivalent vanadium can be determined with fair accuracy by a method consisting in mixing either with an excess of KMnO4 in the presence of 0.3 to 1.8 M alkali hydroxide. After leaving the mixture for 5 min, the solution is acidified with sulphuric acid and mixed with 50 to 75 ml of 2% NaF solution. An excess of monovalent mercury Hg2 2+ solution is then added, the solution heated to 40° C and then titrated with KMnO4 solution in the presence of Cu2+ ions to conceal the pink manganic fluoride colour.Part II: Issa, I. M., and M. Hamdy: Z. analyt. Chem. 172, 162 (1960).  相似文献   

16.
The oxidation of methylene blue (MB+) by cerium(IV) was studied in 0.1–5 M H2SO4. The reaction proceeds via MB radical (MB2+•) formed by one electron transfer to the oxidant. The radical is observed spectrophotometrically by a very intense absorbance at λmax = 526 nm and by the e.p.r signal at g = 2.000. The kinetics of the fast radical formation are two orders of magnitude slower than its decomposition, which were examined using a stopped-flow method at 298 K under pseudo-first order conditions. The rate laws for the both steps were determined and a likely mechanism reported.  相似文献   

17.
The trifunctional ligand, 2,6-bis(diphenylphosphorylmethyl)-4-methylphenol (L 2), forms complexes with cerium(III) nitrate having a ligand to metal ratio of 1: 1, 2: 1, and 3: 1. The structures of these complexes in the solid state and in solution were studied by X-ray diffraction, IR and NMR (1H and 31P) spectroscopy, and conformational analysis (molecular mechanics). The 2: 1 complexes of L 2 with lanthanum(III) and neodymium(III) nitrates were synthesized and characterized. In all complexes, the neutral ligand is coordinated through both phosphoryl oxygen atoms. The hydroxy oxygen atom is coordinated only in some complexes, and the hydrogen atom of the hydroxy group is involved in hydrogen bonding. The compositions and structures of the resulting complexes depend on the method of synthesis and the nature of solvent. The ligand was found to undergo easy inner-sphere oxidation. The structure of one of the transformation products was established by X-ray diffraction. Unlike the coordinated ligand, the free ligand is very stable to oxidation. Dedicated to Corresponding Member of the Russian Academy of Sciences T. A. Mastryukova. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2440–2454, November, 2005.  相似文献   

18.
Summary Results are given for a two stage oxidation in the ascorbic acid-KIO3 reaction under controlled conditions of acidity. The first step corresponds to the Landolt reaction and the second end point is obtained by the classical Andrews method. The reproducibility and accuracy of the results calculated on the basis of the two successive end points constitute an interesting new feature of this redox reaction involving the use of KIO3 as a primary standard for the determination of ascorbic acid.Our sincere thanks are due to Professor S. S. Joshi for kind interest in the work and to the National Institute of Sciences of India for award of a Research Fellowship to one of us (G. S. D.).  相似文献   

19.
Summary The reaction between Tl+ solutions and manganate is sluggish. In the titration of Tl+ with manganate solution the end points are always attained earlier than the theoretical. When the reaction is accelerated by NaCl and heating to 45–50° C the end points were found to be concordant with the theoretical values. Titration of manganate with Tl+ solutions gives accurate results in presence of telluric acid but not in its absence. It is also possible to determine Tl+ by oxidation with an excess of K2MnO4 using arsenite as a back titrant for excess oxidant.Part III: Issa, I. M., and M. G. E. Allam: Z. analyt. Chem. 175, 103 (1960).  相似文献   

20.
The cerium content and the film thickness of cerium-activated alkaline earth metal sulfide films were determined simultaneously. The cerium determination was calibrated by using standard solutions on filter paper. Film thickness was determined by comparing the S Kα intensities with those in zinc sulfide standards. The detection limit for cerium was estimated to be 0.1 μg cm?2.  相似文献   

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