Studies in bivalent chromium salts

Summary The accuracy of the proposed visual technique of standardising chromous sulphate solution has been compared with the potentiometric method and it has been shown that there lies a fair agreement between the titre values obtained visually as well as potentiometrically. Both calomel and glass electrodes together with platinum electrode have been employed with equal facility in the present series of investigations. The use of glass electrode in place of saturated calomel electrode makes the measurements even more simpler and prevents the least possible contamination of chromous solution with mercurous salt. The simplicity as well as accuracy of the visual technique can thus be expected to increase the utility and applicability of chromous salts to a very great extent.

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Zusammenfassung Die Einstellung von Chrom(II)-lösungen wurde visuell und potentiometrisch durchgeführt. Es wird gezeigt, daß beide Methoden gut übereinstimmende Ergebnisse liefern. Sowohl die Kalomel- als auch die Glaselektrode wurden zusammen mit der Platinelektrode mit gleich, gutem Erfolg verwendet. Die Anwendung einer Glaselektrode an Stelle der ges. Kalomelelektrode macht jedoch die Messungen noch einfacher und verhindert auch die geringste Verunreinigung der Chrom(II)-lösung mit Quecksilbersalz. Die Einfachheit und Genauigkeit der visuellen Methode kann dazu beitragen, die Anwendbarkeit der Chrom(II)-salze erheblich zu erweitern.

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Part. VIII: Tandon, J. P.: Z. analyt. Chem. 167, 184 (1959).     

Studies in bivalent chromium salts

Summary It has been demonstrated that colourless leuco-methylene blue is oxidised back quantitatively to the original dyestuff, by various oxidising agents. The methods for the estimation of potassium chromate, potassium persulphate, potassium periodate, ferric iron, sodium and hydrogen perioxide have been worked out by estimating the oxidised leuco-dye with chromous sulphate.The authors express their gratitude to the college authorities for providing the necessary facilities for work.Part IV: cf. Z. analyt. Chem. 159, 422 (1958).     

Studies in bivalent chromium salts

Summary A comparative study of reduction of triphenylmethane (rhodamine, rosaniline, methyl violet and aniline blue), indigoid (isatine) and quinoneimine (safranine) dyes with chromous sulphate and titanous chloride has been made and it has been shown that all these dye-stuffs can be successfully titrated against chromous sulphate. It thus provides an alternative method for the estimation of the dyes belonging to the various groups.

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Zusammenfassung Es wurde eine vergleichende Untersuchung über die Reduktion von Triphenylmethan-, Indigoid- und Chinoniminfarbstoffen mit Chrom(II)sulfat sowie Titan(III)-chlorid vorgenommen. Zur volumetrischen Bestimmung wird die Titration mit Chrom(II)-sulfatlösung empfohlen. Folgende Farbstoffe der einzelnen Gruppen wurden untersucht: Rhodamin, Rosanilin, Methylviolett, Anilinblau, Isatin, Safranin.

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Part IX: Tandon, J. P., and R. C. Mehrotra: Z. analyt. Chem. 187, 410 (1962).

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Thanks are due to Dr. R. C. Mehrotra, Professor and Head of the Department of Chemistry, for his keen interest in the work.     

Studies in bivalent chromium salts

Summary The above estimations show that stannous chloride and uranyl acetate can be estimated with the help of chromous sulphate. In the case of tin, excess of ferric iron is added and its excess found by titration with chromous sulphate, using neutral red or phenosafranine as indicator. In the case of uranyl acetate chromous salt titration, the above two indicators work satisfactorily in the absence of excess of sulphuric acid, whereas methyl red and p-ethoxycrysodine give good end points even in the presence of excess acid. In the alternative procedure for estimation of uranium, chromous sulphate serves the purpose of a Jone's reductor.Ammonium metavanadate solution can be titrated directly against chromous sulphate. N-phenylanthranilic acid, diphenylamine, diphenylbenzidine and diphenylamine sulphonic acid serve satisfactorily as internal indicators for the VO_3– to VO²⁺ change. It has been shown that ferric and cupric salts do not interfere in the above titrations. Mixtures of vanadate and dichromate or vanadate and ceric sulphate can also be titrated in the same manner using the same indicators.Part VI: cf. Z. analyt. Chem. 162, 33 (1958).     

Studies in bivalent chromium salts

Summary It has been shown that chromous solution can be standardised with the help of potassium dichromate, sulphatocerate, potassium iodate, bromate and periodate solutions. N-phenylanthranilic acid, ferroin and diphenylbenzidine serve as reversible indicators for the titrations of potassium dichromate and ceric sulphate against chromous solution.The authors are indebted to Dr. R. N. Singh, Professor of Chemistry, B. R. College, Agra, for his kind encouragement and for providing laboratory facilities.Part II: See Z. anal. Chem. 158, 189 (1957).     

Studies in bivalent chromium salts

Summary As shown in the above investigations, chromous sulphate can be used for the quantitative reduction of compounds containing nitro, nitroso, quinoid, and azo groups. In the case of the first three, the estimations can be carried out by either of the two methods, direct titration by using neutral red, phenosafranine orp-ethoxychrysoidine as internal indicators, or by adding excess of chromous sulphate and titrating the excess with ferric solution, using thiocyanate as indicator. The comparative study of reduction of azodyes shows that the dyes can be estimated quantitatively with chromous sulphate as well. It is also possible to estimate the carbohydrates, since the unused copper sulphate can be directly titrated against chromous sulphate in presence of neutral red or phenosafranine as indicator. The results are fairly satisfactory and within experimental error (± 0.9°/0).The author is highly indebted to Dr. R. C. Mehrotra, Professor of Chemistry, Gorakhpur University, for his helpful suggestions and keen interest in the work.Part VII: See. Z. analyt. Chem. 164, 314 (1958).     

Studies in bivalent chromium salts

Summary It has been shown in these investigations that the titrations of methylene blue, indigo, crystal violet, eosin, malachite green, magenta and orange G can be carried out successfully with chromous sulphate solution. Comparative results with titanous chloride and chromous sulphate indicate a fair degree of agreement. However, the reduction is found to be more facile with chromous sulphate.Part I: See Z. analyt. Chem. 158, 20 (1957).The authors' thanks are due to Dr. R. N. Singh, Professor of Chemistry, B. R. College, Agra, for providing laboratory facility and encouragement.     

Studies in bivalent chromium salts

Summary As shown above, the estimations of potassium persulphate, hydrogen peroxide and dissolved oxygen in water, can be carried out with the help of chromous sulphate, by either of the two methods: (i) adding excess of chromous sulphate and titrating the excess with ferric solution using thiocyanate as indicator; (ii) adding to an excess of ferrous solution and titrating the ferric iron produced with chromous sulphate, using neutral red or thiocyanate as indicator. The results obtained by the above two methods are fairly satisfactory.Part III: cf. Z. analyt. Chem. 159, 5 (1958).The authors' thanks are due to the College authorities for providing the necessary facilities for work.     

The kinetics and mechanism of the reduction of short-bond compounds in aqueous solutions of salts containing bivalent chromium

The kinetics of the reduction of acetylene and fumaric acid in aqueous and aqueous alcoholic solutions by chromous chloride have been investigated.Reversible formation of a complex of Cr²⁺ with acetylene has been observed, and this is apparently an intermediate product in the production of acetylene. The rate of the reduction reaction in both cases is proportional to the square of the chromous ion concentration, and to the concentration of the unsaturated compound. In the reduction of acetylene, the rate of the reaction is proportional to the concentration of the hydrogen ion; in the reduction of fumaric acid the action is somewhat retarded when hydrogen ion concentration is increased.A mechanism for the reaction is proposed, in which in the rate-determining stage hydrogen is transferred to the short bond in the complex made up of two ions of chromium and the unsaturated compounds.     

Interaction of diphenylacetylene with chromium salts

The reaction of diphenylacetylene with chromium atoms results in the formation of bisarenechromium π-complexes containing diphenylacetylene and its cyclotrimer as ligands, viz., bis(η⁶-diphenylacetylene)chromium, (η⁶-diphenylacetylene)(η⁶-hexaphenylbenzene)chromium and bis(η⁶-hexaphenylbenzene)chromium. The other reaction products were found to be uncomplexed hexaphenylbenzene and 1,2,3,4-tetraphenylbutadiene-1,3.     

Complexes of some bivalent metal salts with benzo(f)quinoline

Summary Coordination compounds have been prepared from benzo(f)quinoline (BNQ) and some bivalent metal salts,viz., Cu(BNQ)Cl₂, Cu(BNQ)₂Br₂, Cu(BNQ)SO₄ · H₂O, Co(BNQ)₂(NCS)₂, Ni(BNQ)₂(SCN)₂, Cu(BNQ)(SCN)₂, Zn(BNQ)₂(NCS)₂, Cd(BNQ)₂(SCN)₂ and Hg(BNQ)(SCN)₂. The products have been characterized by magnetic susceptibility, electronic and i.r. spectral measurements down to 200 cm^–1. Tentative stereochemistries for the complexes isolated in the solid state are discussed.     

Studies of chromium stearate

Evidence is presented which throws doubt on the preparation of chromium III tri-stearate by aqueous metathetic reaction.     

Studies of chromium cages and wheels

Studies of two distinct classes of chromium(III) cage complexes are discussed. The first are compact oxo- and carboxylate cages, made by heating precursors to high temperature under a flow of nitrogen. One of these cages, [Cr₁₂O₉(OH)₃(O₂CCMe₃)₁₅], has an S = 6 spin ground state which proves a very interesting subject for study by EPR and MCD spectroscopy. Use of other carboxylates leads to other octa- and dodeca-nuclear complexes. The second class of compounds are homo- and hetero-metallic wheels and chains bridged by fluoride and carboxylates. These include the first heterometallic anti-ferromagnetically coupled ring systems and are being widely studied in areas as diverse as magnetic cooling and quantum information processing. The mechanism by which these unusual cyclic and acyclic structures form is discussed.     

Studies on 2-acetylpyridineisonicotinoyl hydrazone complexes of some bivalent 3d-metal ions

2-Acetylpyridineisonicotinoyl hydrazone (Hapinh) complexes of OV(II), Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) having 1:1 metal-ligand stoichiometry have been prepared and characterised by elemental analyses, molar conductance, magnetic susceptibility, electronic, infrared, ESR and NMR (¹H and¹³C) studies. Octahedral/distorted octahedral geometry has been assigned for the OV(II), Mn(II), Ni(II), Cu(II) and Zn(II) complexes while tetrahedral and trigonal bipyramidal configurations have been suggested for the Co (II) adduct and deprotonated complexes respectively. IR and NMR spectral studies suggest a tridentate behaviour of Hapinh and apinh⁻ species in the adducts and deprotonated complexes respectively.     

Schiff碱二价金属离子配合物的合成及抗菌性

氨基酸、肽、蛋白质、酶等生物大分子中半光氨酸残基上的硫原子与一些过渡金属离子形成的配合物具有特殊的生物活性,因此配体和配合物的研究一直受到人们的重视[1,2]。我们设计并合成出的乙酰基硫代甲酰取代苯胺缩氨基脲Schiff碱具有与这些生物大分子相同的配位原子,可以作为研