Preparation and thermal decomposition of some oxomolybdenum(VI) oxalates

Anionic oxomolybdenum(VI) oxalates having the general formula A₂[Mo₂O₆(C₂O₄)], where A = K⁺ and NH⁺₄, are prepared and characterized by chemical analysis and IR spectra, and their thermal decomposition studied using TG and DTA techniques. Both the compounds are anhydrous and the decomposition of oxalate takes place in a single step. The ammonium compound decomposes between 255 and 320°C to give MoO₃ as the end product, while the potassium compound decomposes between 300 and 380°C to give K₂Mo₂O₇ as the end product. Both the products were characterized by chemical analysis, IR and X-ray studies. The X-ray diffraction patterns of the two oxalato complexes confirm that they are crystalline compounds.     

Synthesis and characterisation of heterobimetallic <Emphasis Type="Italic">N</Emphasis>-(hydroxyethyl)-salicylaldiminate–isopropoxide complexes of oxovanadium(V)

Soluble heterobimetallic-N-(hydroxyethyl) salicylaldiminate-alkoxide derivatives of the types [VO(L)₂{M(OPrⁱ)_n−1}] [M=Al (2) (n = 3); Ti (3), Zr (4) (n = 4); Nb (5), Ta (6) (n = 5)], [where L represents the dianionic N-(hydroxyethyl) salicylaldiminate group bonded to vanadium in a tridentate fashion involving both the oxygen atoms and azomethine nitrogen], have been prepared by the reactions of insoluble [VO(L)(LH)] (1) with different metal alkoxides in a 1:1 molar ratio in benzene. A monomeric heterobinuclear complex of the type [VO(η³-L)(μ-OPrⁱ)₂Al(η³-L)] (7) has been prepared by the equimolar reaction of [VO(η³-L)(μ-OPrⁱ)]₂ with [Al(η₃-L) (μ-OPrⁱ)]₂ in benzene. All these complexes have been characterised by elemental analyses, molecular weight measurements, and by spectroscopic (l.r., ¹H-, ²⁷Al- and ⁵¹V-n.m.r.) studies. The monomeric nature of (1) and (2) has been supported by their FAB-mass spectral studies.     

Ultrasonic measurements and other allied parameters of yttrium soaps in mixed organic solvents

The ultrasonic measurements of yttrium soaps were made in a mixture of 70% benzene and 30% dimethylsulfoxide (v/v) to determine the critical micelle concentration, soap-solvent interaction and various acoustic and thermodynamic parameters. The values of the CMC decrease with increasing chainlength of fatty acid constituent of the soap molecule and are in agreement with the values obtained from other micellar properties. The various acoustic parameters (intermolecular free-length, adiabatic compressibility, apparent molar compressibility, specific acoustic impedance, apparent molar volume, molar sound velocity, solvation number, available volume and relative association) for yttrium soaps (myristate, palmitate, stearate and oleate) have been evaluated by ultrasonic velocity measurements.

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Ultraschallmessungen und damit verknüpfte Parameter von Yttrium-Seifen in gemischten organischen Lösungsmitteln

Zusammenfassung Es wurden Ultraschallmessungen von Yttrium-Seifen in einer Mischung 70% Benzol und 30% Dimethylsulfoxid (v/v) durchgeführt, um die kritische Micellenkonzentration, Seifen-Solvens-Wechselwirkung und verschiedene akustische und thermodynamische Parameter zu bestimmen. Die CMC-Werte fallen mit steigender Kettenlänge der Fettsäurekomponente des Seifenmoleküls und sind damit in Übereinstimmung mit den aus anderen micellaren Eigenschaften bestimmten Werten. Verschiedene akustische Parameter (intermolekulare freie Länge, adiabatische Kompressibilität, effektive molare Kompressibilität, spezifische akkustische Impedanz, effektives molares Volumen, molare Schallgeschwindigkeit, Solvatationszahl, verfügbares Volumen und relative Assoziation) der Yttrium-Seifen (Myristat, Palmitat, Stearat und Oleat) wurden aus den Ultraschallmessungen ermittelt.

     

Ultrasonic and viscosimetric studies of samarium laurate in benzene-dimethylsulfoxide mixtures

Summary Ultrasonic and viscosity measurements of samarium laurate in benzene-DMSO mixtures of different compositions (7:3 and 1:1 V/V) have been used to determine the critical micelle concentration (CMC), soap-solvent interaction, and various acoustic parameters of the system. The values of critical micelle concentration increase with increasing amount ofDMSO in the solvent mixtures. The viscosity results have been explained on the basis of equations proposed byEinstein,Vand. Moulik, andJones-Dole. The values of CMC for samarium laurate obtained from the viscosity measurements are in agreement with the results obtained from ultrasonic measurements. The results show that the soap molecules do not aggregate appreciably below CMC; there is a marked change in the aggregation behaviour at CMC.

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Ultraschall- und Viskositätsmessungen an Samariumlaurat in Benzol-DMSO-Mischungen

Zusammenfassung Mit Hilfe von Ultraschall- und Viskositätsmessungen an Samariumlaurat in Benzol-DMSO — Mischungen verschiedener Zusammensetzung (7:3 und 1:1 v/v) wurden die kritische Micellenkonzentration (CMC), Seife-Lösungsmittel-Wechselwirkungen und verschiedene akustische Parameter des Systems bestimmt. Die Werte für die kritische Micellenkonzentration steigen mit wachsendem Anteil vonDMSO im Lösungsmittelgemisch. Die Érgebnisse der Viskositätsmessungen werden auf der Basis der Gleichungen vonEinstein,Vand,Moulik undJones-Dole erklärt. Die CMC-Werte für Samariumlaurat aus Viskositäts- und Ultraschallmessungen stimmen überein. Die Ergebnisse zeigen, daß die Seifenmoleküle bei Konzentrationen unter CMC nicht stark aggregieren; bei Erreichen des CMC-Werts tritt eine ausgeprägte Änderung im Aggregationsverhalten ein.

     

Design of molecular precursors

Successful synthesis of a variety of volatile and alcohol soluble heterometal alkoxides (with 2, 3, 4, or more different metals in the same monomeric molecule) with chelating ligands, e.g., {A1(OPrⁱ)₄}^–, {Zr₂(OPrⁱ)₉}^–, and {Nb(OPrⁱ)₆}^– around a central metal atom, which may also be bound with simpler ligands also like (OR)^–, (acac)^–, (acetate)^– has not only added a new dimension to the stable multi-metal coordination systems, but has opened up the possibilities of designing a molecular precursor corresponding to the targeted material. It has been shown that the final material obtained from these is more homogeneous than that obtained from the use of mixtures of component metal alkoxides.More recent synthesis of soluble bimetallic oxide-alkoxides like magnesium -oxotetraisopropoxyaluminate has provided an array of novel precursors which are easier to handle due to their lesser tendency of hydrolyzability by atmospheric moisture.Investigations on the mechanism of the reactivity of the above precursors with water as well as methanol (for comparison) and other protic reagents like -diketonates and carboxylic acids are being currently pursued in the research school of Mehrotra.     

Crystal and molecular structure of methylene bis(piperidine-dithiocarbamate), C13H22N2S4

Reaction of anhydrous sodium piperidine dithiocarbamate with methylene chloride yields methylene bis(piperidine dithiocarbamate). The crystals, C₁₃H₂₂N₂S₄ (M=334.57), are monoclinic with space group ,a=6.421(3),b=29.321(7),c=9.022(4)Å,=109.05(3)°,V=1605.6 ų,Z=4,D _c =1.384 g cm^–3,F(000)=712,T=295°K (Mo-K)=0.71069 Å,=5.62 cm^–1 andR=0.032 for 1734 reflections. The molecular structure shows that the methylenic group is bonded to two planar moieties at distances of 1.782(3) and 1.803(3)Å with an S-CH₂-S angle of 114.7(2)°. The configuration about each N atom is planar rather than pyramidal. The two C-N bond lengths adjacent to the C=S bonds are both very short 1.330(4) and 1.336(4) Å indicating the influence of the C=S bond on C-N bond lengths. The six-membered piperidine ring has a classical chair conformation with average C-C distance of 1.511 (5)Å.     

Tetrabromophenolsulphonphthalein as Adsorption Indicator : Volumetric estimation of Silver and Thallium

1.The estimation of iodide and bromide ions in ammoniacal solutions has been described using bromophenol blue as adsorption indicator and the theory of the adsorption indicators has been briefly discussed in the light of the observations. 2.A method has been described by which the silver and thallium ions can be estimated in presence of each other.     

DTA studies on the effect of impurities on the phase transformations of barium carbonate

Orthorhombic () barium carbonate, undergoes a reversible transformation to hexagonal () form around 1093 K which in turn undergoes a reversible transformation to cubic () form around 1253 K. Cationic impurities such as Ca²⁺, Sr²⁺, Cd²⁺, Zn²⁺, have been doped in pure barium carbonate and their effect on the kinetics and energetics of its transformations were studied. By using DTA technique, the enthalpy and energy of activation for the transformation of pure and doped samples of barium carbonate have been calculated and compared.One of the authors (C. R. M. Rao) thanks the University Grants Commission, New Delhi (India), for the award of a research scholarship. The authors are grateful to Dr. I. P. Saraswat, Head of the Chemistry department, for providing the research facilities.     

Cerate oxidimetry : Oxidation of maleic,fumaric, benzoic,salicylic and phthalic acids

1. It has been shown that maleic, fumaric, benzoic, phthalic and salicylic acids can be oxidized completely to carbon dioxide and water by ceric sulphate in the presence of concentrated sulphuric acid. 2. These acids can be estimated quantitatively by the use of ceric sulphate. 3. Acetic and succinic acids are not oxidized by ceric sulphate even in the presence of high concentrations of sulphuric acid.     

Studies on adsorption indicators : Titration of iodide in presence of chloride. mechanism of the colour changes during argentometric titrations with congo red as adsorption indicator

Congo red is a suitable indicator for the titration of iodide in presence of chloride with silver solution at pH 5–5.5. The behaviour of congo red as an adsorption indicator is described in detail. The silver compound of congo red has been isolated and its properties investigated.