Oxidation of aldehydes by aqueous Ce (IV) in nitric acid

The kinetics of oxidation of acetaldehyde (at 20°, 31° and 40° C.), propionaldehyde (at 15°, 25° and 35° C.) and chloral hydrate (40°, 50° and 60° C.) by ceric nitrate in nitric acid medium [(H⁺) ≈ 0 · 5?1 · 5 M] were studied. The reactions were followed by determining rates of ceric disappearance for variations in [Ce⁴⁺], [RCHO], [H⁺], μ, temperature, etc. The stoichiometry, ΔCe⁴⁺ / Δ CH₃CHO ≈ 2 was established. The reactions were found to be 2nd Order—first order each with respect to [Ce⁴⁺] and [RCHO]. No complex formation between Ce⁴⁺ and aldehydes was observed. Neutral Ce (NO₃)₄ (H₂O)₂ and diol of the aldehyde were assumed the active species. The rate and thermodynamic data were calculated and discussed. The rates of oxidation were correlated with the structures of the aldehydes.     

Thermal expansion of ferroelectrics

Using the interference method the thermal expansion of lithium hydrazinium sulphate [Li(N₂H₅)SO₄] has been investigated in the temperature range ?170° C. to +220° C. The principal expansion coefficients along the crystallographic axes have been determined and at room temperature (25° C.) the values ofa _a,a _b anda _c are respectively 17·7, 13·5, and 43·0, ×10^?6 (°C.)^?1. The expansion coefficients are found to vary nonlinearly, and, in particular, along thec-axis the thermal expansion shows an anomalous behaviour between ?160°C. and ?60°C. and also in the neighbourhood of +130°C. These anomalies are explained as due to homomorphous transitions in which there is a reorientation of the ?NH ₊ ³ group about the N-N axis or a re-alignment of the ?NH₂ group.     

Heating effect of BaTiO3 in microwave field and microstructure of BaTiO3

Microwave equipment at 2 450 MHz was employed to prepare BaTiO₃. The heating effect of the system in the microwave field, which was influenced by several factors including dielectric properties of synthesis system and thermal insulate structures, was discussed in detail. The heating rates of the synthesis system were mainly determined by BaCO₃ and TiO₂ at low temperature and by TiO₂ and BaTiO₃ at high temperature. The results show that the heating effects in microwave field are greatly different from those in conventional furnace. The reaction of BaCO₃ and TiO₂ only lasts for 3 min at 1 100°C, and the fine, narrow-distributed and well-crystallized powders were prepared. Project supported by the National Natural Science Foundation of China.     

Transition phenomena at saturation temperature studies on electrolytic conductance of alkali halides in aqueous systems

A plot of negative logarithm of the electrical conductance (K)vs reciprocal of the absolute temperature (T) shows the existence of the transition in the systems ‘Electrolyte-Sucrose-water’, ‘Electrolyte-Mannitol-water’, and ‘Electrolyte-Xylose-water’. A saturated solution of sucrose/mannitol/xylose containing a known amount of an electrolyte was prepared at a temperature of 50·0±0·05° C and the crystals were separated by centrifugation at the same temperature. The conductance of the centrifugate was measured in a tubular conductivity cell at different temperatures in the range between 30° C to 70° C. The plot of ?log₁₀ Kvs 1/T showed a break at the saturation temperature, the point where two straight lines appeared to intersect. The transition can be explained on the basis of change in the water structure due to the presence of ‘structure-breaking’ and/or ‘structure-making’ ions. These sucrose, xylose, and mannitol molecules due to the presence of a number of hydrogen bonding sites contribute largely toward the build up of big structures in the supersaturated state. These structures crumble as the system undergoes the transition at the saturation temperature. Different electrolytes produced more or less similar effect.     

Magnetic properties and microstructure of HDDR isotropic Nd-Dy-Fe-Co-B bonded magnets with high coercivity

The effect of small amount of Co and Dy addition on the magnetic properties of HDDR isotropic Nd-Dy-Fe-Co-B bonded magnets was investigated. The experimental results show that the intrinsic coercivity H_cj and the reversible temperature coefficient of remanence of (Nd_0.65 Dy_0.35)_12.5-(Fe_0.9Co_0.1)₈₁B_6.5 magnet were 1.53 MA·m^-1(19.3 kOe) and -0.059%/°C (25–155°C), respectively. The high coercivity and low temperature coefficient of the magnet are due to the enhanced anisotropy field, increased Curie temperature and improved microstructure by Dy and Co addition.     

Interdiffusion and adhesion at the inteface of a polystyrene-poly(2,6-dimethyl-1,4-phenylene oxide) blend below the glass transition temperature

Experiments on adhesion between the film surfaces of a polystyrene (PS)-poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) blend were carried out below the glass transition temperature of the bulk (T _g ), at T=T _g −13 and T=T _g −23°C. The contact time varied from 2 to 1440 min. The strength at the interface was then measured at room temperature. The strength at the blend-blend interface was calculated using an additive diffusion model which takes into account the strength at homopolymer-homopolymer interfaces (PS-PS, PS-PPO, and PPO-PPO), surface concentration of components, and its variation with depth. A fair agreement between the calculated and measured strength was found. The results of the study support the concept of decreasing glass transition temperature near the surface of polymer glasses as compared with T _g of the bulk. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 5, pp. 661–670, September–October, 1999.     

Synthesis of C3N4 crystals under high pressure and high temperature

C₃N₄ crystals with the size of several micrometers have been synthesized from C₃N₄H₄ in the presence of nickel-based alloy or cobalt as catalyst under high pressure of 7 GPa and temperature of about 1400°C for 10 min. Scanning electron microscopy, energy-disperse X-ray analysis, and X-ray diffraction were used to examine the grown crystals. The general rule on selecting the starting materials for synthesis of carbon nitride crystals at high pressures and high temperatures is suggested.     

Experimental study of scaling properties and roughing mechanisms in C60-Ag thin films

Surface morphologies and microstructures of C₆₀/Ag composite films were studied by atomic force microscope (AFM) and transmission electron microscope (TEM). The surface roughness depended on the substrate temperature, and the transition of surface morphology of rough→smooth→rough was observed when the substrate temperature increased from −50 to 120°C. Although the rms values are similar, the scaling properties of the thermal roughing and the kinetic roughing surfaces are quite different. The relations between the scaling properties, microstructures and roughing mechanisms are discussed based on the AFM and TEM results. Project supported by the National Natural Science Foundation of China (Grant No. 59529204).     

Anomalous double wave of cobalt (II) in aqueous thiocyanate medium

In neutral thiocyanate medium at low temperatures (0–5°C) cobaltous ion produced an anomalous double wave of nearly equal height. This behaviour was ascribed by earlier workers to a stepwise reduction of cobaltous ion in this medium. A study of the effects of temperature and height of the mercury column as well as the influence of the concentrations of cobalt and thiocyanate on the waves showed that the processes were controlled by chemical reaction and adsorption. It has been concluded that the first wave is a surface kinetic wave resulting from the reduction of [Co(H₂O)₄(SCN)₂] and the second step is a post-adsorption wave brought about by the adsorption of [Co(H₂O)₅SCN]⁺ species on the electrode.     

Temperature dependence of the photoelastic behaviour of crystals—Part I

A modified form of Filon’s spectrometer method is used to study the variation of the stress-optical constants (q ₁₁-q ₁₂) andq ₄₄ of KCl, KBr, KI, LiF, MgO and NaCl in the temperature range 30° C. to 400° C. It is found that (q ₁₁-q ₁₂) andq ₄₄ generally increase numerically with the increase of temperature except those of NaCl which show a decrease. In KBr and KI,q ₄₄ first increases and then decreases numerically. The potassium halides show an interesting gradation of variation of these constants. In all the crystals studied, which are of NaCl type, the variation in (q ₁₁-q ₁₂) is greater than that inq ₄₄. Mueller’s ultrasonic method is used for measuring the ratio of strain-optical constantsp ₁₂/p ₁₁, in the temperature range 30°C. to 250°C. Combining the results obtained by these two methods, the absolute strain-optical constantsp ₁₁ andp ₁₂ have been evaluated at different temperatures. Curves are given showing the variation ofp ₁₁ andp ₁₂ with temperature. The variation ofp ₁₁ andp ₁₂ with temperature is discussed in terms of the contributions of the various factors considered by Mueller in his theory of photoelastic effect in cubic crystals.     

Optical absorption of Co2+ doped NH4Cl: Phase transformation studies

The absorption spectrum of Co²⁺ doped NH₄Cl has been studied from the room temperature to the liquid nitrogen temperature. A sudden change in the spectrum is observed between 243° K and 233° K which is attributed to the phase transition in the crystal. From the observed spectrum it is suggested that Co²⁺ goes in interstitially as well as substitutionally. Both the types of centers exist at room temperature, but with decrease in temperature substitutional ions migrate to interstitial sites, the process being stimulated at the phase transformation point so that the 77° K spectrum seems to be mostly due to the interstitial centers. The 77° K spectrum is analyzed in the approximation of octahedral symmetry for interstitial ions and the band positions are fitted fairly well with B = 870 cm.^?1 Dq = 850 cm.^?1 and C = 4·4 B. A blue shift of about 100 cm.^?1 is observed for⁴T₁ (P) band at the phase transition which is attributed to the increase in Dq value with the anomalous lattice contraction at the phase transition. The decrease in the lattice parameter calculated from this blue shift is around 0·4% which is in good agreement with the results of X-ray measurements. Two possible models for the interstitial complex are examined and the one with fourfold chlorine coordination associated with two neutral water molecules at the first neighbour (NH₄)⁺ site lying along < 100> direction is suggested to be more probable.     

Oxidation studies

Studies on oxidation of water by cobaltic ions in perchloric, nitric and sulfuric acid media in the temperature range 20–30° C. at constant ionic strength of 2·2 M were carried out. An overall order of 3/2 for cobaltic ion concentration was observed in perchloric, nitric acid media and at low [Co³⁺]<4×10^?3 M in sulfuric acid medium. At high [Co³⁺] in sulfuric acid medium an order 2 was observed. In all the three acid media an inverse dependence of the rates on [H⁺] was noticed. From the experimental results, an acid-independent reaction path was inferred in perchloric and nitric acid media. The effect of ionic strength, HSO ₄ ^? and initially added cobaltous ions as well as temperature was studied. Suitable reaction schemes were suggested to explain the experimental results and activation energy values for some of the rate parameters were evaluated. Kinetic studies on oxidation of tertiary amyl and tertiary butyl alcohols in sulfuric acid medium and that of the former in perchloric acid medium were carried out. The reaction rates were found to vary linearly with [Co³⁺] and [Alcohol]. From the effect of acidity and of [HSO ₄ ^? ] in H₂SO₄ medium on the reaction rates it was concluded that in HClO₄ medium CoOH²⁺ species were the active entities while in H₂SO₄ medium Co³⁺ as well as CoOH²⁺ species were the active entities. The influence of ionic strength, temperature, etc., on the raction rates were studied and activation energy values for some rate constants were evaluated.     

Epitaxial growth and electrical transport properties of La0.5Sr0.5Co03 thin films prepared by pulsed laser deposition

Epitaxial growth of the La_0.5Sr_{0.5 3}(LO) thin films has been realized on Lin3, SrTiC₃ and MgO substrates by pulsed laser deposition. The epitaxial growth behavior and the electrical transport properties of these films were studied systematically. The temperature dependencies of the resistivity of the film have been determined. Studies indicate that close dependencies exist between the crystal structures and the electrical transport properties of the epitaxial LSCO films, and that the epitaxial thin films are of low resistivity and metallic conductive features. The epitaxial films deposited on the LaA10₃ substrates at about 700 °C possess the optimal properties compared with the others. Discussions of the dependencies and the mechanisms of the epitaxial structures on the electrical transport properties of the LSCO films have been made. Project supported by the National Natural Science Foundation of China (Grant No. 19574003 and No. 19674001).     

Vinyl polymerization

Polymerization of Acrylamide initiated by cobaltic ions in aqueous solution at 15° C. and 20° C. in HClO₄ and H₂SO₄ media have been studied. Kinetics have been followed by determining the rate of cobaltic ion disappearance as well as monomer disappearance with variations in cobaltic, monomer and hydrogen ion concentrations, temperature, ionic strength, etc. Besides polymer reaction it has been observed that side reactions like water oxidation and monomer oxidation also contribute to rate of cobaltic ion disappearance. Certain anomalous results in H₂SO₄ medium have been observed. A reaction scheme involving CoOH²⁺ and Co³⁺ as initiators in HClO₄ and H₂SO₄ media respectively and mixed termination—mutual and linear—has been suggested. Certain rate parameters involving rate constants for initiation, propagation, termination and the corresponding activation energies have been evaluated.     

The new physiology of vision

α-Nitroso-β-naphthol was successfully employed for the gravimetric determination of Mercury (ii) (as nitrate) and in its separation from copper (ii). The former was percipitated at pH 1·9 and the latter at pH 11·00. The precipitate could be dried to constant weight at 110° C. The composition of the complex was established by analysis to be Hg (C₁₀H₆NO₂)₂ 20 mg. of mercury could be estimated with an error of ± 0·3% in pure solutions. Appreciable amounts of copper could be removed in alkaline medium without co-precipitation of mercury. The error was ±0·5%.     

Liquid structure of undercooled Cu70Ni30 alloy

Experiments of X-ray diffraction for liquid Cu₇₀Ni₃₀ alloy above and below its liquidus (l 230°C) have been carried out. By the analysis of experimental results, it is discovered that difference between structures of liquid and undercooled Cu₇₀Ni₃₀ alloy is their cluster sizes. The correlation radius of cluster is 1.125 nm and the atom number of cluster is 403 at l 250—l 400°C, and they are 1.3 nm and 704 respectively at the undercooled liquid state (1 200°C). The structure of liquid Cu₇₀Ni₃₀ alloy is fcc short order and its solid structure, fcc, is kept from liquid fcc short order.     

Paramagnetic resonance of Gd3+ in SmCl3·6H2O single crystals

The Paramagnetic Resonance of Gd³⁺ in SmCl₃·6H₂O single crystals, grown from solution, is studied at room temperature. A six line spectrum for H//Z and a seven line spectrum for H//X corresponding to ΔM=± 1 transitions are observed. Their angular variation in ZX plane from?=0° to?=90°, is studied and the spin-Hamiltonian analysis is presented. The probable amount of admixture of the next higher electronic state⁶P_7/2 with the ground state⁸S_7/2 is also estimated.     

Fundamental regular semigroups with inverse transversals

Let C be a regular semigroup with an inverse transversal C° and let C be generated by its idempotents. Following W. D. Munn and T. E. Hall’s idea, in this paper, a fundamental regular semigroup T _C,C° with an inverse transversal T _C,C° ^° is constructed such that the following holds. For any regular semigroup S with an inverse transversal S° and 〈E(S)〉 = C, C° = C ∩ S°, there is a homomorphism φ from S to T _C,C° such that the kernel of φ is the maximum idempotent-separating congruence on S, and φ satisfies: (1) φ| _C is a homomorphism from C onto 〈E(T _C,C°)〉 ; (2) φ| _S° is a homomorphism from S° to T _C,C° °. In particular, S is fundamental if and only if S is isomorphic to a full subsemigroup of T _C,C°. Our fundamental regular semigroup T _C,C° is isomorphic to a subsemigroup of the Hall semigroup of C but it is easier to handle. Its elements are partial transformations, and the operation—although not the usual composition—is defined by means of composition.     

Oxidation studies

The results on the kinetics of oxidation of HCHO and some alcohols,viz.,n-propanol, allyl alcohol, cyclohexanol and benzyl alcohol by ceric nitrate in nitric acid medium in the temperature range of 10–35° C. are presented. The active form of Ce⁴⁺ during the oxidation of the above organic substrates was assumed to be the neutral Ce(NO₃)₄. The mechanism of oxidation and thermodynamic parameters for the above compounds are also given.     

Thermal study of some manganese oxide and hydrous oxide minerals

The minerals manganite, pyrolusite, ramsdellite, cryptomelane, psilomelane, braunite, lithiophorite and woodruffite from Sandur manganese ore deposits, Bellary District, Mysore State, which have been investigated by microscopic, chemical and X-ray methods (Naganna, 1963) are subjected to thermal study through differential thermal analysis and gravimetric thermal analysis. The hydrous oxides of manganese undergo dehydration below 400° C. and subsequent changes follow later. Most of the minerals containing MnO₂ thermally react in two stages, one at about 600° C. and the other beyond 800° C. The thermal behaviour of pyrolusite is seen to be similar to that ofβ MnO₂, while the thermal behaviour of ramsdellite is found to be similar to those ofα orγ MnO₂. Further the study suggests that ramsdellite may change over to pyrolusite below 500° C.