Structural Studies of Analgesics and Their Interactions. V.* The Crystal and Molecular Structure of Metamizol Monohydrate

Metamizol, Na[Ct3H16N3045], C13H16N304S-Na +, a sulphonyl derivative of amidopyrine, is perhaps the most widely used non-narcotic analgetic and antiinflammatory pyrazolone derivative. The monohydrate of the compound crystallizes in the monoclinic space group P2Jc with eight molecules in a unit cell of dimensions a = 9.143 (3), b = 49.50 (2), c = 7.314 (2)/k and fl = 90.9 (1) °. The structure was solved by direct methods and refined to an R value of 0.080 for 4466 observed reflections. The two crystallographically independent molecules in the structure have similar dimensions. The elongated molecules are hydrophobic at one end and hydrophilic at the other with the middle portion partly hydrophobic and partly hydrophilic. The pyrazolone group in the structure has dimensions similar to those found in uncomplexed antipyrine and amidopyrine. The crystal structure can be described as consisting of double layers of metamizol molecules stacked perpendicular to the b axis. The adjacent double layers are separated by a layer of Naions and water molecules.

V2o5-Based Hydrocarbon Sensors

V2O5 supported on ZrO2 is found to be an excellent sensor for n-propane-butane mixtures at 625 K; in-situ X-ray diffraction studies show that V2O5 is reduced to VO2 with a metastable monoclinic structure on contact with the hydrocarbons and is oxidised back to the parent oxide on exposure to air.

A glossary of DNA structures from A to Z

The right-handed double-helical Watson-Crick model for B-form DNA is the most commonly known DNA structure. In addition to this classic structure, several other forms of DNA have been observed and it is clear that the DNA molecule can assume different structures depending on the base sequence and environment. The various forms of DNA have been identified as A, B, C etc. In fact, a detailed inspection of the literature reveals that only the letters F, Q, U, V and Y are now available to describe any new DNA structure that may appear in the future. It is also apparent that it may be more relevant to talk about the A, B or C type dinucleotide steps, since several recent structures show mixtures of various different geometries and a careful analysis is essential before identifying it as a 'new structure'. This review provides a glossary of currently identified DNA structures and is quite timely as it outlines the present understanding of DNA structure exactly 50 years after the original discovery of DNA structure by Watson and Crick

Phase relationships in the system Ni-W-O and thermodynamic properties of NiWO,

The phase diagram of the Ni-W-O system at 1200 K was established by metallographic and X-ray identification of the phases present after equilibration at controlled oxygen potentials. The oxygen partial pressures over the samples were fixed by metered streams of CO+CO2 gas mixtures. There was only one ternary oxide, nickel tungstate (NiWO4), in the Ni-W-O system at a total pressure of 1 atm, and this compound decomposed to a mixture of Ni+WO2.72 on lowering the oxygen potential. The Gibbs' free energy of formation of NiWO4 was determined from the measurement of the e.m.f. of the solid oxide galvanic cell, Pt, Ni+NiWO4+WO2.72/CaO-ZrO2/Ni+NiO, Pt and thermodynamic properties of tungsten and nickel oxides available in the literature. For the reaction, NiO(s)+WO3(s)rarrNiWO4(s) DeltaG°=–10500–0.708 T (±250) cal mol–1.

Solid State Electrochemical Sensors in Process Control

The basic principles of operation of gas sensors based on solid-state galvanic cells are described. The polarisation of the electrodes can be minimised by the use of point electrodes made of the solid electrolyte, the use of a reference system with chemical potential close to that of the sample system and the use of graded condensed phase reference electrodes. Factors affecting the speed of response of galvanic sensors in equilibrium and non-equilibrium gas mixtures are considered with reference to products of combustion of fossil fuels. An expression for the emf of non-isothermal galvanic sensors and the criterion for the design of temperature compensated reference electrodes for non-isothermal galvanic sensors are briefly outlined. Non-isothermal sensors are useful for the continuous monitoring of concentrations or chemical potentials in reactive systems at high temperatures. Sensors for oxygen, carbon, and alloying elements (Zn and Si) in liquid metals and alloys are discussed. The use of auxiliary electrodes permits the detection of chemical species in the gas phase which are not mobile in the solid electrolyte. Finally, the cause of common errors in galvanic measurements, and tests for correct functioning of galvanic sensors are given. 60 ref.--AA

Observation of the doubling of critical exponents in reentrant phase transitions

Electrical resistance (R) measurements are reported for ternary mixtures of 3-methylpyridine, water and heavy water as a function of temperature (T) and heavy water content in total water. These mixtures exhibit a limited two-phase region marked by a loop size (ΔT) that goes to zero as the double critical point (DCP) is approached. The measurements scanned the ΔT range 1.010°C less-than-or-equals, slant ΔT less-than-or-equals, slant 77.5°C. The critical exponent (θ), which signifies the divergence of ∂R/∂T, doubles within our experimental uncertainties as the DCP is reached very closely.

Bioleaching of sulphides under applied potentials

The influence of applied DC potentials on the activity and growth of Thiobacillus ferrooxidans, as well as on the dissolution behaviour of some base metal sulphides is discussed with reference to bioleaching. Selective bioleaching of zinc from sphalerite could be achieved under an applied potential of −500 mV (saturated calomel electrode) from binary mineral mixtures containing the zinc mineral and chalcopyrite or pyrite. On the other hand, bioleaching of pyrite and chalcopyrite was found to be enhanced under positive potentials of +400 mV and +600 mV, respectively. Probable mechanisms in the electrobioleaching of sulphides are examined with respect to galvanic, microbiological and applied potential effects.

Calorimetry In Vapor Absorption And Binary Mixture Vapor Compression Refrigeration And Heatpump Systems

The use of binary fluid systems in thermally driven vapour absorption and mechanically driven vapour compression refrigeration and heatpump cycles has provided an impetus for obtaining experimental date on caloric properties of such fluid mixtures. However, direct measurements of these properties are somewhat scarce in spite of the calorimetric techniques described in the literature being quite adequate. Most of the design data are derived through calculations using theoretical models and vapour-liquid equilibrium data. This article addresses the choice of working fluids and the current status on the data availability vis-a-vis engineering applications. Particular emphasis is on organic working fluid pairs.

Combustion Synthesis of Metal Chromite Powders

Fine-particle metal chromites (MCr2O4, where M = Mg, Ca, Mn, Fe, Co, Ni, Cu, and Zn) have been prepared by the combustion of aqueous solutions containing the respective metal nitrate, chromium(III) nitrate, and urea in stoichiometric amounts. The mixtures, when rapidly heated to 350°C, ignite and yield voluminous chromites with surface areas ranging from 5 to 25 m2/g. MgCr2O4, sintered in air at 1500°C for 5 h, has a density of 4.0 g/cm3.

Combustion synthesis of rare earth cuprates

Rare earth cuprates, La2CuO4 Nd2CuO4, La1.8M0.2CuO4 (M=Ca.Sr) and Nd1.85Ce0.15CuO4 have been prepared by the combustion of redox mixtures containing corresponding metal nitrates and maleic hydrazide, C4H4N2O2, at 350°C. The solid combustion products are submicron size amorphous powders which on heat treatment (700°C, 30 minutes) yield crystalline single phase cuprates. Strontium doped lanthanum cuprate, La1.8Sr0.2CuO4, shows an onset of superconductivity at 36K.

Behaviour of the curve of critical exponents near and away from a double critical point

To investigate the nature of the curve of critical exponents (as a function of the distance from a double critical point), we have combined our measurements of the osmotic compressibility with all published data for quasibinary liquid mixtures. This curve has a parabolic shape. An explanation of this result is advanced in terms of the geometry of the coexistence dome, which is contained in a triangular prism.

Combustion Synthesis and Properties of Fine Particle Spinel Manganites

Fine particle spinel manganites have been prepared by thermal decomposition of the precursors N2H5M1/3Mn2/3(N2H3COO)3 · H2O (M = Co and Ni) and M1/3 Mn2/3(N2H3COO)2 · 2H2O (M = Mg and Zn), as well as by the combustion of redox mixtures containing M(II) nitrate (M = Mg, Co, Ni, Cu, and Zn), Mn(II) nitrate, and maleic hydrazide (MH) in the required molar ratio. Both the precursor and redox mixtures undergo self-propagating, gas-producing, exothermic reactions once ignited at 250-375°C to yield corresponding manganites in less than 5 min. Formation of single phase products was confirmed by X-ray powder diffraction patterns. The manganites are of submicrometer size and have surface area in the range 20-76 m2/g.

Field-dependent changeover from current-to voltage-limiting characteristics by non-linear n-type BaTiO3 ceramics

Non-linear resistors having current-limiting capabilities at lower field strengths, and voltage-limiting characteristics (varistors) at higher field strengths, were prepared from sintered polycrystalline ceramics of (Ba0.6Sr0.4)(Ti0.97Zr0.03)O3+0.3 at % La, and reannealed after painting with low-melting mixtures of Bi2O3 + PbO +B2O3. These types of non-linear characteristics were found to depend upon the non-uniform diffusion of lead and the consequent distribution of Curie points (T c) in these perovskites, resulting in diffuse phase transitions. Tunnelling of electrons across the asymmetric barrier at tetragonak-cubic interfaces changes to tunnelling across the symmetric barrier as the cubic phase is fully stabilized through Joule heating at high field strengths. Therefore the current-limiting characteristics switch over to voltage-limiting behaviour because tunnelling to acceptor-type mid-bandgap states gives way to band-to-band tunnelling.

Folding of a Donor-Containing Ionene by Intercalation with an Acceptor

Cationic ionenes that bear electron-rich 1,5-dialkoxynaphthalene (DAN) units within the alkylene segment were allowed to interact with different types of electron-deficient, acceptor-containing molecules in an effort to realize intercalation-induced folding of the ionenes; the collapse of the chains was expected to occur in such a way that the donor and acceptor units become arranged in an alternating fashion. Several acceptor-bearing molecules were prepared by the derivatization of pyromellitic dianhydride and naphthalene tetracarboxylic dianhydride with two different oligoethylene glycol monomethyl ether monoamines. This yielded acceptor molecules with different water solubility and allowed the examination of solvophobic effects in the folding process. UV/Vis spectroscopic studies were carried out by using a 1:1 mixture of the DAN-ionenes and different acceptor molecules in water/DMSO solvent mixtures. The intensity of the charge-transfer (CT) band was seen to increase with the water content in the solvent mixture, thereby suggesting that the intercalation is indeed aided by solvophobic effects. The naphthalene diimide (NDI) bearing acceptor molecules consistently formed significantly stronger CT complexes when compared to the pyromellitic diimide (PDI) bearing acceptor molecules, which is a reflection of the stronger pi-stacking tendency of the former. AFM studies of drop-cast films of different ionene-acceptor combinations revealed that compact folded structures are formed most effectively under conditions in which the strongest CT complex is formed.

Surface tension of some binary organic solutions of alkylbenzenes and 1-alkanols

The surface tensions of binary mixtures of 1-alkanols (Cl-Cd with benzene, toluene, or xylene were measured. The results were correlated with the activity coefficients calculated through the group contribution method such as UNIFAC, with the maximum deviation from the experimental results less that 5%. The coefficients of the correlation are correlated with the chain length.