Three-dimensional electrohydrodynamic temporal instability of a moving dielectric liquid sheet emanated into a gas medium

A linear electrohydrodynamic instability analysis is presented for an inviscid dielectric liquid sheet emanated into an inviscid dielectric gas medium in the presence of a horizontal electric field. The influence of Weber number, gas-to-liquid density ratio, and the applied electric field on the evolution of two-, and three-dimensional disturbances of symmetrical and antisymmetrical types is studied. It is found, for antisymmetrical waves, that two-dimensional disturbances always prevail over three-dimensional disturbances, regardless of Weber number or gas-to-liquid density ratio values, especially for long waves; while for short waves, both two- and three-dimensional disturbances grow at approximately the same rate. It is also found, for symmetrical waves, that two-dimensional disturbances always dominate the instability process at low Weber number, and when the Weber number is large, symmetrical three-dimensional disturbances become more unstable than two-dimensional ones for long waves. The effect of increasing the gas-to-liquid density ratio is to promote the dominance of long three-dimensional symmetrical waves over their two-dimensional counterpart. Finally, the equilibrium Weber number at which the growth rates of two- and three-dimensional modes are equal is discussed for both symmetrical- and antisymmetrical-disturbances cases.-1     

Gas chromatographic analysis of xylidine isomers on heteroaromatic compounds

Summary Nicotinic acid, picolinic acid, isonicotinic acid, histidine and other amphoteric heteroaromatic compounds, uracil, thymine, isatin and other heteroaromatic compounds having imino and carbonyl groups as well as IH-benzotriazole, benzoguanamine and guanidine phosphate effectively resolved all the xylidine (dimethylaniline) isomers. Furthermore, the mixed phases of nicotinamide + p-amino-benzoic acid and melamine+barbituric acid also provided an appreciable resolution. These analyses were carried out using a support which were not treated with an alkali.     

Structure-retention correlations of hydrocarbons in gas-liquid and gas-solid chromatography. Cycloalkenes and cycloalkadienes

Summary The retention indices of cycloalkenes and cycloalkadienes with C₆–C₁₃ rings are determined by gas-liquid chromatography (GLC) on glass capillary columns coated with OV-1 and Ucon LB 550X and by gas-solid chromatography (GSC) on a microcolumn packed with uncoated graphitized thermal carbon black (GTCB). Structure — retention correlations are derived on using index differences such as H^OV, H^GTCB and ΔI values, considering the differences in the stereochemistry of these compounds. It is shown that the combined application of index increments obtained in GLC and GSC provides more detailed structure informations. The value of the retention index units agree with the most stable conformations of the alicyclic compounds. The high value for the energy equivalent to an index unit (ΔG_I.U.=4.18kJ/mol) confirmes that graphitized thermal carbon black causes much stronger dispersive interactions than any nonpolar liquid phase. Dedicated to Prof. Dr. E. sz. Kováts (Ecola Polytechnique Fédérale de Lausanne) on the occasion of his sixtieth birthday.     

Some observatons on the derivations of solvent polarity factors from gas-liquid partition coefficients

Summary The derivation by Snyder of polarity parameters from gas-liquid constants for 81 solvents has been re-examined. It is shown that the correction for the influence of the molecular size of the solvents and solutes by means of the Flory-Huggins entropy expression is more successful than the original correlation as carried out by Snyder. The correction for dispersive and/or entropic contributions to the free energy of transfer in the original treatment is found to be inadequate. However, the effect of various more refined treatments on the final polarity parameters P, x_e. x_d and x_n is probably small.     

Gas-liquid flow hydrogenation of nitroarenes: Efficient access to a pharmaceutically relevant pyrrolobenzo[1,4]diazepine scaffold

Using a Tube-in-Tube device based on the amorphous Teflon AF-2400 fluoropolymer, a series of nitroarenes was hydrogenated to afford the corresponding aniline compounds. The system was then applied to the construction of a pyrrolobenzo[1,4]diazapene scaffold through a tandem hydrogenation-condensation-hydrogenation sequence.     

The Gas Chromatography of Diene Tricarbonyl Iron Complexes

Abstract

Successful gas chromatographic elution of a range of diene tricar-bonyl from complexes has been achieved for the first time. Provided that precautions were taken to exclude air and prevent prolonged exposure to light many of those supposedly ‘unstable’ compounds could be gas chroma-tographed at temperatures up to 150[ddot] with no apparent thermal decomposition. Teflon columns employing E-301 methyl silicone gum as stationary phase gave best results, symmetrical gausssian peaks being obtained for most compounds with quantitative response to the microgram level.     

Electrohydrodynamic instability of a dielectric compressible liquid sheet streaming into an ambient stationary compressible gas

The effect of compressibility of fluids on the linear electrohydrodynamic instability of a dielectric liquid sheet issued from a nozzle into an ambient dielectric stationary gas in the presence of a horizontal electric field is investigated. It is found that increasing the Mach number from subsonic to transonic causes the maximum growth rate and the dominant wavenumber of the disturbances to increase, and the increase is higher in the presence of the electric field. Liquid compressibility has been found to have a minimal effect on instability. At constant wavenumber and electric field values, the growth rate of disturbances increases as the gas Mach number tends to 1, and then begins to decrease with further increase in the gas Mach number. At small values of wavenumber, antisymmetrical disturbances grow faster than symmetrical ones, while the growth rate of both types of disturbances approach each other at large wavenumbers, which increases by increasing the electric field values. At small Weber numbers, antisymmetrical disturbances exhibit a higher maximum growth rate and a lower dominant wavenumber than symmetrical disturbances. However, the maximum growth rate and dominant wavenumber of the two types of disturbances are almost identical when both Weber number and electric field values become large. An increase in the gas to liquid density ratio enhances the instability, and this effect is enhanced for high electric field values. Surface tension and electric fields always oppose and increase the development of instability, respectively; and they have opposite effects for long wavelengths and high Weber numbers.