摘要:

AbstractThe interaction of bubbles of hydrogen and argon‐oxygen mixtures with liquid lead has been investigated using an oxide solid electrolyte cell of the typewhereOdenotes oxygen, of variable concentrations dissolved in molten lead.Oxygen concentration in molten lead has been varied through bubbling oxidising or reducing gases. The variation in concentration has been obtained by measuring continuously the cell e.m.f. by a recorder. The effects of bubble size and temperature on mass transfer coefficient of oxygen during oxygen dissolution and oxygen removal operations have been studied.The liquid phase mass transfer coefficient increases with decreasing bubble size and increasing temperature. The observed variations agree well with equations available in the literature for low temperature liquid

ISSN:0375-9210    

DOI:10.1002/jctb.2720241002

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractStructural and phase changes of a prepared sample of chromium oxide gel were explored by differential thermal analysis and X‐ray diffraction analysis. Dehydration products were obtained at various temperatures up to 740 °C, by heating in air for 3 hours. Samples obtained by heating below 320 °C were amorphous to X‐rays whereas those obtained at 320 °C, and between 320 and 510°C proved to be a mixture of α‐ and γ‐Cr2O3. However, at temperatures above 510 °C, only one form, the stable α‐Cr2O3exists. The glow phenomenon is attributed to the presence of excess oxygen, resulting from the reduction of Cr(VI) to Cr(III), just prior to the conversion of the amorphous gel to the crystalline γ‐Cr2O3, which is accompanied by a release of energy.Surface area measurements were carried out by cyclohexane, methanol and water adsorption at 35 °C, and the areas were compared with those measured by nitrogen at liquid nitrogen temperature.Pore structure analysis for both micro‐ and mesopores were carried out. The low temperature samples are characterised by the presence of both types of pores, with the micropore fraction predominating acquiring thus the property of molecular sieves; the pores being accessible to water and nitrogen but not to cyclohexane or methanol. At temperatures above 320 °C, the microporosity collapses with the production of a heterogeneous assembly of mesopores. In the mean time the surface changes to be hydrophobic in nature; accordingly it cannot be measur

ISSN:0375-9210    

DOI:10.1002/jctb.2720241003

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractSolid products of the reaction between orthorhombic lead monoxide and cold aqueous lead nitrate solutions in the range of molar proportions 1:3 to 3:1 PbO: Pb(NO3)2have been studied by X‐ray powder diffraction (X.R.P.D.). Three distinct crystalline phases were recognised.Reasonably pure samples of monobasic lead nitrate dihydrate [dilead (II) monoxide dinitrate dihydrate], PbO.Pb(NO3)2.2H2O, were obtained at temperatures below 20 °C when the reactants were in the range of molar proportions 1:3 to 1:1 PbO: Pb(NO3)2. This compound seems to be stable below 20 °C, but it partially dehydrates at higher temperatures. It does not seem to have been reported elsewhere. Monobasic lead nitrate monohydrate [dilead (II) monoxide dinitrate monohydrate], PbO.Pb(NO3)2.H2O, was formed in isolation at temperatures between 25 and 30 °C when the reactants were in the range of molar proportions 1:3 to 1:1 PbO: Pb(NO3)2. This compound is stable at room temperatures, and is identical to phases which have been reported by other authors. Mixtures of these two substances were obtained at temperatures between 20 and 25 °C. Tribasic lead nitrate trihydrate [tetra lead (II) trioxide dinitrate trihydrate], 3PbO.Pb(NO3)2.3H2O, was formed in isolation at all temperatures in the range 15 to 30 °C when the reactants were in the molar proportion 3:1 PbO: Pb(NO3)2. This compound seems to be stable at room temperatures and has been reported elsewhere. When the reactants were in the molar proportion 2:1 PbO: Pb(NO3)2, mixtures of tribasic lead nitrate trihydrate with one or other (or both, depending on the temperature) of the monobasic lead nitrate hydrates were obtained.X.R.P.D. data are given for these three compounds, and a critical assessment is made of all the results in the cases of the two compounds for which published data already exists. Also, it is suggested that compounds of stoichiometries intermediate between that of a monobasic lead nitrate hydrate and that of a tribasic lead nitrate hydrate (and which have been described in the literature) can be only metastable in contact with water. The nomenclature used in this paper follows common industrial practise in naming basic lead compounds. However, scientific names are also given in parentheses when nec

ISSN:0375-9210    

DOI:10.1002/jctb.2720241004

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThermogravimetric analysis has indicated that a convenient range for the study of Zn(COO)2.2H2O dehydration is 120–300 °C, while for pyrolysis it is 320–400 °C. Kinetics of isothermal dehydration and pyrolysis were studied as two consecutive steps in various atmospheres, namely in constant water vapour pressure of 4.8 and 8 mm Hg, in air saturated with water vapour at 25 °C andin vacuo.The kinetic data indicated that dehydration is a pseudo‐first order reaction, which is highly dependent on the surrounding atmosphere. The mechanism of dehydration is either activated diffusion (alternatively surface diffusion) for dehydrationin vacuoor in low water vapour pressures, or activated desorption for dehydration in presence of high water vapour pressure. On the other hand pyrolysis is independent of the prevailing atmosphere, and the energy of activation is of the order of the enthalpy change of the reaction.Earlier studies have involved contact of the dehydrated oxalate with air, or have obscured the influence of the prevailing atmosphere, by dehydrating the sample material at the pyrolysis temperature. These conditions are considered in the present inves

ISSN:0375-9210    

DOI:10.1002/jctb.2720241005

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractA colorimetric method of analysis of azines and isohydrazones which is based on their reaction withp‐dimethylaminobenzaldehyde is discussed. A second method of analysis involving their conversion to hydrazine sulphate has also been developed and excellent agreement between the two methods has been obtained. The colorimetric technique is extremely sensitive, and it was found that at low concentrations the effects of water and ammonia on the calibrations was negligibl

ISSN:0375-9210    

DOI:10.1002/jctb.2720241006

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

摘要:

AbstractThe Mannich reaction product, a dihydrooxazine and a quaternary ammonium salt were prepared in high yield from the model compound 4‐propylguaiacol. When these reactions were extended to the purified kraft lignin, Indulin AT, products were obtained which could remove up to 95% of the colour from kraft whole mill effluent. Flocculation with the lignin derivatives was more efficient at low pH. These materials were less efficient for colour removal than aluminum sulphat

ISSN:0375-9210    

DOI:10.1002/jctb.2720241007

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY

ISSN:0375-9210    

DOI:10.1002/jctb.2720241001

出版商:John Wiley&Sons, Ltd    

年代:1974

数据来源: WILEY