ISSN:0021-8871    

DOI:10.1002/jctb.5010140808

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractWhen a metal is oxidised in carbon dioxide, the growth of oxide film may be accompanied by the deposition of carbon which may return to the gas phase as carbon monoxide, remain in the oxide film or dissolve in the metal. Isotopic tracer techniques with carbon‐14 provide a simple method by which the amount of carbon deposition may be measured, and they also provide a unique method by which the fate of this carbon may be determined. The current experimental techniques are outlined and numerical values are given, with illustrative results, for the oxidation of beryllium, of a 20/25/niobium austenitic steel and of chromiu

ISSN:0021-8871    

DOI:10.1002/jctb.5010140801

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe kinetics of oxidation processes in the system carbon monoxide‐sulphur dioxide‐oxygen in the presence of surfaces, mainly vanadium pentoxide (V) and equimolar V2O5and K2SO4(V‐K), have been investigated using a static system. The upper limit of the explosive combustion of ‘wet’ CO was the same with aV, V‐K, KC1 or silica surface, the overall activation energy governing ignition being about 35 kcal. mole−1. Ignition was promoted by the addition of water (or the use of a boric oxide surface) but inhibited by SO2and packing the vessel. The lower limit pressure was higher with aV‐ than with aV‐K‐surface, but varied little with temperature, and was unaffected by varying the water concentration or by the addition of SO2. Increase in surface/volume ratio raised the limit. The rate of the normal slow oxidation of ‘wet’ CO at pressures above the upper limit was very sensitive to changes in the nature of the surface, the order beingV‐K>silica>V>KC1. Addition of SO2greatly decreased the rate with aV‐surface but increased it with aV‐K‐surface. Packing the vessel had the same effect and with aV‐K‐surface the activation energy fell to about 18 kcal. mole−1. The heterogeneous reaction of SO2and O2was much faster on aV‐K‐ than on aV‐surface, the activation energies being 31 and 27 kcal. mole−1respectively.The elementary steps in the chain mechanism, occurring in the systems under moist conditions, are discussed. It is concluded that, at the lower limit, branching is due to excited CO2and termination to surface destruction of oxygen atoms, while, at or above upper limit pressures, branching by a process involving O atoms and H2O and the relative rates of reaction of HO2radicals in the gas phase and at the wall are important. The mixtures undergoing ‘inhibited’ slow oxidation probably contain carbon, suboxides which can terminate chains by reaction with O atoms. SO2may react with O atoms in the gas phase or

ISSN:0021-8871    

DOI:10.1002/jctb.5010140802

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractNew kinetic data are presented for the reaction between ammonia and formaldehyde to form hexamethylenetetramine. The reaction appears to be first‐order in ammonia concentration, and second‐order in formaldehyde concentration, according to the results of flow experiments made with a single stirred‐tank reactor. Both concentrated and dilute solutions were investigated. Heat of reaction data are also rep

ISSN:0021-8871    

DOI:10.1002/jctb.5010140803

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractThe techniques of gas‐solid chromatography have been widely used for measuring heats of adsorption. It is theoretically possible to derive information concerning the adsorption kinetics from the same chromatographic data and the present report deals with this application of chromatography. The process of adsorption in a packed column of adsorbent is visualised as resulting from molecular collisions with the external surface of the porous adsorbent particles. Only a fraction α of the total collisions results in adsorption. The adsorbed molecules, on the average, spend a finite time, θ, in the adsorbent particle. For n‐butane on silica gel at 60°, θ is proportional to the 3/2 power of the particle diameter and varies from 1·8 to 13·8 sec, for samples having median diameters of 0·192 to 0·712 mm., respectively. For a given particle size, θ is proportional to eΔH/RT(ΔHis the heat of adsorption) and amounts to abou

ISSN:0021-8871    

DOI:10.1002/jctb.5010140804

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractAmorphous silica accelerates the hydration rate of 3CaO,SiO2. This acceleration can be explained by assuming that the silica, by lowering calcium‐ and hydroxyl‐ion concentrations during the first minutes of the hydration, increases the conversion rate of a first protective hydrate layer into another less protective one.In Portland cement pastes, not only hydration of alite but also consumption of sulphate are accelerated, as judged by calorimetric experime

ISSN:0021-8871    

DOI:10.1002/jctb.5010140805

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractReplacement of tetravalent manganese in calcium metamanganate (CaMnO3) by trivalent iron, and of tetravalent titanium in calcium titanate (CaTiO2) by trivalent iron and aluminium has been made. In each case it was found possible to obtain continuous replacement up to a limit of 50%. The pseudo‐cubic perovskite cells of CaMnO2and CaTiO3became genuinely cubic for greater than 25% replacement, and the cubic lattice parameters were measured at 50% replacement. Oxygen deficiencies of about one in twelve must exist in the 50% replacement compounds to maintain the ionic charge balanc

ISSN:0021-8871    

DOI:10.1002/jctb.5010140806

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY

摘要:

AbstractRecent studies in these laboratories of the sorption of n‐paraffins (in the C4—C20range) in specially treated 5A molecular sieves have revealed that both temperature and molecular weight have somewhat unexpected effects on the isotherms determined by a McBain spring balance method (at 300–400°). The results do not agree with predictions in the literature that, with increasing carbon number, the isosteric heats of sorption should rise at a constant rate. Above C10, − ΔHdecreases, temperature dependence becoming almost zero in the region C15—C20. The results are compared with the limited amount of published data, and discussed in terms of the configuration of the sorbed molecules, and of unusual entropy effects. The deductions are supported by some measurements, also reported, for the sorption of nC8—nC17

ISSN:0021-8871    

DOI:10.1002/jctb.5010140807

出版商:John Wiley&Sons, Ltd    

年代:1964

数据来源: WILEY