摘要:

AbstractThe following equation, which is derived from an expression previously obtained for liquid‐liquid extraction columns by Dell&Pratt (1951), and which is basically similar to the equation of Bertetti (1942), is proposed for the correlation of flooding rates for packed absorption and distillation columns:This equation can be reduced to a form resembling the graphical correlation used by Sherwood, Shipley&Holloway (1938). A comparison with the available experimental data shows that agreement is good up to a critical value of the group on the right, beyond which the exponent changes sharply to to − 0·20. Derived values of the constantsC2are given for four types of packing, and the applications and limitations of the equation are discu

ISSN:0021-8871    

DOI:10.1002/jctb.5010020801

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe extraction of carbon disulphide from its solution in benzene by means of sodium hydroxide solution is a first‐order reaction with respect to the carbon disulphide content, and appears to be diffusion‐controlled (E= 3·43 kcal.). The rate of extraction is a function of the extent of mixing, the sodium hydroxide concentration, and temperature; the rate may be increased appreciably by the addition of a wetting agent and/or glycol, sucrose or mola

ISSN:0021-8871    

DOI:10.1002/jctb.5010020802

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractIt has been found that a closely coiled spring wound as a single layer on a central core of sealed Pyrex tubing, and with its adjacent turns separated by one or more turns of a loosely coiled spring, constitutes an efficient packing for fractional distillation. To secure a good fit between the packing and the outer Pyrex tube of the column the latter is shrunk on the packing under vacuum by gently heating with a hand torch, using the air blast only.

ISSN:0021-8871    

DOI:10.1002/jctb.5010020803

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe mechanical properties of thermoplastics are strongly interdependent and sensitive to changes of temperature and straining rate. These and other, less general, factors have an important bearing on the choice of testing techniques which can very often not merely be taken over from the established metal‐testing practice. These points are discussed in detail, taking a few tests on the acrylic thermoplastic Perspex (polymethyl methacrylate) as instances. Some numerical values of the properties of Perspex in compression, tension, fatigue and impact are also given, mostly in graphical for

ISSN:0021-8871    

DOI:10.1002/jctb.5010020804

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractIn certain circumstances steel coated with aluminium paint can emit sparks when struck with a metal striker, and such sparks may ignite mixtures of inflammable gases or vapours in air. The sparks are due to the thermite reaction between iron oxide and aluminium, and therefore are produced only in the presence of iron oxide. The extent of this hazard depends on the nature of the paint; it is increased if the painted steel is subjected to heat.This work was therefore carried out to determine the effect of the nature of the paint, and the temperature to which the paint might be subjected in use on the tendency to produce incendive sparks (i.e. those liable to ignite inflammable gases or vapours).The investigation was divided into two sections, the first dealing with certain preliminary studies on the conditions necessary for the production of sparks and the reaction involved in spark formation, and the second consisting of a survey of the possible hazard with a representative series of commercial paints.No exact correlation between paint composition and liability to emit sparks was obtained, but none of the commercial oil‐bound paints tested gave sparks unless the specimen had been heated to at least 150°.The paper includes a note by the Senior Chemical Inspector of Factories, outlining the practical application of the resul

ISSN:0021-8871    

DOI:10.1002/jctb.5010020805

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe strength and water‐absorption characteristics of three types of soil stabilized with resorcinol/formaldehyde resin have been investigated. The effects of varying (1) the resin concentration, (2) the age of the mixture, and (3) the concentration of added hydrated lime on these characteristics have been examined. The influence of (1) and (3), and of temperature and the presence of certain soil constituents on the setting time of the resin has also been studied.Small proportions (1 to 10%) of the resin were found to increase the seven‐day strength and reduce the water absorption of the compacted soils. Setting of the resin was accelerated by the addition of hydrated lime and by increasing the temperat

ISSN:0021-8871    

DOI:10.1002/jctb.5010020806

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractIn order to find out the correct size required for heat exchangers, waste‐heat boilers, gas coolers, etc., heat‐transfer coefficients are needed. Although the available literature provides us with the most recent formulae for these coefficients it is nevertheless difficult to assemble all the technical data of the required dimensions. This is especially tedious for those who deal only occasionally with the subject.The physical and chemical properties of the gases are given partly in British and partly in metric units. Thus the inevitable conversion needed to reduce all the figures to the one system of measurement requires much time and study if mistakes are to be avoided. Furthermore, the values given for the thermal conductivity of gases differ in a remarkable degree in the various available lists which, also, ignore many of the more recent valuable experimental figures.The writer has therefore prepared charts for the rapid determination of heat‐transfer coefficients and the presentation of new data based on recent experimental figures for the thermal conductivity of single gases and of gaseous mixtures. These charts are applicable to the gases commonly used in ind

ISSN:0021-8871    

DOI:10.1002/jctb.5010020807

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe facts concerning the solvent action of organic substances on polyacrylonitrile have been collected from diverse sources and new observations have been made. A new relationship between the boiling points of organic compounds and their latent heats of evaporation has been devised which is more accurate than the Hildebrand function, and this, together with new calculations and measurements of latent heats of evaporation, has been used to elucidate the relationship between the cohesive energy densities (C.E.D.) of organic compounds and their solvent power for polyacrylonitrile.All solvents for polyacrylonitrile are highly polar in character. Most of the best solvents have very high C.E.D.s in the neighbourhood of 220 to 230 cal./c.c. A separate calculation shows that this is approximately the C.E.D. of the polymer. It is believed that the molecules of such solvents have no greater attraction for the polymer molecules than they have for their own kind, solution being brought about by the increase in entropy.N‐Disubstituted amides, and probably cyclic sulphones possess strong solvent action at lower C.E.D.s (116–170 cal./c.c.), and this is probably because the molecules of these substances have a slightly greater attraction for the polymer molecules than they have for their own kind. Most strongly hydrogen‐bonded substances, such as alcohols, phenols, carboxylic acids, unsubstituted amides, and monosubstituted open‐chain amides are non‐solvents at all levels of C.E.D. The powerful attraction of the molecules of such substances for each other is not matched by an equally powerful attraction for the polymer molecules, and solution cannot therefore take place. In some cases these hydrogen‐bonded substances make a strong contribution to the solvent power of mixtures.If the C.E.D. of the polyacrylonitrile is reduced by interpolymerization with a polymerizable hydrocarbon, solvents such as open‐chain esters, ketones, and mono‐reactive nitriles possessing lower C.E.D.s will attack it. This shows that ketones, open‐chain esters, and mono‐reactive nitriles fail to dissolve polyacrylonitrile because none of these substances possesses the necessary high C.E.D. The failure is not due to their polar groups having less attraction for the nitrile groups of the polymer than they have for their own kind.A modified equation for linking solvent power with the C.E.D. of the solvent in a semi‐quantitative manner has been devised. This contains an arbitrary constantK, but the value of this varies only

ISSN:0021-8871    

DOI:10.1002/jctb.5010020808

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY

摘要:

AbstractThe kinetics of the oxidation of sulphur dioxide with oxygen using a commercial vanadium pentoxide catalyst has been investigated. Experimental conditions have been chosen such that the reaction has been carried out isothermally in a flow‐type reactor at temperatures (360° to 450°) and conversions (up to 10%) where the reverse reaction may be ignored.The results, analysed in conjunction with the relevant adsorption isotherms and rates of adsorption on the clean catalyst, indicate that the rate‐determining step is the rate of reaction between gaseous oxygen and chemisorbed sulphur dioxide.The adsorption isotherms, which are Langmuir in character, indicate the presence of at least two different types of active centres. Both oxygen and sulphur dioxide are reversibly chemisorbed, oxygen being weakly bound with a heat of adsorption of 6·4 kcal. and sulphur dioxide strongly bound with a heat of 28·8 kcal. There is evidence that both adsorbed species possess considerable mobility on the surface.Measurements of the rates of adsorption of SO2and O2on the clean surface indicate that oxygen is adsorbed by a second‐order mechanism at a slower rate than the observed rate of reaction, whereas sulphur dioxide is adsorbed by a third‐order mechanism at a much faster rate than the rate of reaction. Adsorption equilibrium of SO2may be assumed, under the conditions of reaction, without sensible error.Adsorption‐rate measurements of both SO2and O2indicate that the number of active centres (defects) increases with temperature, according to a relationship of the type d lnL/dT = A/RT2whereL= no. of active centres, as suggested by Volkenstein (1949).With SO2, reaction between it and an active centre requires no activation energy, the increase in rate with increase in temperature being due entirely to the increase in the number of active centres. With O2, a small activation energy may be required, although the main increase in rate of adsorption with temperature is similarly due to the increase in the number of active centres with temperature.Some interesting comparisons are made between the results of these adsorption measurements and recent work on the semi‐conductivity of oxide catalysts, notably by Bevan&Anderson (1950) and Garner, Gray&Stone (1950). Several points of similarity are noted which indicate lines for further work.Finally, a mechanism for the catalytic oxidation of sulphur dioxide is proposed, the main feature

ISSN:0021-8871    

DOI:10.1002/jctb.5010020809

出版商:John Wiley&Sons, Ltd    

年代:1952

数据来源: WILEY