摘要:

AbstractUranyl carbonate may be reduced to uranium dioxide with formaldehyde sulphoxylates (preferably the ammonium salt) or a mixture of formaldehyde and a bisulphite. The mechanism of the reaction is discussed.

ISSN:0021-8871    

DOI:10.1002/jctb.5010130301

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe effect of water vapour on the oxygen permeability of Cellophane laminates has been measured. A dimensionally stable coating can restrain the swelling of a water‐sensitive substrate to give a greater oxygen barrier than expected from the sum of the component barriers. This is discussed particularly for Saran on Cellophane. The permeability apparatus that has been designed depends on a commercial Pirani gauge. This allows accurate measurement and is very versatil

ISSN:0021-8871    

DOI:10.1002/jctb.5010130302

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe surface activities of lime and magnesia from different sources are compared in relation to the changes in crystal structure during preparation at several temperatures up to 1000°. The activity of calcium oxide from the hydroxide is increased in the presence of calcium peroxide, which initially produces (mon)oxide to nucleate the hydroxide crystallites before they decompose. Calcium nitrate gives activated calcium oxide at 500°, but melts with decomposition at higher temperatures, producing comparatively large lime crystals.Magnesium hydroxide and carbonate (magnesite) give magnesia which is correspondingly more active than the lime obtained from calcium hydroxide and carbonate in previous investigations. This is due mainly to the greater volume decreases associated with the crystal changes, and to the diminished sintering of the magnesia at the lower decomposition temperatures.The most active product is obtained from magnesium oxalate which decomposes directly to magnesium oxide. Much less active oxide is produced from magnesium salts of monobasic organic acids, e.g., formate and acetate, which require reaction between separate anions for decomposition.The effect of sintering on the temperature limitations for applying magnesium oxide catalysts to organic dehydration and dehydrogenation reactions is discusse

ISSN:0021-8871    

DOI:10.1002/jctb.5010130303

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractMagnesium oxide samples differing widely in surface activity (specific surface 10–180 m.2g.−1) have been ‘dry’ hydrated by exposure to water vapour at 22° and ‘wet’ hydrated by liquid water at 22° and 95°.The rates of hydration differ considerably, the reaction generally proceeding inwards from the outside of each oxide crystallite by an advancing interface mechanism. Changes in surface area and crystal structure resemble those during the hydration of lime. The more active magnesias age (agglomerate) rapidly in both ‘dry’ and ‘wet’ hydrations, unless the relative water vapour pressures are low; even then, the very slow completion of the hydration ultimately produces considerable ageing.The less active magnesias ‘dry’ hydrate slowly like the less active limes, with splitting of the larger original crystallites increasing the total number present. ‘Wet’ hydration at 22° proceeds with some ageing of the hydroxide, even during the earlier stages and this becomes much greater later. At the higher hydration temperature, 95°, the product ages more rapidly, but the much greater hydration rate produces a time lag in the recrystallisation of the newly‐formed magnesium hydroxide to its normal structure. Later, expansion splits the aged material as the recrystallisation is completed, with the hydration becoming slow and irregular. Magnesias and limes prepared from their respective carbonates at 1000° therefore sho

ISSN:0021-8871    

DOI:10.1002/jctb.5010130304

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractSamples of calcium, strontium and barium carbonates differing widely in surface activity have been prepared by calcining the oxalates, formates and acetatesin vacuoand in air at a series of temperatures between 300° and 600° or 650°.Decomposition of the organo‐metallic salts results in several‐fold increases in specific surface, especiallyin vacuo, as the newly‐formed carbonates recrystallise to very small individual crystals having the normal lattice structure. The products of maximum activity are obtained at or near the temperature at which decomposition is practically completed within the fixed time (5h.). The activity of the carbonate obtained from each oxalate is usually much higher than that from the corresponding formate and acetate, which require preliminary reaction between separate anions before decomposition.The activated carbonates all sinter on further calcination, the calcium carbonate sintering more rapidly than the strontium carbonate and still more so than the barium carbonate. Hence, calcination at the higher temperatures ultimately produces barium carbonate of greater activity than strontium carbonate and calcium carbonate.The reactivities of the carbonates in the ketonisation of acetic acid vapours are compared and discussed in relation to the temperature co

ISSN:0021-8871    

DOI:10.1002/jctb.5010130305

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe evolution of hydrogen chloride during the pyrolysis of certainB‐trichloro‐N‐triarylborazoles, (ClBNAr)3, at temperatures up to about 500°, points to the formation of boron‐carbon bonds, thereby effecting polycondensation. Formation of arylamine hydrochloride and arylaminoboron dichloride and infra‐red studies point to borazole‐ring fission, and polycondensation in a linear sense. The polymeric residue, liquid above about 300°, was a hard solid at room temperature, soluble in certain organic solvents, but was susceptible to hydrolysis. The material became solid above 500°, and was then insoluble and of considerable hydrolytic and oxidative stability.Replacement of chlorine in the chloroborazoles by alkyl groups, hydrogen, amino and alkylamino groups is considered with reference to hydrolytic stability and future pyr

ISSN:0021-8871    

DOI:10.1002/jctb.5010130306

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

摘要:

AbstractThe effects of temperature, detergents, electrolyte, agitation and fabric structure on the removal from cotton of octadecane, tripalmitin, stearyl alcohol and stearic acid labelled with carbon‐14 have been studied. The following mechanisms appear to be operative in the removal of these materials: (1) the rolling‐up mechanism; (2) mesomorphic phase formation; (3) soap formation; (4) break‐up of polycrystalline aggregates.In general, the addition of electrolyte in the presence of surface‐active agents increases the amount of fatty soil removed. The magnitude of the electrolyte effect depends on (a) the degree of ionisation, (b) the pH of the solution and (c) the valency of the added cation.By means of a chopped fibre technique it has been possible to show that about 35% of the fatty soil is held on the surface of the threads, about 30% between the fibres of which the threads are composed, about 30% inside the tubular fibres while about 5% is held in the fibrile structure of the

ISSN:0021-8871    

DOI:10.1002/jctb.5010130307

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY

ISSN:0021-8871    

DOI:10.1002/jctb.5010130308

出版商:John Wiley&Sons, Ltd    

年代:1963

数据来源: WILEY