摘要:

AbstractThe effects of micro‐organisms on rubbers and plastics are reviewed, with reference to the chemical nature of the polymers and their possible additives. The confused and sometimes contradictory nature of the evidence is indicated, and it is concluded that both synthetic and naturally‐occurring polymers are attacked but it is not possible at this stage to say which chemical groups in each polymer are suscepti

ISSN:0021-8871    

DOI:10.1002/jctb.5010180701

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractBurial tests on plasticised PVC in neutral soil inoculated with species ofPseudomonasandBrevibacteriumhave shown degradation in 8 weeks that is largely dependent on the nature of the plasticiser. There was no evidence for any attack on the polymer itself. Phthalate and phosphate plasticisers were resistant; adipate, azelate and sebacate plasticisers were susceptible and a number of others, e.g. chlorinated hydrocarbon and epoxy types, occupied an intermediate position. The degree of attack was also dependent on the nature of the stabiliser used in the PVC formulation, lead‐based stabiliser conferring less resistance than barium/cadmium‐based stabiliser. Degradation has been assessed in terms of loss in weight, change of stiffness and loss of energy during cyclic deformat

ISSN:0021-8871    

DOI:10.1002/jctb.5010180702

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractReactions of lime and magnesia with magnesium chloride and sulphate have been studied in relation to industrial processes, namely, extraction of magnesium from sea‐water and production of Sorel‐type cements. Variations in phase composition, surface area and crystallite and aggregate sizes of the products have been correlated with experimental conditions.The solid limes react rapidly with the more dilute magnesium salt solutions, and the precipitated magnesium hydroxides are much more finely‐divided. Basic magnesium salts initially formed are decomposed subsequently to hydroxide as the pH becomes stabilised at higher values. Greater concentrations of magnesium chloride give more extensive basic salt formation and prevent all of the lime going quickly into solution. Similar products are given with solid magnesium hydroxide and magnesium chloride and sulphate solutions.The Sorel‐type cements obtained from magnesium oxide and the more concentrated chloride solutions set appreciably, even before loss of surface through final ageing. They show two distinct phases: (a) irregular grains of 10–50 μm diameter, and (b) acicular or tabular crystals up to 20μm long, mainly in radiating growths. By contrast, the magnesium oxysulphate crystals are not so elongated and the cements set with considerable loss of surface area, giving interlocking structures in which 20–50 μm‐diameter grains are often ‘fused’ together as larger 4

ISSN:0021-8871    

DOI:10.1002/jctb.5010180703

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractRates of calcium exchange between solid and solution in the ageing of hydrated lime and of calcium carbonate samples have been determined using calcium‐45 radio‐isotope. After a comparatively rapid calcium uptake of about 1 molecular layer at the hydrated lime surface, the exchange rate diminishes as the ions need to diffuse more deeply into the hydrated lime structure. Results for calcium carbonate samples of widely different specific surfaces are compatible with very slow ageing in water.Rates of gypsum precipitation from radioactive calcium chloride and nitrate solutions have been compared in neutral and acidic media and in the presence of albumen. Lower gypsum saturation ratios are established ultimately in neutral rather than acidic media, particularly in solutions containing no salts other than gypsum.Solid hydrated lime reacts rapidly with dilute sulphuric acid, aluminium and magnesium sulpnates, magnesium chloride or sea‐water, releasing calcium ions into solution. The radioactivities of the solutions decrease subsequently as gypsum separates out or calcium ions are adsorbed by the finely‐divided magnesium hydroxide precipitated. At higher magnesium salt concentrations, the calcium‐45 radioactivity does not initially increase so sharply. This is ascribed to basic salt formation preventing all of the lime from going quickly into

ISSN:0021-8871    

DOI:10.1002/jctb.5010180704

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe distribution of hydrochloric acid between water and 40 vol.‐% solutions of tri‐n‐butyl phosphate (TBP) in six diluents and also between water and 20. 40 and 60 vol.‐% solutions of TBP in odourless kerosene and pure TBP at 20°, 30° and 50° has been studied to find the effects of temperature, diluent and TBP concentration on the extractability of hydrochloric acid and on third‐pha

ISSN:0021-8871    

DOI:10.1002/jctb.5010180705

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractA study has been made into the effects of a low frequency semi‐corona discharge on carbon disulphide, ethyl mercaptan, amyl mercaptan and thiophene present as 1–2% sulphur/hydrocarbon mixtures. Semi‐corona discharge, which was carried out at atmospheric pressure, has resulted in the partial desulphurisation of the sulphur‐containing hydrocarbon mixtures. The efficiency of the desulphurisation was influenced by the techniques employed and by the nature of the central electrode. In almost all instances the reactions were accompanied by the formation of solid m

ISSN:0021-8871    

DOI:10.1002/jctb.5010180706

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractPrecipitates of strontium carbonate (10−3mole litre−1) were floated using dodecylpyridinium chloride, hexadecylpyridinium bromide, hexadecyltrimethylammonium chloride and a dialkyldimethylammonium chloride. Flotations were performed at a gas flow‐rate of 7 litre hour−1for 3 minutes or 2 litre hour−1for 20 minutes. Complete recoveries were possible by both methods, provided optimum concentrations of collector were used. If too little collector was present, redispersion of precipitate occurred because the foam formed was insufficient to support it. With too much collector, the precipitate was excluded from the bubbles and also became coated by a double layer of collector which gave a hydrophilic surface.Increase of temperature and of time allowed for precipitation, improved recoveries because of increased particle size. Flotations were not complete below 10−3m unless the strontium carbonate was co‐precipitated in calcium carbonate, when 10−8m could be recovered. Increased ionic strength reduced recoveries because it caused precipitation to be slower, attachment of collector to the precipitate to be less secure, flotation of the collector to be more rapid and foam drainage, and hence redispersi

ISSN:0021-8871    

DOI:10.1002/jctb.5010180707

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

摘要:

AbstractThe ion‐exchange properties of algal particles fromA. nodosumhave been investigated. The Ca/H ion‐exchange rate at hydrogen ion concentration 0·1 n was shown to be strikingly lower, while the selectivity coefficentK caHwas about ten times higher, forA. nodosumthan forL. digitataandL. hyperboreastipe particles. LogK caHshowed a marked decrease with increasing calcium equivalent fraction in the algal particles. The higher Ca/H selectivity of algal particles fromA. nodosumwas shown to be the cause of the observed difference in exchange rate between this alga and the two other species.The ion‐exchange rate Ca/H for 36–52 mesh particles fromA. nodosumat hydrogen ion concentration 0·1 n was governed by a film‐diffusion mechanism and the diffusion of calcium through a thin liquid film enveloping the particles was suggested as the rate‐determining step. The rate was particle‐diffusion controlled for 10–20 mesh particles. The exchange rate for 36–52 mesh particles increased strongly as the hydrochloric acid concentration was increased from 0·05 to 1 n; this exchange appeared to proceed like a second order reaction at 0·05 n and showed a gradual change to a first o

ISSN:0021-8871    

DOI:10.1002/jctb.5010180708

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY

ISSN:0021-8871    

DOI:10.1002/jctb.5010180709

出版商:John Wiley&Sons, Ltd    

年代:1968

数据来源: WILEY