摘要:

AbstractA method is described whereby viscosity changes in a system may be followed tachometrically. Changes of phase, gelling points and similar phenomena accompanied by sudden large changes in viscosity may be rapidly located. The technique is of wide application, especially in the field of colloid science; although it is empirical in nature, approximate values for absolute viscosities may be obtained, if desired, by calibration against standard liquids.

ISSN:0368-4075    

DOI:10.1002/jctb.5000690701

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractThe strength of laminated plastics derives mainly from the fibrous reinforcement, but the fibres, being arranged in layers, cannot contribute to the interlaminar strength. The consequent weakness is revealed by a low cross‐tensile strength and a low shear strength parallel to the laminations. Three methods of test which have been used pith laminates ¼ in thick are described and compared with material greater than ¼ in. in thickness, two additional tests may be employed.Certain variables in the preparation of phenolic‐bonded laminates are shown not to be critical, but interlaminar of strength in common with other properties of reinforced plastics is sensitive to variations in the moisture content of the impregnated reinforcement at the time of pressing.The interlaminar strength of voidless products made from a phènol‐formaldehyde resin in alcoholic solution with absorbent paper or scoured fabrics is substantially constant over the range of resin content likely to be used in practice. With both types of reinforcement the limiting strength of the resin itself is approached—but not fully attained—at a resin content of 27%. There is no essential difference between the strengths obtained with scoured fabrics or absorbent paper.The beneficial effects of desizing and scouring are conclusively proved. While the scouring process used does not appear to be highly critical, desizing by itself is not an adequate pre‐treatment. Absence of twist in the threads of a fabric does not contribute to higher interla

ISSN:0368-4075    

DOI:10.1002/jctb.5000690702

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractIt is important that accurate control of operating variables should be maintained throughout a long batch fractionation. This can best be achieved in many distillations by automatic control. In the laboratory still and acccssorics hcrc described, automatic control is provided for the maintcnancc of adiabatic cons in the fractionating column, the adjustment of reflux ratiofto give optimun: fractionation cfficicncy )and the :hourly) changing of rcccivcrs in which distillate is collected! All :hourly)thcsc operations are controllcd by a modified Multclec.' Tempcnture Recorder. This instrument also provides a rccord of the important temperatures and opcntions throughout the distillaiion. An cxamplc is givcn of the use of this still in the fnctionation of a commcrcial iso‐octan

ISSN:0368-4075    

DOI:10.1002/jctb.5000690703

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractIn a high‐efficiency laboratory fractionating eoIumn, the control of the temperature of the jacket is of considerable importance and the hcat input .may require frequent adjustment. It simple(and rclatively cheap) nutomatic device is described which makes use of air thermometers as the temperature‐sensitic. celements The pressurc difference between two thermometers alters aJercury level and makes electrical contacts which switch the heater on or off by means of a re

ISSN:0368-4075    

DOI:10.1002/jctb.5000690704

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractThe mechanical propcrtics of a plasticized polymer are gencnlly admitted to depend to a large extent on the viscosity of the plasticizer. It is shown that the tempernture dependence of the viscosity of a plasticizer may be less than that of a polymer, and that the addition of a plasticizer to a polymer may reduce the sensitivity of the systcm. This conclusion is in opposition to a common interpretation of the viscosity thcory of plasticizer action, but is shown to bc in accordance with experiment.

ISSN:0368-4075    

DOI:10.1002/jctb.5000690705

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractIn view of the dangers said to attend the use of acetaldehyde in industrial processes, the sensitiveness to ignition of acetaldehyde vapour in admixture with air or oxygen was investigated. In the first series of experiments, case of ignition was measured by the minimum temperature at which spontaneous ignition occurred on admitting the gas mixture into a glass or metal‐lined tube kept at a specific temperature. This being a common method of determining ignition temperatures, the results could be compared with published data on other inflmmable gases and vapours. The experiment was carried out with mixtures of acetaldehyde and air or oxygen distributed over the range of maximum sensitiveness in each case. The most sensitive mixtures of acetaldehyde with air were those containing 30–60% of acetaldehyde, the lowest ignition temperature recorded being 176deg; c. in an aluminium tube; the most sensitive mixtures with oxygen contained 60–80°, of acetaldehyde, the minimum ignition temperature being 105° c. in glass or aluminium tubes. The results thus show that acetaldehyde is among the most dangerous of industrial solvents in respect of ignition by hot surfaces.In the second series of experiments, case of ignition was measured by the minimum current in the primary circuit of an induction coil which, on interruption, would produce between standard electrodes sparks which were capable of igniting the gas mixture. This being an arbitrary test, comparative tests with other explosive gases and vapours were also included. The most sensitive mixture of acetaldehyde and air in this test contained approximately 8%, of acetaldehyde. Compared with other inflammable gases and vapours, acetaldehyde did not appear unduly sensitive to ignition by a transient source of heat of this nature.These experiments indicate that the liability of acetaldehyde mixtures to accidental explosion in industrial operations is more likely to be due to a low ignition temperature than to exceptional sensitiveness to fugitive sources of heat such as electrical or frictional sparks. The formation of peracetic acid during the pre‐ignition oxidation of acetaldehyde could account for a number of the phenomena observed, and the explosive decomposition of peracetic acid round 110° c. may be responsible for the exceptionally low ignition temperatures of certain acetaldehyde—oxy

ISSN:0368-4075    

DOI:10.1002/jctb.5000690706

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractIn order to assess, and possibly find a method of reducing, the explosion huard in the manufacture of acetic acid from acetalde‐hyde, a knowledge was required of the range of acctaldehyde‐oxygen‐nitrogen mixtures capable of propapating flame under wrious conditions. The limits of inflammability in such mixtures were therefore determined for upward, horizontal and downward !lame‐propagation in glass tubes of I‐, 2‐ and 3‐in. diameter at room temperature and at sooC. The effect of contamination with carbon dioxide, acetylene and acetic acid was also examined, as well as that of using aluminium tubes in place of glass. The range of inflammability in the acetaldehydroxygen‐nitrogen system is exceptionally wide and offers little hope of eliminating explosion risks in the manufacture of acetic acid, the best safeguard being to minimize free space and place suitable guards at vulnerable points.The results show that in acetaldehydc∼∼gen‐nitrogen mixmres, the lower limit is mainly a function of the acetaldehyde content, whereas the upper limit is mainly determined by the oxygen content; this suggests that the calorific value Of the gas is an important factor in limit propagation. Another important factor in the case of acetaldehyde is the apearancc of the ‘cool’ flame. This causes a marked extension of t!e upper limit, from which it is inferred that the products of ‘cool’ flame combustion are incompletly oxidized, the main constitue

ISSN:0368-4075    

DOI:10.1002/jctb.5000690707

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY

摘要:

AbstractIn cxpansion joints two forms of jointing matcrial are required : (i) a pre‐formed joint filler which provides a spaccr between adjacent slabs to accommodatc expansion of the concrctc; (ii) a scaling compound, filling the top inch or so of the joint, which is intcndcd to prevent the entry of water and grit. In contraction joints, a scaling compound only is rcquircd. The desirable propcr‐ties of prc‐formed joint fillcrs and of joint‐scaling compounds are discussed. Thc main rcquiremcnt of joint fillcrs is that they shall bc compressible, and thcre appears to be no problem in providing satisfactory matcrials; soft wood, fibrc‐board, cork and cellular rubber have all been uscd succcssfully. No satisfactory scaling compound has yet been cvolvcd. The desirable propcrrics of scaling compounds have been dcfincd by laboratory tests in conjunction with road experiments and it is considcrcd that scaling compounds should be satisfactory from the following aspccts: (i) case of application; (ii) adhesion to concrctc; (iii) cxtcnsibility at low tcmpcraturcs on the road; (iv) resistance to flow at high temperatures on the road; (v) rcsistancc to the ingress of grit; (vi) weathering and ageing. Tests havc bcen dcvclopcd at the Road Rcscarch Laboratory to examine the more important of thcsc aspccts and standards for satisfactory road performance are rccommcndcd. Gcncral dcscriptions are given of the properties of the different types of scaling compound availablc. Thc most satisfactory compounds at prescnt availablc are rubbcr‐bitumens. Most scaling compounds are hot‐poured and it is considered that there can bc littlc furthcr improvement in the performance of materials which are poured in a hot fluid condition. The advantagcs and difficultics of cold‐applied scaling compound

ISSN:0368-4075    

DOI:10.1002/jctb.5000690708

出版商:John Wiley&Sons, Ltd    

年代:1950

数据来源: WILEY