摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. The Fnraday Society is not vespoztsible for opinions extressed before i t by Authors or Speakers.transactions Chc Sarabap 5ocietp. OF FOUNDED 1903. T O PROMOTE THE STUDY OF ELECTROCHEMISTRY, ELECTROMETALLURQY, CHEMICAL PHYSICS, METALLOGRAPHY, AND KINDRED SUBJECTS. VOL. xx. DECEMBER, I 924. PART 2. PHYSICAL AND PHYSICO-CHEMICAL PROBLEMS RELATING TO TEXTILE FIBRES. A GENERAL DISCUSSION. A joint meeting of the FARADAY SOCIETY and the TEXTILE INSTITUTE was held at the British Empire Exhibition, Wembley, on Wednesday, June I Ith, 1924, when a GENERAL DISCUSSION took place on ( ( PHYSICAL AND PHYSICO-CHEMICAL PROBLEMS RELATING TO TEXTILE FIBRES” PART I. Chairman :-Sir Robert Robertson, K.B.E., F. R.S., President of the Faraday Society. Dr. W. Lawrence Balls, Sc.D., F.S.S. (The Fine Cotton Spinners’ and Doublers’ Association), delivered the following In- troduction to the proceedings.Received May 2 7 th, I 9 2 4. The field of physical research in relation to the textile industries is sharply demarcated into two portions-one dealing with the physical pro- perties of the unit components of the textile, the other dealing with the inter-relationships between these components. (a) PhyszcaZ Prujerties of fhe TexfiCe Unit.-The unit from the textile point of view may be taken as the single hair or fibre, the question as to the nature of the unit in the physical sense being put aside by stating that it must necessarily be the atom.2 24 PHYSICAL AND PHYSICO-CHEMICAL PROBLEMS Study of the physics of these textile units is necessarily closely coupled with biology; and this to a greater extent than is commonly recognised, since nearly all the fibres and hairs employed in textile work are of plant or animal origin. The physical properties of such hairs and fibres largely depend on their growth history, and are more easily understood if this is studied concurrently. In illustration we may quote the case of cotton, which was formerly regarded as impure cellulose ; then as a cell wall ; then as a colloid ; and now as a structure which includes all the previous de- scriptions.One might insist on the importance of working with single units in the study of these properties, and not merely with masses of units, though the importance of “ single hair ” technique is more generally realised than it used to be. As a consequence of this, there develops the need for statistical treatment throughout by which to evaluate the nature and degree of variability from unit to unit.(b) Inter-reZationsh$ of the Unit Components.-We are not aware that any attempt has previously been made to generalise the peculiar form which physical problems take in this field. For convenience we may formulate the position, with some exaggeration, as follows : That one dimensional units (hairs and fibres) are built up into two dimensional structures (yarns and fabrics) for use in three dimensions. The study of such a system of inter-related units would appear to fall into a study of its statics and dynamics ; but it is doubtful whether any strictly static treatment is possible with the existing textiles. The “ creep ” displayed as between one unit and another of the complex, together with the ‘‘ set ” that individual units undergo, practically prohibits anything more than first approximations being obtained on static considerations.For ex- ample we may take a case where the tensile strength of yarn is unaffected by variations up to 2000-fold in the length tested. Or we may take, again, the fact that it is possible to eliminate some of the twist from a strand of yarn, although both ends remain firmly clamped, and are restored to their original position. It would seem that the dynamic treatment of the subject must be ap- plied at every point, in lap or sliver, yarn or cloth. Such treatment is par- ticularly important industrially in the attempt to obtain even distribution of the units in the drafting process.This process, it should be noted, is fundamental to every textile industry (other than silk and artificial silk), whether it is effected by hand or by the roller motion invented by Wyatt in 1745. If we imagine ourselves viewing the oncoming sliver as it is being drafted, it consists of a set of points; but these points paradoxically have each an enormous surface. There is no parallel outside the textile indus- tries to the class of phenomena produced by this exaggeration of the properties of the material in one direction only. The writer proposed the term ‘‘ Trichodynamics ” in 1918, on the analogy of Aerodynamics, to indicate this peculiar field of study. ConcZusion.-The defects of yarn and fabrics which admittedly exist, together with other defects whose existence is not even recognised, were formerly due to faults in the machinery employed.Many of these have been eliminated in the course of time ; and the physicist is now concerned rather with studying the causation of defects which are inherent in the pro- perties of the raw material. The utility of the scientist in industry is largely conditioned by the degree of stability of the industry; and where conditions, methods, and objects are changing-as they appear to be tending to change in textiles-the slow translation of experience by the225 RELATING TO TEXTILE FIBRES practical man lags behind the rate of advance required. Rapid accumula- tion of knowledge can only be made by experiments carried to the reductio ad absurdurn in all directions. In the course of some additional comments, Dr.Balls said he had been interested to find that practically every paper to be read at this meeting dealt with the first of the two halves into which he had divided the field to be covered, viz., the properties of the fibres themselves. I t was the second part of the subject, however, which was the most complicated, and offered the most difficult field for study, a field which was peculiar to textiles and was still practically untouched. As regards the first part, during ten years’ experience in the cotton industry, and ten more in cotton growing, he had often seen the beneficial effect of a little dose of biology here and there, and the manner in which it helped non-biologists to get round corners where otherwise they would have been stuck for a very long while.The point which he wished to impress in this connection was that the properties of the textile unit could not be tackled without dealing with its previous history, i.e. with the growth of the composite structure. In the case of cotton that had been a very marked feature indeed, and it happened that cotton was now the best known of all units from this point of view. The second part of the field for investigation appeared when one left the study of the individual unit and turned to the inter-relationships of the various units building up the yarn or fabric, and that was almost an unexplored field. I t was, however, an aspect fundamental to the textile industries and, in a sense, the thing making the textile industries worth the attention of the physicist. From the scientific point of view there was the most wonderful material for study in the inter-relationships of these peculiar units.When one started to examine the properties of fabrics or yams all sorts of aberrations were immediately found. On the idea of the strength of the chain being in its weakest link, one would imagine that the testing of a longer Iength of yarn (at the same rate of loading) would give a greater chance of discovering the weaker links and also give a measure of the frequency of occurrence of the weaker links in the chain. Most of them, however, probably knew that that was not the case. There was one extreme instance within his experience in which the length of the thread had been varied from 10 cm. to 12,000 cm. and the breaking load had remained unaffected.That, of course, was an extreme case but it de- monstrated the fact that rigid reasoning was not applicable and that there were a good many more variables in the proposition than was commonly supposed. Most of the faults in cotton yarns to-day were faults intrinsic in the physical properties of the raw materials (ie. in the textile units themselves) rather than faults in machinery and things of that character ; the difficulty was to locate these properties in the raw material and measure them. When an industry was changing its technique, as the electrical industry always was and the textile industry was now beginning to do, the scientist’s place was very different from what it was in a stable industry, and the main reason why a scientist could be useful to an unstable industry-an industry which was going through a process of change or evolution-was that the practical man took a very long time to get the answer in ex- perimental work.The scientist was trained in experimental work and he ought to be able to get his answer more quickly (so that was nothing226 PROBLEMS RELATING TO TEXTILE FIBRES to his credit), but the chief reason for the slowness of the practical man in getting at the answer was that he was always afraid to experiment off the deep end, and would not try the reductio ad absurdurn. He would put in one per cent. more twist or 2 per cent. more t*ist and, perhaps, take three or four years to feel his way to the final result. On the other hand, the scientist given the same problem, who did not know the kind of twist he should use, would try the experiment to the extreme in both directions at the first attempt. To use a gunner’s term, he would quickly straddle the final result. On the assumption that the textile industry was in for a series of changes, not only had the physicist an extremely interesting field to explore in which he could be of use to the industry but, in course of time, the industry would find that his services were indispensable. In conclusion, Dr. Balls said it was a great pleasure to him to open the discussion because in the early days of the Research Associations, and even sooner, he had backed physics as the winning horse for industrial research in the textile industry. He had come long ago to the decision quite definitely, that the pivotal subject for industrial research in the textile industries during the next half century was that child of the Cavendish Laboratory, and outcast of practical men, the study of physics.

ISSN:0014-7672    

DOI:10.1039/TF9242000223

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. 226 PROBLEMS RELATING TO TEXTILE FIBRES THE STRUCTURE OF LINEN CLOTH FOUND IN THE TOMB OF TUT-ANKH-AMEN. BY ALEXANDER SCOTT, F.R.S. The Chairman said that before proceeding with the reading of the papers he would like to interpolate at this stage an exhibition of some slides by Dr. Alexander Scott, F. R. S., which would illustrate the linen used in the shroud of Tut-ankh-amen. Dr. Alexander Scott said that he had been invited by the President to exhibit some photographs of three specimens of linen cloths which were found in the tomb of King Tut-ankh-amen.This king died about I 350 B.c., therefore these specimens are almost 3300 years old. As they vary very notably in their state of preservation, colour and texture, it was thought that they might prove of interest to manufacturers of textiles at the present day. The photographs which were shown upon the screen were taken both by reflected and transmitted light so as to demonstrate the structure of each. The pictures here reproduced are all by reflected light (after bleaching when necessary) and are magnified fifteen times. From this the number of threads in each direction can easily be counted for each specimen. A represents the pall which was within the outermost shrine but covered the second shrine.I t is much coarser in texture than the other two and although very frail could be handled with care. I t was of a strong brown colour. (Fig. I..) B shows the structure of the cloth in which was wrapped a number of ceremonial staves found between the outer and the second shrines. I t was of a very dark brown colour and required handling with the utmost care, a great part having already gone to a fine powder. The feature here is the closeness of the texture and two threads going one way but only one the other. C was from the veil of filmy cloth which was thrown over the two pro- tecting goddesses who stood on guard at the entrance to the sepulchral chamber. I t was of a light brown, almost cream, colour and was comparatively strong notwithstanding its thinness and looseness of weaving.(Fig. 3.) (Fig. 2.)226 PROBLEMS RELATING TO TEXTILE FIBRES THE STRUCTURE OF LINEN CLOTH FOUND IN THE TOMB OF TUT-ANKH-AMEN. BY ALEXANDER SCOTT, F.R.S. The Chairman said that before proceeding with the reading of the papers he would like to interpolate at this stage an exhibition of some slides by Dr. Alexander Scott, F. R. S., which would illustrate the linen used in the shroud of Tut-ankh-amen. Dr. Alexander Scott said that he had been invited by the President to exhibit some photographs of three specimens of linen cloths which were found in the tomb of King Tut-ankh-amen. This king died about I 350 B.c., therefore these specimens are almost 3300 years old.As they vary very notably in their state of preservation, colour and texture, it was thought that they might prove of interest to manufacturers of textiles at the present day. The photographs which were shown upon the screen were taken both by reflected and transmitted light so as to demonstrate the structure of each. The pictures here reproduced are all by reflected light (after bleaching when necessary) and are magnified fifteen times. From this the number of threads in each direction can easily be counted for each specimen. A represents the pall which was within the outermost shrine but covered the second shrine. I t is much coarser in texture than the other two and although very frail could be handled with care. I t was of a strong brown colour. (Fig. I..) B shows the structure of the cloth in which was wrapped a number of ceremonial staves found between the outer and the second shrines. I t was of a very dark brown colour and required handling with the utmost care, a great part having already gone to a fine powder. The feature here is the closeness of the texture and two threads going one way but only one the other. C was from the veil of filmy cloth which was thrown over the two pro- tecting goddesses who stood on guard at the entrance to the sepulchral chamber. I t was of a light brown, almost cream, colour and was comparatively strong notwithstanding its thinness and looseness of weaving. (Fig. 3.) (Fig. 2.)

ISSN:0014-7672    

DOI:10.1039/TF9242000226

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. THE PHYSICAL PROPERTIES OF TEXTILE FIBRES I N RELA- TION TO TECHNICAL PROCESSES AND TO GENERAL COLLOID THEORY. B y S.A. SHORTER, D.Sc. (BRITISH RESEARCH ASSOCIATION FOR THE WOOLLEN AND WORSTED INDUSTRIES). Received May 16f4, 1924. CONTENTS. I. The Technically Important Properties of Fibres. 2. The Absorption of Water by Textile Fibres. 3. The Elastic Properties of Fibres. 4. The Finishing of Woollen and Worsted Fabrics. 5. A Theory of the Colloid Structure of Fibres. I. The Technically Important Properties of Fibres, In the course of their progress from the raw state to the finished fabric the different textile fibres go through a large variety of processes and their behaviour during these processes depends upon a correspondingly large number of factors. We can therefore consider the subject here in the crudest possible outline. Thus considered the processes of manufacture may be said to consist of (I) the formation of a coherent sliver from an ir- regular mass of fibres, (2) the thinning of this sliver (sometimes done in a large number of stages in the later of which twist is inserted) culminating in the process of spinning into yarn, (3) the weaving or knitting of this yarn into a fabric, (4) the ‘‘ finishing ” of this fabric, i.e.the conversion of the crude product of the loom into a saleable article. This outline is of course not true in its entirety of all cases of textile manufacture, but it fits the great majority of cases. The principal properties which govern the behaviour of fibres during the processes of manufacture may be classified under the following heads :- (I) The elastic properties (using the term in its widest sense, to relate to any kind of relation between deforming force and deformation). (2) The absorption of moisture and its effect on the elastic properties.(3) The surface structure of the fibre. The present address will be mainly concerned with (I) and (2). 2. The Absorption of Water by Textile Fibres. The absorption of water by textile fibres has been studied by a number of investigators 1 ~ 2 ~ f45. Though the work of Trouton and Pool indicated that the moisture content of wool is a function of the relative humidity only, the view put forward by Schloesing is generally accepted. Schloesing states that for a constant relative humidity the equilibrium regain decreases 228TEXTILE FIBRES AND COLLOID THEORY 229 with the temperature or, conversely, the atmospheric humidity necessary to produce a given moisture content increases with the temperature. As I pointed out some years ago t j this temperature effect is connected thermo- dynamically with the fact that the absorption of water is accompanied with the evolution of heat.I have recently used Schloesing’s data to calculate the heat of water absorption by means of the Kirchhoff equation 7 for the heat of dilution of a solution. The heat of absorption is very large when the fibre is dry, decreases as the moisture content of the fibre increases and approaches zero as the fibre approaches saturation.* There is a gradual change in the nature of the process of water absorption as the water content increases. The absorption of the first portions of water is the result of direct molecular attraction and takes place with a large evolution of heat.At this stage the vapour pressure of the water in the FIG. I. wool increases very slowly with the water content. The intensity of this attraction diminishes as the amount of water increases : the heat of absorp- tion diminishes and the vapour pressure begins to increase more rapidly. When the vapour pressure comes near to the saturation value the rate of increase diminishes more and more till the material becomes saturated. In the neighbourhood of saturation the process tends to resemble the osmotic absorption of water by a dilute solution-a process which, though it may require considerable force for its suppression, does not involve any appreciable evolution of heat.g The variation of the rate of evaporation with the moisture content1* and the volume changes which occur when water is absorbed 11* I* are also significant in connection with the change of the nature of the process of water absorption.230 PROPERTIES OF TEXTILE FIBRES I N RELATION TO The moisture content of textile fibres is of importance technically and commercially, in the first place because water forms a variable proportion of a commodity which is sold by weight (hence the need for standards of (( condition ”) and, secondly, because the water content exerts an influence on the behaviour of the material during processing and on the properties of the final product.3. The Elastic Properties of Fibres. The elastic properties of fibres and yarns have been studied by a number of investigators 131 14, 151 16* who all attribute the peculiarities in the elastic behaviour of fibres to plasticity, and speak of (‘ permanent strains ” in fibres.In a recent work17 I dispute this conclusion, and put forward the view that textile fibres are much more perfectly elastic than the results of these investigators would seem to indicate, and that the apparent elastic im- perfection is largely due (in the case of wool almost entirely due) to the fact that the elastic extension or contraction is impeded by a resistance of a viscous nature. Such viscous or plastic material as exists in a fibre is, so to speak, in parallel with the elastic material and does not interrupt its con- tinuity. A dynamical model which forms a first approximation to the elastic behaviour of a fibre is shown in Fig.I . I t consists of a spiral spring S attached to a piston working in a cylinder of viscous liquid. The cylinder is perforated with a fine capillary channel and connected to the bottom end of the cylinder with a second spring So (which is much more extensible than S). This system, which given sufficient time is a perfectly elastic system, owes the peculiarities of its elastic behaviour to the slowness with which the spring So tends to come into equilibrium with S. Thus if the system be loaded, unloaded and reloaded we get an extension-tension diagram of the type shown in Fig. 2. The curve starts out from the origin in the direction OK corresponding to the extensibility of S alone. The slope of the curve increases owing to the increasing rate of extension So.On un- loading we obtain the curve AB which at first has a very small slope owing to the fact that So continues to extend till the two springs come to the same tension. At this point the unloading curve is parallel to OK, and beyond it becomes steeper and steeper owing to the fact that So is con- tracting more and more quickly as the tension of S diminishes. On re- loading the contraction of So continues for a time (till the tensions equalise), so that the reloading curve CDE is initially at a small slope, becomes steeper and finally approaches to coincidence with the prolongation of the loading curve. The curves obtained by New l3 and Matthew l5 for cotton and linen yarns are very similar to Fig. 2. The general arrangement of loading, unloading and reloading curves is precisely the same.The only difference is that with the yarns the extensibility decreases as the load increases owing to a straightening of the fibres and a general initial tightening up of the yarn structure. In the work referred to above17 I show that the stress-strain diagrams of fibres and yarns may be explained in terms of the dynamical model. 3.n particular, the spring So corresponds to elastic elements which are held in a state of strain by the resistance of a surrounding viscous medium. In the absence of external forces such strains will be released at a rate dependent on the viscosity of this medium. If this viscosity is high we may get internal strains of great persistence.TECHNICAL PROCESSES AND TO COLLOID THEORY 231 By means of stress-strain (tension-extension) diagrams it is possible to study the relation between these internal strains and the external stretching force.Thus if a given force be applied rapidly and maintained for a lengthy period we get a rapid extension followed by a slow one. In the case of the model, the process of approach to equilibrium would be very simple-the rate of approach would be proportional to the distance from the equilibrium. With animal hairs (wool, human hair, etc.) no such simple law is obeyed. The process of extension proceeds for a very lengthy period -days or even weeks. The explanation of this is, not as might be supposed, that the elastic elements are showing a plastic yield, but that the fibre con- tains elastic elements with very different degrees of damping, so that on the first application of an external force the more lightly damped elements ex- c .- 4.a ii 4 C 0 E Tension FIQ.2. tend and, as time goes on, the extension of the more highly damped elements begins to show itself. We get a similar effect on removing the external force, and it is undoubtedly the extreme slowness of the recovery of the more highly damped elements that has given rise to the erroneous ideas of ‘‘ plasticity ” and “ permanent strains.” Similar considerations apply to the case where a fibre is held stretched to a definite length. We get an apparent elastic relaxation which, however, is very different from the effect contemplated in Maxwell’s theory of visc0sity.1~ I t is not the disappearance of a state of strain owing to molecular re-adjust- ment-it is merely the transference of a state of strain from lightly damped to highly damped e1ements.l 1 An important technical instance of this occurs when the “ shed ” of a loom is left open.232 PROPERTIES OF TEXTILE FIBRES I N RELATION TO Before going further into this theory we will consider the question of internal strains from the technical point of view.4. The Finishing of Woollen and Worsted Fabrics. The existence of latent strains in the wool fibre and the need for their elimination have been recognised in a vague way by the practical man for a long time. Many of the processes in cloth finishing are directly concerned with such strains. Greater definiteness was given to the theoretical basis of finishing by the work of Harrison,20 who showed (I) that wool fibres when dry (( exhibit a kind of plasticity in which the strains produced remain when the stress is removed but are accompanied by internal stresses,” (2) that such strains are released when the fibre is placed in cold water, (3) that wet fibres are truly elastic, (4) that in boiling water fibres are truly plastic.21 The fibres in a piece as it comes off the loom contain latent strains which are liable to be released when the cloth is wetted.These strains have been put in during carding, drawing, spinning, warping, etc. Any excessive tension, which according to earlier theories strains the fibre beyond its elastic limit, really results in the straining of highly damped elastic elements and therefore in latent strains of great persistence.To avoid the irregular shrinkage which might be caused by the release of such strains, the cloth is often crabbed or treated with boiling water while in the form of a tight roll. This eliminates these irregular strains by causing an internal readjustment, as in the annealing of steel or glass. The piece can now safely be washed in relatively cool water to get rid of oil and dirt. After washing the piece is fentered or dried in a stretched state. Since this drying is done at a temperature much below the boiling-point, the state of strain produced in tentering is not destroyed; it is merely rendered latent. This latent strain is largely eliminated by blowing (treat- ment with steam). To make certain that none of it is left in the cloth the process of London shnhking is sometimes carried out.This consists in wetting the cloth thoroughly and allowing it to dry-taking care to apply no more tension than is absolutely necessary. This process consists essen- tially of the release of latent strain (at this stage merely a uniform extension in length or width) which in the absence of external force disappears by the cloth shrinking. The finishing processes may therefore be said to involve (I) the action of cold water in releasing latent strain, ( 2 ) the action of boiling water or steam in destroying strain. 5. A Theory of the Colloid Structure of Fibres. In order to obtain a fibre structure which will reproduce in a general way the behaviour of the mechanical model shown in Fig. I we must suppose that the fibre consists of an elastic framework the interstices of which contain a viscous fluid.The divergences from a close quantitative correspondence with the model can be explained, as we have seen, by supposing that there are wide local variations in the viscosity of this fluid. The complete explanation of all the facts discussed in the preceding section is a very simple matter. All we have to do to explain the results (I), (2) and (3) of Harrison’ is to suppose that the viscous liquid which See the second paragraph of Section 4.TECHNICAL PROCESSES AND TO COLLOID THEORY 233 impedes the elastic framework is a gelatinous fluid whose impeding effect diminishes with increasing water content. To explain result (4) we must suppose that the elastic framework though unaffected by cold water has its elasticity impaired with boiling water, i.e.that it has an annealing tempera- ture of about rooo C. The rendering latent of strains by wetting, stretching, and drying stretched, such as occurs in tentering, consists in rendering mobile the gelatinous medium, stretching the framework, and rendering the medium viscous again by drying. The subsequent release of the strain by wetting again is, of course, due to the rendering mobile of the medium once more. To render the stretch permanent it would be necessary to attack the actual elastic framework with boiling water or steam. There is one experiment which illustrates the identity of the impeding action of the gelatinous medium with the viscosity of ordinary colloidal 0 Tension FIG.3. solutions. The resistance offered by the medium is diminished by exces- sive strain.22 This is shown by the difference between the tension-extension graph of a fibre the first time it is loaded and the second time. The first time the extensibility remains small up to quite high loads. The only extension which occurs is the small amount which can occur without shear of the viscous medium. Quite suddenly the resistance of the medium gives way and the extensibility increases very rapidly. If now the load be removed and, after a few minutes, reloading is commenced, the extensibility begins to increase at a smaller load than before, and in a much more gradual manner. The difference between the two graphs is illustrated in Fig. 3. This increased extensibility at low loads slowly diminishes, but the fibre takes a long time (several days) to get back to its original state.The theory is illustrated in a very perfect manner by wool and the animal hairs. In these the two portions are very clearly differentiated in properties. The elastic portion is very resistent, and the viscous portion234 PROPERTIES OF TEXTILE FIBRES IN RELATION TO very susceptible, to the action of water. Other fibres give similar stress- strain diagrams. Thus the types of diagram showing the instantaneous elastic yield and the slow yield and the corresponding recoveries may be obtained with the artificial silks, though in certain samples examined the elastic framework is attacked even by cold water, so that it is difficult to show the release of internal strains by wetting.This was tested in a new form of autographic machine 18 in which the effects of friction and inertia are reduced to a minimum so that the stress-strain relationships holding during rapid changes can be investigated. In this machine the recording pen is attached to the spring which measures the tension of the yarn, and records its vertical motion. The paper moves horizontally at a rate equal to that of the lower end of the yarn (the upper end of which is attached to the spring). I t will be readily seen that the machine gives a tension-extension diagram in which the extension axis is horizontal and the tension axis makes an angle of 45’ with the horizonal. Fig. 4a refers to a yarn which was stretched in the “dry” state (at about 7 per cent.regain). The carriage carrying the paper (and regulating the motion of the lower end of the yarn) was moved rapidly forward (A), a rest of a minute was made during which the yarn (which had extended In Fig. 4 are shown two graphs relating to a cotton yarn. FIG. 4.-1612’s Cotton Yarn. rather over 3 cm.) extended further. Other rests of a minute were made (B, C, D) and then the carriage was moved back till the tension became zero (E) with a residual (not permanent) strain of nearly 3 cm. A pause of one minute was made during which the yarn contracted and pulled the pen a short distance downwards. The tension was again adjusted to zero and another pause of one minute was made (F) during which the further contraction was barely perceptible. The carriage was then moved back to its starting place, the pen returning to 0, and the fibre hanging slack between the clamps.Next morning (about eighteen hours afterwards) the carriage was brought forward and then returned to its starting place, so that the pen described a small cycle (G) which indicated a residual extension of about 1-5 cm., and a recovery during the eighteen hours of nearly I cm. The yarn was then sprayed with water till it was thoroughly wet. I t was seen to tighten up between the clamps, and on describing a short cycle (H),. perfect recovery was indicated.“ The pen did not, of course, retrace its original path, as the extensibility of the wet yarn is much greater than that of the dry yarn. Other (unstretched) samples of the same yarn did not contract on wetting.TECHNICAL PROCESSES AND TO COLLOID THEORY 235 Fig. 4b relates to another sample of the same yarn which was soaked in water before testing. A pause of one minute was made at the end of the outward journey of the carriage (K). I t will be seen that the yarn is much more extensible. The residual extension was about I '4 cm. immedi- ately after unloading. This diminished to 0.3 cm. in about three minutes (L) and did not diminish any more even after several hours although the yarn was kept met. In this case therefore there seems to be a small permanent extension. REFERENCES. 1 Schloesing, Bul. SOC. Encour. Indust. Nat., 1893. 2 Hartshorne, Traits. of the Ntw England Cotton Manufac. Assn., September, 1905 ; 2 Trouton and Pool, Proc. Roy. SOC., An, p. 292, 1906. 4 Masson and Richards, Proc. Roy. SOC., A?8, p. 412, 1906. 5 Shorter and Hall, ?ow. Tex. Illst., June, 1924. 6 Shorter, Jour. SOC. Dyers and Col., December, 1920. TKirchhoff, Pogg. Ann., 103, p. 177, 1858. SShorter, YOUY. Tex. Inst., June, 1924. 'J Shorter, Jour. SOC. Dyers and Col., September, 1923. 10 Fisher, Proc. Roy. Soc., IO@, pp. 139 and 664, 1923. 11 H. R. Hirst, Publication No. 17, B.R.A.W.W.I. 12A. T. King, Publication No. 19, B.R.A.W.W.I. l3New, your. Tex. Inst., 1922, 13, p. 25. l4 Barratt, ibid., p. 45. l5 Matthew, ibid., p. 17. 16 Pierce, Jour. Tex. Inst., November, 1923. I7Shorter, Your Tex. Inst., 1924, 15, p. T207. 18 Shorter and Hall, Jour. Tex. Inst., 14, p. T493. l9 Maxwell, Phil. Trans., 156, p. 49, 1867. mHarrison, Proc. Roy. Soc., 94A, p. 460,1918. "See also Publication No. 12, B.R.A.W.W.I. !B Garrett, Dissertation, Heidelberg, 1903 ; see also Ostwald, Colloid Chemistry , April, 1911. p. 160.

ISSN:0014-7672    

DOI:10.1039/TF9242000228

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. MEASUREMENT OF THE TRANSPAKENCY OF A FABRIC. BY THOMAS BARRATT, DSc., F.INsT.P.(FROM THE T ~ A L BROADHURST LEE Co. LTD. RESEARCH LABORATORIES). Received May znd, 1924. I. Apparatus. The apparatus employed in these measurements consisted of a special form of Joly’s Photometer as described in another paper (“ Lustre produced in Cotton by Mercerisation,” Trans. Faraday Soc., this issue, Fig. 3, p. 242). For measurements of transparency, the fabrics were pinned over rectangular openings 0,, 0, in the sides of the blackened boxes containing the lamps L,, L,, and measurements made as described in the next section. 11. Transparency of Fabrics. (a) Tofad Tvaniparemy. The total transparency of a fabric is to be taken as the percentage of the incident light which is transmitted by the fabric. I t was measured as follows : A piece of fabric similar to that upon which measure- ments were to be made was pinned over aperture O,, in order to cut down the light to about the same intensity as that to be measured.The aperture 0, being uncovered, the neutral position of the photometer P was observed, FG being in line with EF. The fabric whose total transparency was required was then pinned over 0, and the neutral position again determined. From these two readings, and readings of the positions of the lamps L,, L2, the transparency of the fabric covering 02, i e . the percentage of incident light transmitted through it could be calculated at once. Example. Total Transparency of Fabric marked (( S.T.” ( I ) With fabric over 0, and aperture 0, uncovered, L,P = 30.1 ins. ; L,P = 10.4 ins. Taking the amount of light through 0, as unity, that from L2 is ( ~ o * I / I o * ~ ) ~ = 8-37 units.(2) With fabric ‘‘ S.T.” over 0 2 and the same fabric as before over 0,, L,P = 23-85 ins., LIP = 16-65 ins. The light through 0, is now (23*85/16*65)~= 2.06 units. This means that of 8-37 units of light through the uncovered aperture O,, only 2-06 units were transmitted by the fabric ‘‘ S.T.” Hence the Total Transparency of the Fabric was 8’3, = 0.246 or 2 -06 24-6 per cent. 236MEASUREMENT OF THE TRANSPARENCY OF A FABRIC 237 Fabric. Threads. The following results were obtained in this way (Table I.) :- Counts per inch. Transparency. TABLE I. Fabric “S.T. ” . . . Fabric ‘‘ D.T.” . . . Muslin . . . . Muslin hard finish . . Singles Voile . . . 110/120 I12 x I20 24‘6 per cent.50/50 93 x 104 15’5 19 IIO/IIO 86 x 86 37‘5 * 9 IIO/IIO 86 x 86 49’0 9 9 50/50 55 x 55 37’6 9 9 - .-r - FIG. I.-Photograph of muslin not treated for transparency effect. Magnification, 17 diameters. (6) Thread Transparency. The method outlined above gives the total transparency, ie. the total percentage of incident light transmitted by the threads and by the spaces between the threads. I t is important to measure separately the ‘‘ Thread Transparency,” or the percentage of the Z&ht facling on the threads aZone which is fransmitfed by them. A rough idea of thread transparency can be obtained with the aid of a microscope, or by photography. (Compare Figs. I and 2.) Exact measurements of this quantity were obtained with the photometer as follows :- Measurements having been made as above of the total transparency (24.6 per cent.) a piece of the same fabric (“S.T.”) was dyed black.The threads then allowed no light to penetrate them, while the spaces trans- mitted the same amount of light as before, the threads not being appreci- ably altered in section by dyeing. The photometer measurements then gave the transparency of the dyed fabric as 7.9 per cent. This means that the spaces alone transmitted 7.9 per cent. of the incident light, and that therefore the relative areas of the threads and spaces were as 92-1 to 7.9. The total transparency being 24-6 per cent., the light transmitted by the238 MEASUREMENT OF THE TRANSPARENCY OF A FABRIC Fabric. Threads. ,",:::::. ~_ 6'S.T." . . . IIO/IZO 112 x 120 Muslin . . .I I O ~ I I O 86 x 86 Muslin hard finish . IIO~IIO 86 x 86 Voile . . . threads alone was 24.6 - 7.9 = 16-7 per cent. of the light incident on both threads and spaces. Of this total light only 92.1 per cent. fell on the threads and 16.7 per cent. of this was transmitted. Hence the true thread transparency was 16*7/92*1 = 0.181 or 18.1 per cent. Generally, let S = the percentage of the total incident light through the spaces, and T, that through the threads. Then the percentage of in- cident light falling on the threads is IOO - s, and the percentage of this light transmitted by the threads, i.e. the thread transparency, is IOOT/(IOO - S). S 4 T T by subtraction. ~ ! . $ ~ ~ n ~ j 7.9 16'7 18.1 per cent. 37'5 16'95 20'55 24-8 ,, 4 9 0 1 26'4 22-6 30'8 ,, 41'7 25-25 16-45 22.1 ,.I FIG. a.-Photograph of muslin which has been treated to render it transparent. Magnification, 17 diameters. Comparison of Transjarenty and Thread Transparency of Two SimiZur Fabrics. There are at present on the market a number of fabrics which claim transparency as their principal asset. One of the most interesting appli- cations of the measurement of transparency is in the comparison of two similar fabrics, one of which has undergone treatment to render it trans- parent. The figures given in Table 11. include a " Muslin untreated '' andMEASUREMENT OF THE TRANSPARENCY OF A FABRIC 239 a “ Muslin, hard finish,” the latter having been treated by a trade finisher to increase its transparency. The measurements show that the treatment has increased the total transparency over 3 0 per cent. and the thread trans- parency by about 25 per cent. An increase in transparency is evident without any special apparatus. Photographs of the two fabrics are given in Figs. I and 2 with magnification about 1 7 diameters, and it is clear that the treated fabric will allow more light to Fenetrate it owing to the greater area of the spaces. Microscopic examination shows that the threads also have been rendered more transparent by the special treatment. This is shown to some extent in the photographs, where the treated threads appear lighter in comparison. My thanks are due to Messrs. Tootal Broadhurst Lee Co., Ltd. for permission to publish the above results, also to Miss M. Drury for useful hints in calculation of thread transparency, and to Dr. R. S. Willows for helpful advice during the experiments.

ISSN:0014-7672    

DOI:10.1039/TF9242000236

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No.13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. THE LUSTRE PRODUCED I N COTTON BY MERCERISATION.1 BY THOMAS BARRATT, D.Sc., F.INsT. P. (FROM THE TOOTAL BROADHURST LEE Co. LTD. RESEARCH LABORATORIES). Received May 2 4 1924. I. Introduction. I t would appear almost obvious that the brilliancy of a mercerised fabric must be due to the swelling up of the separate fibres, and the conse- quent more or less regular cylindrical shape that they assume.This would give a smooth surface in place of the well-known twisted, irregular shape of the unmercerised fibre, and the result would be a more regular reflection of the incident light. Lange takes this view, and remarks that the stretching of the fibres while still wet is a necessary part of the process, as fibres mer- cerised loose still retain many folds or creases. In confirmation of this he gives photographs which, however, according to Harrison do not prove the existence of these folds or creases. Fig. I shows a photograph of two cotton fibres, both of which were mercerised in NaOH 50’ Tw. in the cold, one being stretched during mercerisation, the other not. After washing and drying they were mounted on a slide and photographed.The unstretched fibre certainly shows folds and creases, which are not present in the stretched fibre, and it is very evident that the regularity of the latter would account for a large increase in the intensity of the light regularly reflected from it. When the fibres are again wetted and photographed while still wet (see Fig. 2) the creases to a large extent disappear. Huebner and Pope also disagree with Lange’s simple explanation, and attribute the lustre to the reflection of the light from spiral ridges still re- maining on the surfaces of the fibres after mercerisation. In illustration they give photographs of glass rods twisted to resemble the supposed shape of the mercerised fibres. Harrison (Zoc. cit.). disproves Huebner and Pope’s theory by showing that NaOH 50’ Tw.at goo C. produces more lustre in cotton than NaOH 35OTw. at zoo C. although the former shows a less number of spiral ridges. I t is difficult, moreover, to see how Huebner and Pope’s theory would apply to the explanation of the brilliant lustre observed in the cylindrical fibres of natural or artificial silk. Harrison also gives photographs of glass rods to illustrate certain points. I t may be noted here that photographs of glass rod models are often misleading unless the relative directions of incident light, glass rods, and axis of came a are also indicated. In Harrison’s photographs, for example, some of the glass rods 1 The experiments described in this papef were completed in 1921. ‘J.S.C.I., 23,410, 1904. 240 Fdrb. Zeit., p. 197, 1898.* Y.S.D.C., pp. 198-203, 1915.LUSTRE PRODUCED I N COTTON BY MERCERISATION 241 look bright and others dark simply, apparently because the angles between the rods and the direction of the incident light are different in the various cases. Incidentally Harrison appears to ray stress on the part played by internal reflection. He says : '' There is another point to be taken into ac- count, which is of even greater importance than the section, and that is the nature of the surfaces of the fibres, since this affects both internal and ex- ternal reJZTection.y' One would imagine that internal reflection, as far as lustre is concerned, might be ruled out of the question, for owing to the opaque nature of a dry cotton fibre there is very little chance of any great proportion of the light entering the fibre, and still less chance of much of it Fia.I. FIQ. 2. Cotton fibres, one mercerised under tension the other not. dry, Fig. 2 after wetting with water. Fig. I photographed coming out again after one or more internal reflections. I n any case it would be diffused and not regularly reflected. There is, however, a certain opalescent appearance in a mercerised fabric, which may possibly find its explanation in the dispersion of white light into its spectrum coours when internally reflected within a cylindrical semi-transparent body. Microscopic examination of a mercerised fibre, illuminated above by sunlight or a powerful artificial light, shows brilliant points of white light, and sometimes coloured light, produced by internal reflection (or possibly external re- fraction).Herzog asserts that the suitability of a particular cotton for the Chenz. Zeit., p. 1097, 1914.THE LUSTRE PRODUCED I N production of lustre on mercerisation can be gauged by microscopic exam- ination. The fibres are cut up into short lengths and placed on a slide in a drop of caustic soda solution of mercerking strength. The percentage of these which swell into a regular cylindrical shape then gives a rough quantitative measure of the lustre to be expected. The experiments described below were undertaken with the object of throwing light if possible on the cause of lustre, and of devising some kind of physical measurement of this interesting property. 11, Apparatus. For measurements of reflection of light from various surfaces, a special form of Joly’s photometer was designed, a plan of which is given in Fig.3. The fabrics, threads, or fibres to be examined were placed flat on the vertical surface S$,, whose front face was vertically over the hinge at F. This surface was movable about a horizontal or vertical axis, the amount of the movement being accurately measured by two brass circula? scales. The ‘SZ FIG. diagrammatic plan of photometer bench, the two arms EF, FG, being hinged at F. Lamp L,, L,, and photometer P, enclosed in black metal boxes, are movable along the graduated arms. The vertical surface S,S, can be rotated about hori- zontal or vertical axis, and the amount of this movement accurately measured. arm GF could be placed at any required angle with the arm EF.The surface S,S, could be removed when necessary. If required, the intensity ot the light from the lamps L,, L2 could be cut down by pinning waxed paper or a thin fabric over the openings 0,, 02. 111. Measurement of the Light Reflected or Scattered in Various Directions from Cotton Fibres, Threads, or Fabrics. In order to measure the percentage of incident light that was reflected or scattered from a given surface-say a fabric-the fabric was placed flat on the vertical dead-black surface S,S2. The arms of the bench, EF, FG, were fixed at any required angle, which was given by the horizontal circular scale. The lamp and photometer P being fixed in suitable positions, L, was moved until the neutral position of the photometer was found. The angles of incidence and reflection of the light were then read on the horizontal scale.The surface SIS, was then rotated round a vertical axis into a new position, and the readings repeated. Lastly the surface S,S2 was removed, L,, P, and L, placed in a straight line, and the neutral position again found.COTTON BY MERCERISATION 243 Examp Ze, Measurement of L&ht ReguZarly Reflected from Fabric A. Arms EF and FG were placed at angle 45'. A semi-transparent fabric was pinned over opening 0,. Angle GFS, = angle GFSo = 674". In neutral position LIP = 16.7 ins. ; L,P( = L2F + FP) = 18-3 ins. Thus the light from L, via F is (:$y = 1-20 times the light from L, (a); S,S2 was removed and L,, P, L2 placed in the same straight line. Then for the new neutral position, LIP I: 6.6 ins.; L2P = 18.3 ins., i.e.the light from L, is now (%! or 7-69 times that from L, (6). From (a) and (8) it is clear that the percentage of incident light which was reflected from the surface S,S2 was (1*20/7-69) x IOO or 15.6 per cent. The method above described was applied to the measurement of the light reflected or scattered at various angles from surfaces composed of (I) parallel fibres, (2) parallel threads, (3) fabrics. Angle between fibres and vertical. FIG. 4a.-Percentage of light regularly reflected from parallel fibres-I, glass ; 11, mer- cerised cotton ; 111, unmercerised cotton-as the fibres were rotated in their own plane. (I) Fibres.-Fibres of scoured Egyptian sliver were well combed, stretched as tightly as possible, and secured with cement across the hori- zontal diameters of four semicircular blackened metal frames 8 crns.long and 2 crns. wide. The frames were clamped side by side so that the fibres were in the same plane, and their lengths all in the same direction. After measurements of reflection had been made the fibres were mercerised under their own tension and the measurements repeated. Similar measurements were afterwards made on '' glass wool " fibres. ( 2 ) Threads.-Grey aeroplane yarn, mercerised and unmercerised, was wound round ffat black surfaces so that the threads, lying side by side, com- pletely covered the surface. (3) I;abrics.-The fabrics examined were (a) a special weave, (b) a sateen, both mercerised and unmercerised. The following experiments ((a), (b), and (6)) were carried out on all these surfaces :-244 THE LUSTRE PRODUCED IN (a) The surface was arranged so as to make the angle of incidence of the light on it equal to the angle of reflection, and the Reflecting Power " of the surhce measured with threads or fibres (I) vertical, (2) 45' to the vertical, (3) horizontal, the surface being rotated 45O at a time in its plane through 360".The results of the measurements in the case of the parallel fibres are given in Fig. 4a. They illustrate the fact that when the fibres are hori- zontal (with horizontal light) the intensity of the regularly reflected light is greatest for the glass fibres and least for the unmercerised cotton. The mercerised cotton, Zike the gZass, gives higher maxima and lower minima than the unmercerised cotton.(8) The threads ("floating threads" in the case of the sateen) or fibres being placed in a horizontal position on the vertical surface, so that " 10' 20' 30' 40' 5ff 60" 70' 80' 9(r 100' 110' 120. Angle 8 between incident light and plane of fibres. FIG. &-Percentage of light reflected from sateen, mercerised and unmercerised, as the angle of incidence of the light is varied. the light was incident on them parallel to their length, the surface S,S, was rotated about a vertical axis. This has the effect of altering the angle 6 (Fig. 3) so that the light entering the photometer from the surface is no longer that which is regularly reflected. As 6 is increased from I 0" to I 20° the amount of (diffused) light from the surface to the photometer first in- creases, reaches a maximum when angles of incidence and reflection are equal, and then decreases.The curves given in Fig. 4b illustrate these changes in the case of sateen and 4c brings out the differences between glass fibres and mercerised and unmercerised cotton fibres. Once more it is clear that the mercerised fibres act very much in the same way as the glass fibres.COTTON BY MERCERISATION 245 (c) Experiments similar to those of (6) were carried out with the threads or fibres always vertical, so that the light was incident on them at right- angles to their length. Fig. 4d shows the variation in the intensity of the reflected or scattered light as the surface is rotated. With horizontal light on vertical fibres, the distinction between mercerised and unmercerised cotton fibres and glass fibres is almost negligible.I t would appear therefore that most of the increased lustre shown in a mercerised fibre is due to the light which is regularly reflected in a direction along the length of the fibre. A numerical estimate of the lustre can be deduced from curves such as 4a and 46. Let D be the amount of light diffused in any direction and R that regu- larly reflected ; with a perfectly '' matt '' surface R will be zero and D will 0" Id lo' 30' 40' 50' So" 70' so' 90" 100' 110" 120" Angle 8 between incident light and plane of fibres. FIG. 4c.-Percentage of light reflected from fibres of glass and cotton for various angles The direction of the light was along the length of the of incidence of the light. fibres. be the same for all angles.Hence if we allow light to fall on a fabric at a given angle, measure the light at the angle of reflection and also at some other angle, the first quantity will be R + D and the other will be D, and it is the ratio of R to D that really determines the lustre. A measurement of the nature thus suggested can conveniently be made with the help of the curves given in Fig. 4c. These represent the variation in the percentage of light reflected from parallel fibres when the light remains incident alffays along the direction of the length of the fibres as the latter are rotated round a vertical axis. Regular reflection is measured at the apex of the curve, so that the height of the curve gives us a measure of R. The quantity D varies with the angle of incidence, but for convenience we can measure D246 THE LUSTRE PRODUCED IN at any convenient point, say where 8 (Fig. 4c) = 40" : (Regular reflection occurred when 8 = 67r).We thus obtain as a measure of the lustre, R/D :- Glass fibres . . . . 22-4 5'6 16.8 3'0 '* Mercerised". . . '' Unmercerised" . . . Of course the result is quite arbitrary, but it gives a strict basis of com- parison which in most cases is all that is required. 8 = angle between incident light and plane of fibres. FIG. @.-Percentage of light reflected from various fibres for different angles of inci- dence, the light being incident always perpendicular to the fibres. 1V. Photographic Illustrations. Many photographs were taken to illustrate the effects shown in the curves of Figs. 4a to 4d.Figs. 5 (a), (b), (c) are photographs of two sets of parallel fibres, one of which (the lower set) had been mercerised under tension, the other not. The fibres were placed in a horizontal position on a vertical surface, the light also being horizontal. I n Fig. 5 (a) angles of incidence and reflection were equal (6") ; in 5 (6) the angle of incidence was 12', reflection oo ; in 5 (c) incidence 48", reflection oo. I n 5 ( a ) the mercerised fibres appear brighter than the unmercerised, but in other positions the reverse is the case. Photo- graphs taken with horizontal light on vertical fibres showed little or no difference in the amounts of light reflected from mercerised and unmercerised fibres when angles of incidence and reflection were altered as before. This corresponds with the curves in Fig.4d. Similar results were obtained with single fibres as shown in Figs. 6a, 66 A few are given as examples. This agrees with the results shown in the curves of Fig. 4c.COTTON BY MERCERISATION 24 7 VOL. XX--T8--247248 THE LUSTRE PRODUCED IN and 7. I n all these photographs there are three sets of fibres, the four fibres in the middle being glass, the lower fibres mercerised cotton and the upper unmercerised cotton. I n 6a and 66 the fibres were mounted hori- zontally on a vertical surface, and horizontal light was employed. Angles of incidence and reflection were equal (6”) in 6 a ; in 6b these angles were 32’ and oo respectively. Fig. 7 is a photograph of the same fibres placed vertically with horizontal light, and under these conditions it was found as before that a change in the angles of incidence or reflection made no ap- preciable difference in the relative amounts of light from the three sets of fibres.In order further to explain these relative changes of brightness in the various fibres, photographs were taken of two glass rods of about 4 mm. diameter, one of the rods being truly cylindrical, while the other was given two or three twists to imitate the twists in an unmercerised cotton fibre. In Fig. 8 (a) and (6) the incident (horizontal) light was reflected from a hori-- zontal glass rod, (a) being regular reflection and (6) with angle of incidence 30°, and of reflection oo. The result corresponds with the effects illustrated in Figs. 46, 5a, b, c, and 6a, 6, for mercerised fibres, i.e.most of the reflected FIG. 7.-Same fibres as Figs. 6 (a) and 6 (b). Angles of incidence and reflection unequal. Light incident at right angles to fibres. light is contained in a very narrow angle, the scattering being very small. I n a letter to Nature, Nov. 17th, 1921, p. 369, J. H. Shaxby shows that a very bright ring or b‘ halo ” of light is caused by the reflection of light in- cident along the length of a smooth cylinder. “The reflected light is practically a right cone with its axis along that of the cylinder.” Fig. 8c gives a photograph of the same glass rod placed vertically. I n this position very little variation of the light was observed as angles of incidence and reflection were altered. The same thing has already been noticed in t h e case of cotton or glass fibres placed vertically in horizontal light. Fig.8dis a photograph of the twisted glass rod, intended to imitate an unmercerised fibre. There is a certain amount of light reflected at all angles as in the case of unmercerised fibres. V. Remarks and Conclusions. The photographs and curves illustrating the experiments described above bring out very clearly the fact that the light reflected from a mercer- ised fibre in certain positions is concentrated within a small angle. In theCOTTON BY MERCERISATION 249 case of the unmercerised twisted fibre the reflected light is scattered, or spread out in a wider angle. The lustre is intensified when a number of mercerised fibres are placed parallel with each other. Hence the en- hanced effect in a sateen with “ floating threads.” There seems to be littJe doubt that the lustre can be accounted for by a single surface reflection.Internal reflection may produce an “opal- escent ” effect by acting in a similar way to that of small drops of water in the formation of the rainbow, but will not have much influence on true 1 us t re. ( c ) (4 FIG. &-Glass rod 4 mm. diameter. (a) and ( b ) light incident along rod ; (c) perpen- dicular to length of rod; (CZ) reflected light from twisted glass rod. Perhaps the twisted glass rods in Huebner and Pope’s and Harrison’s ex- periments appeared to imitate lustre in a fabric because of the bright points of light that were shown. These points of light in a fabric, however, are due to the interlacing of the fibres amongst one another in the fabric, and not to the twist in them. I t is to this distribution of the points of high light- which can be seen separately in a low-power lens-that some lustrous cotton fabrics owe their beauty ; a sheet of light such as is shown in an artificial silk fabric or a calendered fabric is not nearly so beautiful.250 LUSTRE PRODUCED IN COTTON BY MERCERISATION L L Schreinering ” gives beauty similarly because of its small regular ridges. A careful examination of a well-mercerised cotton fabric will show a distribution of very bright and very dull points, the total amount of re- flected light being usually rather less than from the more uniformly lighted surface of an unmercerised fabric. This latter fact is due to the greater transparency of the mercerised fabric and the consequent loss of reflected light. The transparency of a fabric may be increased by 30 per cent. or more by mercerising it under tension, and reference to such curves as 4b and 4c will show that the total amount of light reflectedfrom the mercerised cloth is less than that from the unmercerised. I t is only within a small cone, as shown by the sharp peak of the curves referred to, that the mer- cerised fibres reflect more light than the unmercerised, and it is due to the contrast effect illustrated by the shape of these curves that a mercerised fabric owes its lustre. The experiments described were done in 1921 in the Physical Laboratories of Messrs. Tootal Broadhurst, Lee & Co., Ltd.-to whom my thanks are due for permission to publish. I am also greatly indebted to Dr. R S. Willows for his most valuable advice and help.

ISSN:0014-7672    

DOI:10.1039/TF9242000240

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE. BY C. R. NODDER, M.A. (THE LINEN INDUSTRY RESEARCH ASSOCI-4TION) Received May I 6th, I g 2 4.The structural and optical characters of the flax fibre, and of so-called bast fibres in general, have attracted the attention of numerous investigators from the time of Nageli’s pioneer work ( I 862) down to the present day. The present state of our knowledge in this field has recently been thoroughly reviewed by Keimers,l who gives a very useful list of references to the literature. Zsigmondy, in his (‘ Kolloidchemie,” and Freundlich, in his ‘( Capillarchemie,” 3 refer in some detail to cellulose fibres as examples of colloid gels. The bast fibres, of which flax may be taken as typical, are very noteworthy examples of structures which combine crystalline and colloid properties. I t is the purpose of this paper to review briefly the more important considerations which have led to the recognition of this double r81e and, further, to discuss in some detail a number of observations of characters of the flax fibre-mainly structural-which are of interest on account of their possible physico-chemical relationships.Such a review seems very desirable at the present time, since references to the subject in English literature are very scanty; much of the work has appeared in continental publications which are not readily accessible, for example, the paper by Reimers referred to above. Little need be said regarding the general colloid properties of cellulose fibres, as these are now well recognised. These properties are manifested in the sorptive power of the fibres, their swelling behaviour in water and in various aqueous solutions and in the undoubted colloid properties of solutions of cellulose and its derivatives.The point of fundamental importance is the recognition of the cellulose fibre as a two-phase system in which the cellulose particles collectively present a very large surface. An insight into the form and arrangement of the cellulose particles may be obtained by microscopic examination of fibres which have been suitably treated. Thus when a flax or ramie fibre is mounted in water or other suitable medium and vigorously compressed beneath the coverslip (e.g. with the tip of a scapel) innumerable fissures become evident and the fibre-wall 1 H. Reimers, ‘‘ Die, Verschiedenheiten im strukturellen Aufbau der Bastfasern. 23rd edition, 1920. See also ‘‘ Report of Discussions on Colloids,” Trans.Faraday 32nd edition, 1922. Mitt. Deut. Forschungs-Instituts f. Textilstoffe in Karlsruhe,” 1920-21, pp. 109-282. SOL, 1921, PSI. 251252 SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE becomes divided into extremely fine fibrils, spirally arranged.’ It is often possible by compressing the fibre to a sufficient extent to bring about such a subdivision of the fabrils that they pass beyond the limits of microscopic visibility. There can be little doubt of the close relationship between these visible fibrils and the colloid particles of the cellulose gel. The optical be- haviour of the fibrils and of the fibre-walls as a whole show them, as we shall see, to be essentially crystalline. Nageli’s conception of the structure of vegetable membranes was remarkably near the truth ; he recognised, indeed, the crystalline character of the sub-microscopic particles, to which he gave the name micelles.” Stmcture.-The structure of the fibre will now be considered in some detail as a necessary preliminary to a description of its optical behaviour.The fibre is not homogeneous, but shows several layers which differ in their properties. In cross-sections of typical flax fibre-bundles the true middle- lamella is seen between the fibres as a very delicate membrane, somewhat thickened at the corners, which stains deeply with ruthenium red and appears uniformly dark between crossed nicols. Within the middle-lamella, and forming the outermost layer of the fibre itself, is the thin “primary layer ’’ which is distinguishable according to Reimers-who agrees with Dippel and other earlier workers-by the fact that it appears bright when thin cross-sections are examined between crossed nicols ; it is stated that, on account of a Brewster-cross effect, actually only those parts of the fibre- sections which are in the diagonal setting appear bright.In the case of flax this primary layer is very thin and not readily discernible, but a thin outer layer of the fibre, diKering in properties from the inner layers, may be distinguighed in another way which I. believe has not been previously described. Within the primary layer are the ‘‘ secondary layers ’’ which in strictly transverse sections do not transmit much light between crossed nicols. Although a definite Brewster-cross effect is not readily seen in transverse sections of the flax fibre, it is probable that in common with bast fibres in which a Brewster cross is observedY3 flax has the radial structure to which this effect is due.This is a matter, however, which calls for further careful investigation. Reimers describes hemp as showing imperfect crosses. Nageli and Schwendener (1877) described the production of the Brewster cross by sections of the tracheids of Pinus. I t may not be generally known that flax fibres transmit light very readily in the longitudinal direction, so that the fibres appear bright in cross-sections of the stem as much as half-an-inch in thickness. This is especially striking after the section has been treated with caustic soda solution, when the fibres appear bright yellow.Care- ful observation of thick sections stained with ruthenium red illuminated by both reflected and transmitted light shows that a thin outer layer of the fibre wall, adjoining the rniddle-lamella, does not transmit light in a longi- tudinal direction nearly so readily as the interior layers, so that it appears opaque in sections of +-inch or less in thickness. This difference is pre- sumably to be referred to a difference in the orientation of the micelles in This is referred to below. 1 X rough idea of the fineness of the fibrils is given by the illustration of a compressed ramie fibre in 7. Text Inst., 1922, 170, Fig. 16. For making evident fibrils of the greatest possible fineness a strong solution of calcium chloride tinted with iodine seems most suitable as the mounting medium in which the fibre is compressed.”ee Reimers, loc. cit., p. 119, Dippel, L., 1869, ‘L Das Mikroskop u. seine Anwen- dung” (Braunschweig), 2 Teil, pp. 129, 310, 322. .i E.K. willow, see Reimers, Loc. cif., p. 209.SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE 253 the outer layer, a suggestion which appears to be in agreement with differences which have been recorded in the form and orientation of the optical indicatrix in the primary and secondary layers of various fibres.l The (‘ beading ” effect often observable when flax fibres are swollen by the viscose method,2 is apparently due to the lesser power of swelling possessed b y the “ primary layer ” of the cell-wall and the irregular folds which were described as sometimes visible in the wall of compressed flax fibres are probably in this layer.The number of secondary layers which may be clearly distinguished in cross-sections of flax fibres which have not been specially treated is rarely more than ten and is usually less.* I n fibres viewed longitudinally, Q number of layers may often be distinguished in optical section and give to the fibre a longitudinally striated appearance. Fibres compressed beneath the coverslip as described above show these layers more distinctly, but it has only been possible to distinguish clearly some twelve or fifteen layers in fibres thus treated. Searle,5 however, has recently shown that in cross-sections swollen with 15 per cent. caustic soda solution and compressed beneath the coverslip it is possible to distinguish quite a large number of layers (about 50).The picture which one has formed, therefore, of the flax fibre is that it is built up of numerous layers, each with a spiro-fibrillar structure. Before the optical properties of the fibre are described it will be advis- able to consider more fully the nature of the spiral arrangement of the fibrils. Flax fibres which have not been subjected to a special compression treatment often show fine, more or less longitudinal, fissures in the cell- wall.6 I t is easy to show, by compressing the fibre beneath the cover-slip, that these fissures follow the trend of the fibrils. Observation of the slope of the fissures in the untreated fibres leads to the conclusion that the fibrils run, on an average, at an angle of about IO’, or rather more, to the axis of the fibre.In fibres which have been moderately compressed beneath the cover-slip it may readily be seen that the fibrils in the outer secondary layers run in left-handed spirals-the spirals of an ordinary wood-screw being considered as right-handed. The fibrils of the inner layers have been described as sometimes running in right-handed spirals. I t is not unlikely that observers have been deceived in this connection by an optical effect (Welcker’s effect). If the microscope is slowly racked down when an object possessing very fine fissures is under observation it is seen that the first image of a fissure is a dark line-it being assumed that the object is mounted in a medium of lower refractive index. When the microscope is focussed a little lower the image of the same fissure is a bright line.When a flax fibre with walls of a suitable thickness is under examination the appearance of internal spirals with opposite twist may be produced as follows : as the microscope is racked down the dark images of the fissures on the upper half of the fibre are first seen ; at a slightly lower focus the dark images of the fissures on the lower half of the fibre come into view ; then follow the bright images of fissures on the upper and lower half of the fibre respectively. Since the possibility of deception by Welcker’s effect 1 E g . Reimers, Zoc. cit., p. 193. 3r. Text. Inst., 1922, p. 164, Fig. 5. 4 We may note here that the secondary layers show differences in that they stain increasingly more deeply with ruthenium red as the lumen is approached ; the outer layers show very little affinity for this stain.Linen Industry Reseach Association, Memoir No. 20 (1924). 1.e. in the secondary layers which form the bulk of the fibre-wall. the primary wall of flax fibres has not been satisfactorily determined. See, for example, Searle, Zoc. cit. The structure of VOL. XX-T9254 SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE has been realised a considerable number of flax fibres have been examined but in no case was the presence of right-handed internal spirals discernible, even in the broad fibres from the base of the stem. If they really occur, the cell-wall layers with a right-handed spiral structure are probably always relatively thin, and possibly of rare occurrence ; certainly the characteristic- anti-clockwise drying twist of flax seems never to be disturbed.Double Refractz’on.-Flax fibres are strongly double refracting, sur- passing in this respect the micas among minerals, so that interference colours up to a green of the second order are observed between crossed nicols. In longitudinal view the fibre as a whole shows straight extinc- tion ; but this behaviour appears to be due to the combined action of the upper and lower halves of the fibre as it lies on the stage of the microscope, i.e. due to a compensating action of the fibrils in the upper and lower halves, since they lie inclined in opposite directions with respect to the axis of the fibre. Thus, if a fibre is compressed in the manner described above it is possible to separate the fibrils to such an extent that in places they are not crossed by fibrils running in a different direction.The fibrils, or groups of fibrils, are then themselves seen to show straight extinction between crossed nicols. The observations of Balls (Zoc. lit.,. p. 77) appear to show that in the cotton hair the extinction of the fibrils IS oblique, When flax fibres are swollen with caustic soda solution and compressed it is found that the separate fibrils or groups (bands) of fibrils still show double refraction (first order grey) and straight extincti0n.l The existence of double-refraction in the fibrils themselves, even when swollen, seems fairly good evidence that the double refraction of the fibre is not due to internal tensions.Further and more convincing evidence is given by Searle (hc. cit.) who shows that the minute fragments produced by the breakdown of tendered flax fibres are doubly refracting. The optical behaviour of the fibre is thus seen to suggest very strongly that we are dealing with a crystal, or more correctly, a crystalline aggregate, since thin transverse sections of the bast-fibres in general give rise to a Brewster-cross effect. It is not difficult to determine the optical sign of the fibre-walls and the character of the indicatrix. Measurements of the refractive indices have been made by various observers. Herzog2 gives figures obtained by an immersion method. The mean refractive index is about 1.56 at zoo C. for sodium light and lies therefore between that of Canada balsam and that of aniline.On account of the double refraction of the fibre no liquid medium can be found in which its outlines are invisible in unpolarised light.3 Herzog’s results show that the specific birefringence is as high as 0.067.~ The use of a selenite plate shows that additive colours are obtained when the principal axis of the plate is parallel to the length of the fibre- or, where isolated portions of the cell-wall are being examined, parallel to the fibrils-and, sitice the small amount of light transmitted by cross- 1See Fig. 14, 7. Text Ivtst., 1922, p. 169. J Herzog, A., g b Llchtbrechung u. Mikrophotographie von Faserstoffen, Mitt. Fors- chungs-Instituts, Sorau,” 1920~21. 4 See also Remec, B., ‘‘ U ber die spezifische Doppelbrechung der Pflanzenfasern.Sitzungsberichte der Kais. Akadamie der Wissensch. in Wien, Mathem. naturw. Klasse,” 1901. Bd. 60, Abt. I, 364-87 ; Korn, R., b b Unterscheidung einiger Fasern, insbes- ondere der Leinen- u. Hanf-hser, Jahresb. d. Verein f. angew. bot.,” 1909, Bd. 7, 189 ; Dissertation Berlin, 1916, and Ambronn, Herm., ‘‘ Ueber eine neue Methode z. Best- immung der Brechungs-exponenten anisotropischer mikroskopischer Objekte. Ber. d, mathem. physik. Klasse d., Kgl. Sachs. Ges. d. Wissensch. zu Leipzig,” 1893. Herzog, A., ‘‘ Textile Forschung,” 1922, No. 2, p. 58.SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE 255 sections of the fibre between crossed nicols indicates that there is no great difference between the refractive indices a and fl, it is concluded that the fibrils or crystallites composing the fibre-walls are optically positive, i.e., light travels with the lowest velocity in the fibre when its vibrations are parallel to the fibrils. The use of a selenite plate in connection with cross-sections of the fibre shows that the shortest axis of the indicatrix is radial.The longest axis is parallel to the fibrils and the inteimediate axis lies tangen- tially and at right angles to the fibrils. These relationships of the indicatrix, which are generally true for the secondary layers of bast fibres, were first made clear by Dippel (Zoc. cit., 1 8 6 9 , ~ ~ . 318). Nageli and Schwendenerl obtained similar results from an exaniination of the tracheids of Pinus. It has been shown in the case of ramie that when the fibres are nitrated the optical sign becomes negative.When the cellulose is regenerated, by the use of ammonium sulphide, the fibres become again positive. This behaviour would seem to offer a further argument against the view that the double refraction of the fibre may be due to internal strains. The nitrated fibre may be regarded as a pseudomorph after cellulose. PZeochroism.-Flax fibres when stained with methylene blue, congo red, safranine and many other dyes show very pronounced pleochroi~m,~ with strong absorption of light when the axis of the fibre is parallel to the vibra- tion plane of the polariser. Fibres stained with iodine show a pleochroism almost as pronounced as that of biotite as seen in rock-sections. This behaviour lends some support to the view that the fibre is a crystalline aggregate; it is probably due to the oriented arrangement of the coloured particles, although according to Zsigmondy the arrangement of the particles at different distances apart in different directions is an alternative explana- tion of such an effect. Ambronn has shown that all the substances examined which confer pleochroism on the fibre are themselves pleochroic.* Of interest in this connection are the results obtained by Gaubert who shows, for example, that phthalic acid crystals coloured with methylene blue are pleochroic.X-ray S)kctrog7aphic Experimnts.-Further evidence of the crystalline nature of the cellulose in the flax fibre is obtained by the application of the method of Debye and Scherrer.g Herzog and Jancke have obtained point-diagrams with flax and ramie fibres in parallel arrangement which they consider show clearly their crystalline structure, with a rhombic (or possibly monoclinic) symmetry for the component crystallites. With powdered fibres Debye-Scherrer rings are obtained, the character of which points to similar conclusions.Herzog and Londberg have recently shown that when cellulose fibres are nitrated and then denitrated the regenerated cellulose has the same X-ray spectrographic characters as the original fibres, i.e., the chemical reactions have not disturbed the orientation of the cellu- lose particles. The conception of the flax fibre as a concentrically lamellated spiro- fibrillar crystalline aggregate with colloidal properties is closely similar to 1 Nageli, C., and Schwendener, S., “ Das Mikroskop,” 2nd edition, 1877, Leipzig.2 Hans Ambronn, Koll. Zeitschr., 1916, IS, 80, 273. 3 Ambronn, Herm., I‘ Pleochroismus, Ber. d. D. Bot. Ges.,” 1888; A m . Phy~., 1888,3+ 341 ; 1889,38, 160. 4 Zslgmondy makes frequent references to Ambronn’s work in his Kolloidckemie, 3rd edition. Gaubert, P., I@-10, e.g., C.r., 1909, 149, 10004-106. Phys. ZEit., 19x7, 18, 291. 7 Ber. d. D. Cli. Gss., 1920, 53, 2162. Be*., 1924, 57, p. 329.256 SOME STKUCTURA4L CHARACTERS OF THE FLAX FIBRE Balls’ conception of the cotton hair. With such a conception in mind we may now pass on to consider some further characters of the fibre. Dislocation Marks (Verschiebungen).-Now that the essentially crystal- line nature of the fibre is, as I. believe, fully established there seems to be little difficulty in accepting the view that these transverse markings of the fibre are due to a twinning similar to that produced in minerals by pressure (e.g., calcite, carnallite, mica). When the fibre is in a position of extinction between crossed nicols the dislocation marks appear bright.The be- haviour of a fibre when it is rotated between crossed nicols suggests that the dislocation marks have themselves straight extinction, although they rarely appear quite dark. The transverse markings often give rise to a cross-like appearance in the fibre. In such cases careful focussing shows we are dealing with a dislocation in the upper side of the fibre overlying a dislocation in the lower part of the fibre. The markings are in fact always approximately at right-angles to the trend of the fibrils.In consequence of this, hemp fibres, in which the fibrils run in right-handed spirals, may be distinguished from flax by a careful examination of the dislocation marks. Searle has recently shown that the transverse marking are of considerable practical importance in that they are points of weakness in the fibre. Ex- cessive mechanical treatment of flax (e.g., in scutching) is found to produce large numbers of dislocation marks and the fibre is at the same time weakened. The cause of this weakness is probably the minute fissuring, or local lateral separation of the fibrils, in the neighbourhood of a dislocation mark. This fissuring is, moreover, probably the cause of the more intense staining of the dislocation marks that is obtained with iodine solution and other reagent^,^ and as Searle points out here also the fibre is most susceptible of attack by hydrolytic and oxidising agents.I t has been pointed out that the transverse markings of the cotton hair also are often accompanied by fissures which give rise to the appearance of rows of pores (de Mosenthal’s ‘‘ Stomata ”). There is clearly a close resemblance between the transverse markings of the cotton hair and those of the flax fibre. Balls7 and Denham * have recorded similar conclusions regarding the nature of the transverse markings of the cotton hair and (Denham) of de Mosenthal’s (‘ Stomata.” Transverse markings are often extremely numerous in fibres taken from a bleached fabric. Careful observation usually reveals the presence of numerous fine markings which at first pass unnoticed. Pre- sumably all these markings are due to mechanical forces imposed on the fibres during the various processes which the fabric undergoes.Searle shows that fibres tendered by over-bleaching develop ‘‘ planes of segmentation ” See also Ambronn, Ztschr. f. wissensch. Mikroskokie, 1918, 32, 9, 32, or Zsig- Reimers, H., Textilberichte, 1921, p. 381 ; Herzog, A., Mitt. Forschungs. Institiits. mondy, Kolloidchernie, 3rd Edn., 1920, p. 112. Sorau, 1920-21, p. 41 ; Nodder, C. R., y. Text. Inst., 1922, 215. 3 Linen Industry Research Assn., Memoir No. 20, rgnq. Miiller, W., Faserforschung, 1921, Vol. I., No. I, p. I (‘‘ EinAuss und Erkennung mechanischer Behandlung der Flacnsfaser ”).Herzog, A., Mitt. Forschzrngs. Instituts. Sorau, 1920-21, p. 40 (*‘ Ueber die Ursachen des Stumpfwerdens der Flachsfaser bei der Kiinstlichen Trocknung des Rostflachses ”) ; Nodder, C. R., J. Text. Itrst., 1922, No 10, p. 215. I believe Herzog was the first to point out the true nature of de Mosenthal’s 64 Stomata ”-Herzog, A., Knnststofe, I, 1911,425 (‘* Uber das mikroskopische Verhalten der Baumwolle in Kupferoxydammoniak ”). When my observations were published (y. Text. Inst., 1922, p. 213)~ I was not aware of the existence of Herzog’s paper. 7 Balls, L., Proc. Roy. SOC., 1923-24, Series B, 95, p. 72. a3!. Text. Inst., 1923, 14, T . 85.SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE 257 at the transverse marks when swollen with caustic soda solution and gently pressed beneath the cover-slip ; at the same time the fibre-wall breaks down in a direction parallel to the trend of the fibrils, so that numerous short rod-like fragments are produced.He shows, further, that fibres tendered by different agencies show considerable variation in behaviour when sub- mitted to a similar treatment. Thus fibres tendered by the action of micro-organisms do not show the numerous ‘L planes of segmentation ” characteristic of over-bleached fibres. If it is conceded that the transverse markings are especially liable to chemical attack their presence in the fibre is of interest with reference to the surprising differences in the viscosities of solutions of cellulose which are brought about by such apparently gentle treatments of the fibre as a boil in weak sodium carbonate solution.I t is conceivable that extremely numerous sub-microscopic dislocations are present in the fibre and form preferential points of attack of chemical reagents, and that when the cellu- lose is dissolved the fibrils break transversely at the attacked points. The shorter length of the fibrils in a solution obtained from more heavily at- tacked fibres would afford a possible explanation of its lower viscosity. Twisting Behaviuur.-As we have seen, flax and hemp fibres differ in that the fibrils composing the secondary layers run in left- and right-handed spirals respectively. The fact that the drying twist of the fibres is in op- posite directions is closely related to this structural difference.’ The twist- ing behaviour appears to be explicable on the assumption that there is a differential contraction or elongation of the fibrils in different layers of the cell-wall.When a fibre is treated with caustic soda solution, say of 40° Tw., there is a considerable contraction in length and a twisting movement in the direction which one would twist the fibre if an attempt were made to untwist the fibrils (as one would untwist the fibres in a yarn). If a short piece of a fibre (say I mm. long) is treated with caustic soda solution the appearance produced suggests that the outer layers contract more than the inner layers since the cut ends become convex.2 I t seems probable, therefore, that the ‘‘ untwisting ” behaviour on mercerising, or wetting (which also produces a small contraction in fibre length), is due to the greater contraction of the fibrils in the outer secondary layers of the cell-wall,3 the fibre acting as a multiple Breguet spiral with very high pitch.Since on wetting with water the contraction in fibre-length is very small (possibly niZ if the fibre is under a small tension) whereas the untwisting is very vigorous, it would appear that in this case the contraction is practically confined to the outer layers. SweZZing-It is not proposed to deal with the swelling properties of the fibre in detail on this occasion. We may note, however, that fibres are in general found to swell to the greatest extent in the direction of the shortest axis of the optical indicatrix, i.e., radially. If an ellipsoid is constructed to represent the swelling properties of the fibre it is found to bear a re- ciprocal relationship to the optical indi~atrix.~ In a general way this be- 1 If a wet flax fibre is held at one end and allowed to dry, the free end (held towards one) is seen to move in a clockwise direction.The difference in twisting behaviour of flax and hemp was apparently first described by Sonntag (Ber. d. D. Bot. Ges., 1911, 3, 2 Cf. Fig. 15 ; y. Text. Imt., 1922, p. 216. 3 The primary layer, of flax especially, is considered too thin to have an appreciable 4 Schwendener, S., ‘‘ Ueber Quellung u. Doppelbrechung vegetabilischer Membranen. 669). influence in this respect. Sitzungsb. d. Kgl. Akad. der Wissensch. zu Berlin,” 1887, 659-702.258 SOME STRUCTURAL CHARACTERS OF THE FLAX FIBRE haviour may be explicable as the result of the forcing apart of the ultimate fibrils or micelles of the fibre by the absorbed liquid.The contraction of the fibre in length in caustic soda solutions may in part be similarly explicable, as may be seen from the behaviour of wire-models made to illustrate the spiro- fibrillar structure of the fibre. In connection with the action of caustic soda solutions on bast fibres one or two points of interest may be noted. I t has been shown that 10 per cent. solutions produce a remarkably well- defined maximum contraction in single flax and ramie fibres (under a very small tension). There appears to be no sharp change in any physical property of caustic solutions at this strength ; the effect is probably closely related to changes in the degree of hydration of the sodium ion. There is, further, a pronounced flattening of the concentration-contraction curve with solutions containing about 15 per cent. of caustic soda, i.e., solutions with maximum specific conductivity for electricity. It is of interest to note that Collins and Williams in a recent paper record a maximum swelling of cotton hairs with solutions of caustic soda and caustic potash of maximum specific electrical conductivity. An outstanding question of great interest is the cause of the spiral ar- rangement of the fibrils and of the opposite direction of the twist in differ- ent fibres. I t is not yet clear whether the protoplast has the determining influence in this respect or whether the stereochemical properties of the cellulose play a part. Since the structure of the fibres is clearly related to the mechanical needs of the plant it might be argued that the pitch and direction of the spirals is determined by the activities of the protoplast, but such a (teleological) argument will not find favour with the majority of biologists nowadays. In hemp fibres the slope of the fibrils with respect to the long axis of the fibre is very small-about go-and this appears to supply an argument in favour of the view that the protoplast has the determining action; such a slope seems too small to be accounted for by a definite stereochemical property of the cellulose. Nodder, C. R., and Kinkead, R. W., y. Text. Iust., 1923, p. T 133. ". Text. Inst., 1924, T 154.

ISSN:0014-7672    

DOI:10.1039/TF9242000251

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No.13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. PROPERTIES OF THE SILK FIBRE. BY WILLIAM S. DENHAM, D.Sc., F.I.C., AND THOMAS LONSDALE, M.Sc., A.INsT.P. (BRITISH SILK RESEARCH ASSOCIATION). Received May I 5 fh, I g 24. The continuous thread or bave with which the silkworm constructs its cocoon is composed of two parallel filaments or bnkq of the silk proper or fibroin, which are cemented together and surrounded by the silk gum or sericin. The gum can be removed from the fibroin by the action of soap solution and in other ways, and when this is done the individual ultimate filaments can be separated; but as the silk is not usually “degummed” until several cocoon threads or baves have been united to form a com- posite thread, the brins that were partners in the original bave remain associated in fabrics woven from yam formed from the continuous filaments.In spun silk which is produced from degummed waste silk by spinning processes similar to those employed in spinning cotton, wool or linen, the filaments are in lengths of a few centimetres and the brins originally partnered need no longer be associated. Ordinary silk is derived from the mulberry silkworm (Bombyx mori) of which there are various cultivated races ; other species of silkworms, which yield Tussah, Shantung and wild silk generally, are not usually cultivated. I t is mulberry fibroin, or de- gummed silk derived from Bombyx mori the properties of which (chiefly physical) are now described and the “fibre” specially considered is the ultimate filament of fibroin two of which are already present in the cocoon thread. The elementary composition of fibroin may be expressed by the empirical formula C1,H,,N,O, ; that of sericin by the empirical formula C15H,,N,0, ; other formulae have been proposed.Of the amino acids present in the product obtained by the hydrolytic degradation of mulberry fibroin, glycine, alanine and tyrosine occur in the greatest proportion ; various polypeptides and related substances have been obtained by the regulated hydrolysis of fibroin.2 Eonnation.-According to the researches of Le Blanc3 the fibroin (or fibroinogen) is secreted mainly in the convoluted posterior portion of the silk organ where it appears as particles which fuse gradually to a viscous mass.This passes to the reservoir where the sericin first appears. Le Blanc found no sericin-secreting gland and, modifying Bolley’s notion that Composifion.-Both fibroin and sericin are proteins. 1 Mulder, Bers. ’jfahresb., 17, 380. a Fischer, Abderhalden and others ; numerous publications in the “ Zeitschrift fur 3 ‘L Reports of the Laboratoire d’Etudes de la Soie,” Lyon, 1887-1888. physiologische Chemie,” xgo1-1g24. 259260 PROPERTIES OF THE SILK FIBRE the sericin is formed by oxidation of the fibroin when the thread emerges into the atmosphere (4 the above empirical formulae), he suggests that oxidation of the external layers of fibroin with formation G f sericin may occur within the reservoir which is in communication with the outside air by means of numerous tubes.The silk material (which receives additions of other material) passes to the excretory canal at the termination of which the two sections of the silk-organ (which is duplicated) come together at the spinneret where the envelopes of sericin fuse, and the double thread or bave is formed; when the thread emerges into the open air the fibroin solidifies almost instantaneously, the sericin more slowly. Dz'mensions.-The continuous thread emitted by the silkworm may be 1200 to 1500 metres long. The degummed single filaments are not of uniform thickness throughout ; constrictions and small swellings occur here and there, and the irregularities are more pronounced in the thread from the inner layers of the cocoon next the chrysalis, and in the thread from the outer layer, than in the middle portion which can be reeled.Observed longitudinally under the microscope the brin presents the appear- ance of a smooth transparent cylindrical filament, sometimes slightly flattened ; faintly marked longitudinal striations may be observed with a magnification of 600 diam. The cross-section is usually triangular with rounded angles and straight or curved sides. Among the recorded measurements of the diameter of the ultimate filament of mulberry silk are those by Wiener and Prasch,' v. Hohnel,2 Hanau~ck,~ Wardle,4 S01aro.~ Great variations in the measured diameter may occur in a given sample of silk and the variations are greater if the diameters of the samples of silk of different origin are compared. measured the diameter of each of the brins constituting the bave at points 50 metres apart in the reelable silk from several races of silkworm.He found that:- ( I ) The diameter of the brin is least at the two extremities of the reel- able silk. (2) The two brins of the same bave are of different diameters, and the difference between the two brins is not the same throughout the whole length of the reelable bave. (3) The difference between the diameters of the two brins is greatest at the beginning and end of the bave; in the interval it is small and may even vanish. The following measurements by Solaro of the diameter of the ultimate filament of mulberry silk (origin not stated) are quoted because they illus- trate the difference of thickness of the cross-section of the fibre in different directions :- Wardle Maximum Minimum Diameter.Diameter. Observed longitudinally 0~00180 cm. o*ooog cm. Cross-section Longer axis '00227 cm. *00136 cm. Shorter axis -00185 cm. sooog cm. 1 Dingier's Poiytechn. yourn., 1868, 190, 123 and 233. (' Die Mikroskopie der technisch-verwendeten Faserstoffe," p. 214. '6 Microscopy of Technical Products," tr. by Winton, p. 147. Rondot, " L'Art de la Soie," II., 273 ; yawn. SOC. Arts, 1884-1885, 669. 5 6 ' Studio Microscopic0 e Chimico, etc. LOC. cit. Loc. cit.PROPERTIES OF THE SILK FIBRE 261 The diameter of the filaments is different in different media; for the same sample of Indian mulberry silk prepared for spinning, the means of 2 0 0 measurements of the diameter were ,001 19 cm.in air ; and -001 32 cm. in water (B. S. R. A,). Dens@.-The density of silk fibroin has been determined by Robinet, Persoz, Vignon, Chardonnet and Levrat whose work is recorded in full or quoted in the reports for 1889-1890, 1891 and 1906 to 1907 of the ‘‘ Laboratoire d’Etudes de la Soie,” Lyon. Kobinet using c r k de liiorence (silkworm gut) with the object of avoiding errors due to air-cavities found the value 1-367 ; Persoz found 1.357 in water; Vignon (for French silk) 0.887 in mercury, and I -34 in benzene ; Chardonnet 1.43 in an aqueous solution of cadmium borotungstate. The most trustworthy determinations appear to be those made by Levrat with a modified form of Regnault’s voluminometer ; he found values ranging from I -40 to I -45 for dry fibroin from different races of the mulberry silkworm.Structure of the Tilament.-The longitudinal striae which may be observed with a magnification of 500-600 diameters in the degummed filament are regarded as altogether superficial by Le Blancl who considers the filament to be completely homogeneous. Other authors, however, regard these striae as indications of a fibrillar structure for the existence of which in the thicker filaments of wild silks there is a considerable amount of evidence. A parallel structure of the filaments both of mulberry and wild silks is indicated by their ultramicroscopic photographs and the breakdown of the mulberry filament into fibrillae can certainly be induced by the action of chemical reagents such as acids and alkalies, or mechani- cally; irregularities in dyeing and the faults in silk fabrics sometimes called “ mildew ” are ascribed to this splitting of the filament.A mono- graph “Sullo sfilacciarsi delle Sete Tinte ” issued in 1905 by the Societa Anomina co-operativa per la Stagionatura e 1’Assagio delle Sete, ed Affini of Milan, which contains a discussion of this question with citation of the relative literature has been published in English translation together with an account of Wardle’s researches on the divisibility of the silk filament. X-Ray Strzcctllre.-R. 0. Herzog and Jancke* examined silk by the Debye-Scherrer powder method and faund indications of a crystalline structure. Double Refraction.-The colours shown by different kinds of silk when viewed between crossed nicols are said to be useful in their identificati~n.~ Harrison attributes the double refraction exhibited by silk filaments to internal strains produced during the extension of the filament and rendered permanent by its setting; the interior portions seem to be in a state of radial compression.Refruche Index.-A. Herzog gives the refractive index of natural silk as 1.567. Lustre.-If a number of filaments are arranged parallel to each other in the form of a flat smooth ribbon the intensity of the light reflected from the surface so formed can be measured. 1 L O C . c i t . 3 Heywood, Manchester, 190s. 4Zeitschrift f f i r Physik., 3, 196, 343, 1920. ti Silbermann, “ Die Seide,” VoI. II., 169 ; A.Herzog, loc. cit. A. Herzog, ‘‘ Unterscheidung der naturlichen und kunstlichen Seiden.” See also Brill, Ann. dcr Chemie, 434, p. 204. Proc. Roy. SOC., A 94. 7 Lci. c i f .262 PROPERTIES OF THE SILK FIBRE Observer. If such a surface 0 is illuminated by a beam of light 10, then some of the light is specularly reflected from the surface in the direction OS, such that 01 and 0 s make equal angles with the normal, and some is reflected diffusely from the surface and interior of the material in any direction such as OD. I t is supposed that the observed lustre of a textile material is connected with its power of reflecting specularly a fraction of the incident light. Thus Adderley 1 measures the brightness of a thick ribbon of cotton fibres in the direction OS, the plane 10s being perpendicular to the length of the fibres.He calls this brightness, which is due both to specularly and diffusely reflected light, the (( lustre ” of the material. ‘* Lustre ” of Fil. Perp. to Plane 10s ‘’ Lustre ” of Fil. Parll. to Plane 10s’ I I 0 FIG. I. Zart by a modification of the Ostwald half-shade photometer measures the brightness (S) in the direction 0 s and the brightness (D) in another direction OD and expresses them in terms of the brightness of a standard surface of barium sulphate which is illuminated by incident light of the same intensity as that illuminating the textile material; he calls (S-D) the (‘ lustre ” of the material, D being termed the “ covering power.” Again, Schultz by means of an instrument of the same essential nature S measures the brightness in the directions 0 s and OD and calk the ratio - D the ‘‘ lustre ” of the material.A considerable difference is found in the ‘‘ lustre ” of filaments according as the length of the filaments is in the plane 10s or perpendicular to it. The following table shows the results obtained by different observers for ribbons of filaments of different materials. TABLE I. Material. Viscose Silk A. . 9 , c. * R a l Silk Viscose Silk (i) : ,, ’ 9 (2) * I I Zart 1 Scilltz B.S.R.A. ’ 9 70 ‘87 ‘32 ‘60 ‘5 7 Definition of ‘’ Lustre ” Used. Zart’s Schultz’s Adderley ’s ’ 9 1’ An agreement upon the definition of lustre would be useful. The expression employed by Zart, but foreshadowed by Blonde1 and used by numerous writers to express the amount of “gloss ” on papers, etc., appears ~oztmal of the Textile Institute, April, 1924.‘‘ Melliand’s Textilberichte,” Vol. V., 1924. See ‘‘ Krais, Technische Fortschritteberichte,” Vol. HI., p. 13 ct seq. 2 ‘‘ Melliand’s Textilberichte,” Vol. IV., No. III., 1923. 4 ‘‘ La Luniihe Electrique,” Vol. XXXV., p. 615, circu 1892.PROPERTIES OF THE SILK FIBRE 263 to be the best of those just enumerated. I t assumes, hawever, that the surface is matt (apparent brightness the same when viewed at any angle) except at the angle of specular reflection when light specularly reflected is added to this uniform apparent brightness ; work in progress at the B.S.R.A. indicates that this assumption requires examination. Adderley's expression, although it has the merit of simplicity might, it would seem, give a con- siderable degree of lustre, for matt surfaces not usually regarded as lustrous, and Schultz's expression might represent a lustrous black surface as pos- sessing an abnormally high degree of lustre owing to the small magnitude of the diffusely reflected light.Hy~~oosco~ic Properties.-T. Schloesing states that the quantity of water contained by silk and other textile materials when in hygroscopic equili- brium with the surrounding air is a function both of the relative humidity and theatemperatwe ; Trouton and Pool on the other hand conclude both from their experimental results (with flannel) and from thermodynamical considerations, that within the usual atmospheric ranges the amount of water held by the material is a function of the relative humidity only, a conclusion verified experimentally by Masson and Richards for ~ o t t o n .~ In agreement with the observation of Masson and Richards* that the apparently constant value for the moisture content of cotton which is absorbing moisture in an atmosphere of definite humidity differs from the apparently constant value for the moisture content of cotton which is losing moisture in the same atmosphere, and with the similar observation made by Hartshorne 5 on wool, it is found (B.S.R.A.) that silk shows a like behaviour. Mention may be made also of an apparent dependence of the rate of regain on the temperature at which the silk is dried. gives figures for bundles of silk filaments which indicate that for increasing humidity the breaking load decreases slightly, this decrease being accompanied by a slight increase in the extension at break.Imbibih'on.-The swelling of fibroin in water is indicated by the increase in diameter of the filaments when placed in water, which has already been mentioned; swelling occurs in other liquids also, for example, in benzine. The heat of imbibition of air dried fibroin in aqueous solutions of acids and alkalies has been measured by V i g n ~ n . ~ Solubility in Wafer.-Distilled water has very little solvent action on fibroin. IOO cubic centirnetres of distilled water after 24 hours contact with 0.5 gram of fibroin at 18" C. were found to have dissolved from o to 0.04 per cent. of the fibroin as determined from the amount of nitrogen that passed into solution; at 5o°C.the amount of fibroin dissolved by distilled water is not much greater ; but at I O O O C . about 9-5 per cent. was found to be dissolved irom 0.5 gram of fibroin by distilled water in three hours (B.S.R.A.). Action ~f An2 and AZKaZine SoZufions.-Determinations of the amount of fibroin dissolved by acids and alkalies in dilute aqueous solution indicate a dependence of the solvent action on the hydrion concentration of the solution. Rise of temperature greatly accelerates the action of dilute solutions of acids and alkalies on fibroin which is quickly dissolved in the cold by concentrated solutions of these reagents. Wilkomm C.R., 106,808. T . Amer. SOC. Mech. EnK., 1917, 3, 1073. Leipzig, '' Monatschr. fur Textilind," 1909. Bull. SOC. Chim., 1890, 3.2 PPOC. Roy. SOC., A. 77, 292. 4 L O C . cit. a Proc. Roy. SOC., A. 79, 412.PROPERTIES OF THE SILK FIBRE Degummed Silk unspecified ,, Italian Silk, dry ,, Italian Silk, wet 1-27 den. The treatment of silk with solutions of mineral acids or of formic acid may cause it to contract.’ The presence in silk of a small proportion of acid induces or increases the peculiar crunching sound made by silk when it is crushed in the hand known as ‘‘ scroop ” with which a characteristic (‘ handle ” is associated. Isoelectric Point.-Regarding fibroin as, like other proteins, amphoteric in character, its absorption of acids and bases from their solutions and, secondarily perhaps, the amount of fibroin dissolved by these solutions, may be ascribed to salt formation. The action both of acids and alkalis on fibroin is least when the concentration of these reagents approaches zero ; it increases rapidly with increasing concentration on the alkaline side of the neutral point, more slowly on the acid side.I t is thus indicated that the isoelectric point of fibroin, like that of other proteins, lies on the acid side of the neutral point, a conclusion verified by its more precise experimental determination. The hydrion concentration at the isoelectric point of fibroin is expressed by a pH value of about 3-8 (B.S.R.A.). Solvents f o r Fib-oin other than Acids and AlkaZis.-The following reagents dissolve fibroin : aqueous cuprammonium hydroxide ; aqueous nickel-ammonium hydroxide ; aqueous basic zinc chloride ; and alkaline solution of copper hydroxide in water containing glycerine.6 The cupram- monium solution gives a flocculent precipitate with weak acids, but not after standing since the fibroin appears to be quickly hydrolysed (B.S.R.A.).Elastic Properfies and Tensile Sfrength of the Silk Pilamenf.-Measure- ments of the breaking load and elongation at break of the bave such as those recorded in the report of the Lyons Lab~ratory,~ in the reports of the Milan Laboratory,s and by Wardle,g are not of immediate concern in a discussion of the properties of the ultimate filaments of silk, nor are the results of technical tests which are usually performed on raw silk or other composite silk threads. The elastic properties of silk are dependent on its source and history ; the filaments moreover have varying diameters, and are troublesome to handle-some may be extended beyond the elastic limit by a load of 0.5 gram.The investigation of the elastic properties of these filaments requires therefore the expenditure both of skill and time, reasons no doubt for the small amount of information that exists concerning them. The following observations may be quoted (Table 11.) :- TABLE 11. BREAKING LOAD AND EXTENSION AT BREAK OF SILK (ULTIMATE FILAMENT). 4-01 16.7 T. Barratt,r. T. Inst. 1922, 17. 14.3 Forschungs Inst. f. 17.3 Textil Industrie; quoted by 7’8 7.3 Krais, Textil Industrie, p. 12.. Breaking Extension Per Cent. Description. pal, I at Break, I Observer, etc. I I I 1 Depoully, J.S.D.C. 1899, 8 ; Farrell, J.S.D.C., 1905, 70 ; Sansone, Rev. Gett. Mat. Col., 1911, 194.2 Mills and Takamine, CAem. SOC. Trans., 1883, 141 ; Knecht, J.S.D.C. 1888, 104 ; Vignon, C. R., rrg,613,121, 916 ; Walker and Appleyard, Cherrt. SOC. Trans., 1896,1334. 3 Ozanam, C.R., 55, 833. Richardson, r. SOC. Chem. Ind.. 1893,426. 5Persoz, C.R., 1862, 810, 848. Loewe, Chem. Centralbl., 1877, 11. 7 Report of the Lyons Laboratory, 4, 149; 8, 141. * Reports of the Milan Laboratory, 1594-1899, I 17. 9 r. SOC. of Arts, 33, p. 669.PROPERTIES OF THE SILK FIBRE 265 The results in Table III. were obtained with a simple form of extenso- meter to be described in a later publication. The extensions of individual ultimate filaments were observed at loads increasing by increments of about 0.2 gram ; but the results in the table include only the extensions and loads at the elastic limit (as deduced from a curve) and at break, I t should be noted that the silk had already undergone the industrial operation of reeling from the cocoon.I t is not claimed that the very close agreement of the means in Columns IV. and V. of the two sections of the Table is other than fortuitous. On the assumption that the cross-section of the filaments is circular the tensile strength of this Chinese silk is calculated to be about 3-3 x 109 dynes per sq. cm.; that of the Italian silk quoted by Krais (Table 11.) to be 3.9 x 109 dynes per sq. cm. The filaments are often, however, more nearly triangular than circular in cross-section and these calculated values of the tensile strength are therefore on the low side. FIG. 2. If the simple assumption could be made that each filament of Table 111.had a uniform diameter throughout its length one would expect to find greater regularities in the differences between the individual filaments than actually occur. Nevertheless the figures indicate an elastic extension and an extension beyond the elastic limit, more clearly displayed in Fig. 2 which shows the load-extension curves for filaments 16, 24 and 25 of Table 111. which have widely different breaking loads. If, as suggested above, the diameter of each filament is not uniform throughout its length, the extensions per unit length will be less than those of a uniform filament which shows an equal breaking load; because the thicker portions will not be fully extended by a load sufficient to break the thinner portions.Fig. 2 contains also a composite curve for several filaments which had about the same breaking weights and extensions at break. The curves indicate that the load-extension curve beyond the elastic limit is approximately linear. The area under the load-extension curve taken up to the breaking-point is a measure of the work done per initial266 PROPERTIES OF THE SILK FIBRE TABLE 111. 43 DETERMINATIONS OF THE EXTENSION AND LOAD AT THE ELASTIC LIMIT AND AT BREAK OF INDIVIDUAL ULTIMATE FILAMENTS (CHINA FILATURE, 14/16 DEN., DE- GUMMED) OF MEAN DIAMETBR 0~00117 mm. RELATIVB HUMIDITY 58-66 PER CENT. No. I 2 3 4 5 6 7 8 9 I0 I1 I2 I3 I4 15 16 I7 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 I. %x? 5'9 5 '9 6.0 5'9 6.0 5 '9 5 '9 6'0 5'9 6 '0 6*1 5 '9 6.0 5'9 5'9 6 '0 5 '9 6.0 6'0 6'0 6.0 6'0 5 '9 5'9 5 '9 Means 4 '2 4'2 4'1 4 '2 4'0 4'1 4'1 4 '2 4 '0 4'0 4'0 4 '0 4 '2 4'2 4'0 4 '2 4'2 4 '2 11.111. At Elastic Limit. Load, Grns. 1 '3 1 '3 1'0 '9 1'0 I '0 -8 '8 08 '7 -6 '9 -8 '5 '7 '9 08 '7 *8 '7 '5 1'0 1'0 I 'I -6 '85 1.0 1'2 '9 '7 '9 '9 *8 '8 '8 1.0 '9 1'0 1'1 1'2 '9 1 '5 '7 1'0 Extension Per Cent. 2'2 1'7 2 '3 2'3 1 '9 2'5 1.7 1'7 1'7 2'0 2'0 1'0 2'0 1 '7 1 '5 1'9 2'2 I '2 1 '4 1.7 1.5 2.5 2'5 I -8 I '2 1.85 1'4 1'4 1'4 2'3 1 '7 1 '4 3'0 3'0 -8 3 '5 2-6 2.4 5'0 3'8 2'9 2'2 2'0 2'1 IV. V. At Break Breaking Load, Gms. 4'9 4'6 4'6 4'4 4'3 4'2 4'2 4'2 4'2 4'2 4'0 4'0 3'9 3 *8 3'7 3'6 3'6 3'5 3'2 2-6 2.5 2'4 2'4 2'2 2'0 3'65 5 '5 5'0 4'7 4'4 4'3 4-0 4'0 3'8 3'6 3 '5 3 '5 3'4 3'3 3'1 3'0 2'7 1.9 1.7 Extension Per Cent.17'3 19'5 14.2 I 6.0 18-2 17-8 16.0 15.0 15-0 14% 24'5 18.7 20.3 18.2 16.3 25.0 16'0 14.0 17.0 12.7 15'3 19.3 8.0 13 '0 12'0 16.6 21'0 13'8 23.2 18'6 19'5 20'0 17'8 12.9 19.0 18.0 8.0 16.8 16.0 22.8 17'5 10.5 9'0 12'0 VI. K. -61 -60 -62 '59 '59 '57 -56 '59 '5 9 '59 -56 '5 7 -56 -6 I '57 '59 '5 9 -58 '57 '56 -58 '5 7 -62 '64 -61 '59 '63 -60 '5 9 '5 7 -60 -60 '55 -58 '5 4 5 8 '5 7 '54 -60 '5 7 '5 7 '64 -60 .60 Means 2.3 8 3'63 16.5 '5 9PROPERTIES OF THE SILK FIBRE 267 unit length in breaking the filament ; the curve has been drawn and this area measured for each filament broken and a factor K calculated such that work done extension at break x breaking load' This factor is shown in Table 111. (col. VI.). The mean value of the work done in breaking one filament per initial unit length = W = 0.37 gram cm.units. Measurements made on longer filaments for convenience of observation have shown that if a filament is strained beyond the elastic limit, a rapid initial recovery occurs when the load is removed followed by a more gradual recovery, but a permanent set of some magnitude may occur. Assuming the cross-section of the filaments to be circular we obtain a value for Young's Modulus of 0.4 x 10ll dynes per sq. cm. Speczfic Heat.-The values of the specific heat given below are for raw silk. Testenoirel found 0.35 calories per gram, using benzene as the calorimetric fluid ; Kinoshita using an ice-calorimeter found 0.32 calories per gram ; Dietz gives the value 0.33 calories per gram.ThmzaZ Cunductivify.-The thermal conductivities of silk and other textile materials have been investigated by Musselt and by Grober with reference to the lagging properties of these materials ; and by Miss Rood with reference to clothing. Miss Rood infers that at equal density the thermal conductivities increase in the order silk, wool, artificial silk, linen, cotton. EZectricad 1muZahbn.-Notwithstanding the extensive use of silk for electrical insulation exact data regarding the electrical properties of silk do not appear to be available. We&hting.-Degummed silk retains tenaciously a small proportion of oil or fat even after repeated extractions with ~olvents.~ The loading of silk with organic substances such as sugar, mentioned in technical hand- books, is possibly no longer very prevalent.The absorption of tannin by silk, a property which has long been utilised in dyeing silk black, has been studied by Heermann who considers it to be similar to the absorption of tannin by hide. More important technically, is the property possessed by fibroin of ab- sorbing inorganic substances notably compounds of tin a property some- times utilised for the weighting of certain classes of goods. In the technical process of tin-weighting the silk is soaked in a solution of stannic chloride and is then centrifuged and washed with water ; the tin hydroxide present in the silk is now fixed by treatment with a solution of sodium phosphate (Na,HP04) and subsequent washing with water. By a repetition of these processes a large proportion of tin compounds can be introduced into the silk which receives a final treatment with a solution of sodium silicate sometimes preceded by treatment with a solution of aluminium sulphate.Many theories or variants of the same theory have been proposed to K - 1 Reports of the Lyons Laboratory, 9,59. 2 Gesundheits-Irrg., 1916,3? 497-503. 3 Leipzig, Motratsch. f. Texttltnd, 1912. 4Zeitsch. V ~ Y . deutsch. Ittg., 1908, 906 and 1003. 13 Phys. Review, 1921, 356. 7 B.S.R.A. ; cf. also Mudge, Anterican Silk, J., 1921, p. 65, on the extraction of oil 8 Favber-Ztg., 1908, 4. Ibid., 1910 and 1911, 49, 13x9. from thrown silk.268 PROPERTIES OF THE SILK FIBRE explain the mechanism of the tin-weighting process, a summary of which is given by Heermann.l The facts appear to be these :- The silk absorbs or combines with the tin and chlorine in the proportion in which the elements are present in stannic chloride ; the stannic chloride is hydrolysed in the subsequent washing process with formation of stannic hydroxide which remains in the silk and of hydrochloric acid which is re- moved by the wash water ; the silk absorbs sodium phosphate (Na2HP04) as a whole from the phosphate bath, and alkali is removed when the silk is washed with water after the phosphate bath.2 Heermann has made an extensive comparative study of the mordant- ing (weighting) of silk by compounds of tin, iron, chromium, and aluminium ; the results with the different mordants are on the whole similar.Were it not for this fact and for the figures given by Ristenpart 4 for the tin-weight- ing of cotton and viscose and other kinds of artificial silk the chemical theory of tin-weighting proposed by Fichter and Miiller which is based on experimental facts would appear to be satisfactory.According to these authors the amino acids form compounds with stannic chloride ; thus alanine and stannic chloride give the compound SnCI, . 4 . CH, . CH(NH,) . COOH, which is completely hydrolysed by water with regeneration of alanine and separation of a transparent colourless jelly of stannic acid. Fichter and Muller show that fibroin reacts with stannic chloride in the presence of benzene with the formation of a similar compound to those formed from the amino acids. They consider that the weighting process consists in the formition of such a compound, and its decomposition by hydro- lysis during washing with regeneration of the fibroin which is thus ready to go through the cycle again. The stannic acid is precipitated in the fibre as a colourless gelatinous deposit which forms an adsorption compound with sodium phosphate. The ash of weighted silk retains the form of the filaments and this pseudomorphous ash is hardly to be distinguished under the niicroscope from the original filaments. The diameters of the filaments increase when silk is weighted, and according to Heermann any contraction in length is slight. Weighted silk has lost little in strength but the extension at break becomes less as the amount of weighting increase^.^ Weighted silk deteriorates more quickly under the action of light and other agencies than unweighted silk.s I t is remarkable that the original properties of the silk are restored when the weighting is removed by the action of acids.g Dyeing.-Silk is dyed readily by acid, basic and direct cotton colours. Mordant colours are also employed ; the use of sulphur and vat dyes is now extending, protective materials being employed against the action of the alkaline liquors. 1 Mitt. Konigliches Materialprtifurtgsamt, 3, 446 (1915). 2 Heermann, Parber-Ztg., numerous papers chiefly rgo3-1go5 ; Ristenpart, Firrber- 3 Lac. crt. 7 Gnehm and Banziger, Fdrbsr-Ztg., 1857, I ; Sisley, Rev. Gen. Mat. Col., 1909, 33. 8 Sisley, loc. cit. Ztg., 1909, 232, 250. 4 LOC. cit. Fdrber-Ztg., 1915, 253. Ibid., 1907, 113. Ristenpart, Fdrber-Ztg., 1907, 273.

ISSN:0014-7672    

DOI:10.1039/TF9242000259

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. GENERAL DISCUSSION. Chairman :- J. H. Lester, M. Sc. The Chairman, representing the Textile Institute, opened the General Discussion on the preceding group of papers, which dealt for the most part with the physical properties of the various textile 6 bres. Mr. Lester said he would like to emphasise what Dr. Balls had said in his encouragement of the physicist to take up the problems of the textile industries. Undoubtedly there was an enormous ground to be covered and in the past this had, unfortunately, been taken up and dealt with, so far as it had gone, either by the chemist or by that person in the works who deals with the testing of yarns and who has been known as the tester.The work of this man was, in a sense, fundamental work on which textile physical investigations must proceed, but such men were, as a rule, badly trained either in chemistry or physics, and very often there was no training in physics at all. There was no doubt, therefore, that the greatest and most far-reaching results would be achieved by the application of physical science to the textile industries. He would also like to add a word about research. People in the industry came to him every day asking, in essence, ‘‘ What is research? ” I t was a very elementary thing but surely it was for the physicist, the chemist, and for those who had some scientific training, to show to those people in the industry, in the language of the industry, what research is and what it may mean to the industry.It had been said-and there was some truth in it-that the industry must learn the language of science. There was, however, a common language, the English language, in which scientific ideas might be expressed and it was up to the Research Associations, in particular, and to those who claimed a knowledge of science in general, so to express themselves as to obtain the real working interest and assistance of those engaged in the industry. No one knew that better than those engaged in Research Association work, and this was an aspect of the subject which, he hoped, would receive the very serious consideration of those who were trying to apply science to these industries. Mr. H. J. Poole said he would like to refer to the results of some experiments on the elastic properties of gelatin which were in almost direct parallel with those described by Dr.Shorter and which led to practically the same conclusions. They were of interest as showing a connection between what is obviously a colloidal system and the textile fibres under consideration. When sticks of gelatin jelly are loaded an immediate ex- tension occurs, followed by a slow movement which, according to the conditions of loading, either slackens off uniformly to zero or continues in- 269PROBLEMS RELATING TO TEXTILE FIBRES definitely. form illustrated (Fig. I). The curve connecting the extension and time is of the general I n the case of a structure such as Dr. Shorter postulates the extension should be connected with the time and the load by a formula such as :- dE L = KIE - KS 2dT where E is the extension at any one instant, and Kl and K2 are constants.L is the applied load, The constant Kl involves the modulus of elasticity and K2 is pro- portional both to the viscosity of the liquid and to some power of the dispersion of the gel. 'l'his equation is linear in E and ~ and the slope of the derived curve is inversely proportional to the viscosity when the elasticity and dispersion remain constant. By plotting values of the extension and the rate of extension this hypothesis can be tested. In all the experiments he had carried out on gelatin a curve was obtained which is strictly linear down to a point and then shows an inflexion into a curved path (Fig. 2). If the duration of the experiment is so adjusted that the load is released before this inflexion point is reached, the extension is found to be exactly reversible, but if the inflexion point is passed then a permanent set is induced whose amount is equal to the excess allowed.That these effects are not accidental is shown by several facts, the most important of which are the independence of the slope of the derived curves to the applied load, and the fact that the time taken to reach the inflexion point is also independent of the load. dE d TDISCUSSION 2 7 1 This differentiation of the phenomenon of creep into a viscous reversible flow and an irreversible deformation had led him to a slightly different conclusion from that of Dr. Shorter, viz., that in the case of gelatin, at any rate, the solid or fibrillary struc- ture which is indicated (and confirmed by other experiments) is capable of permanent deformation due either to a plastic yield or to fibrils slipping over one another.In the case of gelatin it has not been found neces- sary to postulate zones of liquid of varying viscosity. This was, however, t it- ? in no sense a criticism of Dr. Shorter’s deductions but a necessarily sketchy description of a parallel in an un- doubtedly colloidal system. He hoped shortly to publish a detailed account of these experiments. Dr. W. H. J. Mardles said that the elastic behaviour just described is common to many materials other than textile fibres, e.g. glass and mild stee1,l cellulose acetate.2 The molecular orientation theory might be a possible alternative to the theory which had been put forward by Dr. Shorter, for with time, whilst under stress, there is developed a new phase or phases due to the altered orientation of the molecular complexes forming the structure.Mr. Poole, in reply, said it was not necessary to stretch a colloidal system beyond its elastic limit before this phenomenon of creep occurred. This had been noted even with very small loads. What is claimed for this manner of treatment of the results is that the two effects of viscous flow and the type of flow referred to by Dr. Mardles are separated and can be distinguished. Mr. A. de Waele asked whether Mr. Poole and Dr. Mardles could bring into line this stretching of a gel system, such as a gelatin gel, with the observed behaviour of the flow of a heterogeneous system through a capillary.He had studied this latter question extensively, but the conception of the phenomenon in terms of the extension was rather unfamiliar to him. I f one plotted a pressure applied against a volume extruded through a capillary, a curve was obtained which was parabolic in character. In some cases, e.g. suspensoid sols, the closeness to unity of the exponent in the parabolic flow law v4 = constant, might cause the P/V curve to simulate a straight line at its upper regions, thus ac- counting for the erroneous conclusion arrived at by many earlier observers as to the hyperbolic nature of the curve. However, many heterogeneous systems, and in particular those in which the 4 exponent was considerably less than unity, would yield P/V lines which, when plotted, showed not only obvious parabolas, but extrapolated to the P axis at some definite value above zero.Such was characteristic of self-healing gels or heterogeneous systems which had flocculated, the intercept corresponding to a definite static friction or imperfect elasticity, which would be accounted for in the equation : f m t - N S t o # - FIG. 2. P P - e -- v+ = a constant where e corresponded to the value of the intercept on the P axis. Henry and le Chatelier, Comfits. Rendus, 1920, 171, 16, 695. Mardles, Trans. Far. SOC., 1923, 19, 118.2 7 2 PROBLEMS RELATING TO TEXTILE FIBRES Dr. Mardles said it was not an easy matter to give a satisfactory answer because the whole problem was so complicated, and with colloidal systems many of the physical measurements were variable with time, e.g.surface tension and elasticity measurements. As to the flow of hetero- geneous systems through capillaries, there again there were so many factors which apparently influenced the results that it was necessary to be cautious in explaining the intercept on the axis, viz. the yield value. The phenomenon had been described by a number of workers with different substances, e.g. solid clay systems, lead, etc. (Ackermann), whilst Bingham has observed the effect even with dilute sols of cellulose nitrate. Further investigations were necessary before a concise and satisfactory explanation of the phenomenon could be given. Mr. A. de Waele said that Bingham’s curve was of the type of a hyperbola and showed a mixture of elasticity and pure viscous flow, which latter was linear.From experiments which he himself had carried out on numberless heterogeneous or plastic systems the curve he obtained was in the nature of a parabola. More recent workers on the subject had shown that flow of a colloidal system through a capillary to be a question of elasticity and viscous flow but with carefully regulated ex- periment one found that the exponent of the volume extruded was always fractionally less than unity. Bingham’s work had been in no way sub- stantiated. A considerable number of writers had experimented on the lines of Bingham but his results had not been substantiated in any way whatever. Dr. A. E. Oxley dealing with Dr. Barratt’s paper on the lustre of cotton yarns, said he and Mr.Adderley had investigated the lustre of double yarns and found that they had a maximum lustre when the fibres were parallel to the axis of the double yarn. That was a point in keeping with Dr. Barratt’s work, who had found that the lustre of the fibre was a maximum when the light is incident along the direction of the fibre. This brought out another point which had been somewhat overlooked, so far as the papers which had been read were concerned. I t was known that one could start with a cotton which was less lustrous than another cotton and by spinning and doubling it one could make of the less lustrous cotton a more lustrous yarn. For this reason he thought that the recom- mendation that had been made by Dr. Balls in his introductory address, that physical research should commence with the raw material, was rather a mistake, at any rate in a case like that.In the case he had mentioned they might start OR with a poor material and yet make a product which was more saleable than that made from a more lustrous material if only the later processes were carried out correctly. That was a question of physical research applied essentially to spinning and doubling problems, the lustre being measured by purely photometric measurement. Here we were not concerned only with the lustre of the raw material but with the lustre of the final product. That was only one case where physical research on what might be called the “position” of the textile fibre had a wide application apart from the actual property of the fibre.Other cases included, for instance, the question of high and low draft yarns. Again, as regards the regularities of yarns spun from high and low grade cottons, although the properties of the raw materials were quite different, resulting in different absolute breaking loads, yet the percentage variation in the final saleable product was approximately the same in the two cases. That was a case of drafting of fibres which was worthy of physical investigation and for this and other reasons he felt there was a very wide application for the work of theDISCUSSION 273 physicist in the industry without necessarily starting on details of the raw material. In following the line he had suggested, results would be obtained which would be of immediate benefit to the trade.The spinners should be shown the qualities of the yarns which they prepared under trade conditions from different cottons, perhaps involving complicated mixings, and that was an aspect of textile fibre research which should be emphasised in such a discussion as this. Dr. A. Barratt referring to Dr. Shorter’s paper said although the conclusions given in the paper as to complete recovery from strain might be correct for woollen fibres, he doubted whether they were to any great extent correct for any other fibres. I n fact, he doubted very much whether if a woollen fibre were stretched 40 per cent. it would, in any length of time, come back again, and referred to the stress-strain diagrams in his paper on the “Fibre Balance ” where there appeared to be permanent elongations up to 2 0 or 30 per cent. in the case of woollen or silk fibres.He would like to ask Dr. Shorter whether he had stretched fibres as much as 40 per cent. and found that they came back to their original length. Dr. Shorter said he would not care to say definitely that stretching to the extent of 40 per cent. had taken place but it certainly had been up to 25 per cent. and the fibres came back to their original length, As to the point raised by earlier speakers concerning gelatin, a wool fibre was a very different thing from a strip of gelatin. If a wool fibre were wetted, it did not swell like gelatin, whilst a wool fibre could be oiled and the gelatin could not. Thus the two were very different, and he did not think it possible to get any quantitative laws which would apply to both of them.Mr. F. T. Peirce said this subject had been a matter of controversy for a long time and the most favoured hypothesis was that the effects are due to a reversible re-orientation of the particles of the mass. Other interpretations had been put forward during the past century but it was really a question whether there was any difference between the different views. The one was a mechanical analogy, and the other-which he regarded as the sounder view-was an explanation in terms of molecular dynamics. All such effects were determined by the properties of the molecules themselves and a real explanation could only be arrived at in terms of molecular dynamics. Mr. N. W. Barritt (communicated) : Though Dr. Balls’ career should be enough to convince anyone of the value of the biologist in industry, I think there will be few present who would not support his contention of the ultimate dominance of the physicist. With all due respect to the Faraday Society one might be tempted to ask why the physicist is so long about it, and is apparently content to be led by the biologist. The happy coining of the term “ Trichodynamics ” gives more precision to the claim of the physicist to this new domain. This is one method of attack- ing the problems of the spinner but one must not lose sight of another method, also pioneered by Dr. Balls, which may perhaps be said to belong to the domain of “ Cytodynamics ”. Fibres must be grown before they are spun and the manner of their growth calls for as much research as their subsequent spinning. Problems of growth do conform to the laws of physics and chemistry and it is only by the application of these laws that biology can make real progress. When the physicist ultimately dominates biology we may hope to learn amongst other things why cotton has neps ” and wool its ‘‘ noils ”.

ISSN:0014-7672    

DOI:10.1039/TF9242000269

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No.13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. PART 11. THE FIBRE BALANCE. BY THOMAS BARRATT, D.Sc., F.INsT.P. (RESEARCH DEPARTMENT, WOOLWICH). Received May I 6th, I 9 2 4. An apparatus designed for the measurement of the breaking stress, extensibility, and recovery from strain of single textile fibres was described by the author in 1gz2.l A perspective view of an improved form of the ‘‘ Fibre Balance ” is given in Fig. I. The fibre A, whose properties are to be examined, is mounted by means of cycle cement between smalI paper squares, and one end of it clipped in a movable clamp C, hung from one of the knife edges of the balance.A second clamp BD, which can be moved up or down by means of a rack and pinion arrangement, grips the other end of the fibre. The extremities of these two clamps are of such a shape that the fibre is held quite tightly at points a definite distance apart. Suspended from the other knife edge of the balance is a solid rod K of very soft iron (“Lowmoor”), 11.3 crns. long, 0.63 cm. diameter, and of weight 28 gms. With the beam of the balance horizontal, 10-3 crns. of the length of this rod is inside a solenoid L of covered copper wire, through which an electric current can be sent so as to exert a pull on the fibre, owing to the attraction between the solenoid and the magnetised iron. The amount of this current can be varied by means of sliding rheostats, and measured by a sensitive milliammeter, suitably shunted.The weight of the rod is counterbalanced by an adjustable brass disc E. A thin brass rod H (dotted in the diagram), with a movable weight, serves to adjust the equilibrium of the balance beam to which it is attached. By this means it is arranged that the beam is very nearly in neutral equilibrium, so that the pull on the fibre is practically independent of the position of the beam. By hanging weights from 0.05 gm. to 15 gms. from the left-hand knife-edge, and observing the corresponding balancing currents as given by the milliammeter, a curve has been constiucted connecting the pull on the fibre with ‘‘ Readings on Ammeter.” I n order to measure the extension of the fibre at any given instant, two plane mirrors F and G are employed (see Figs.I and 2), F being attached to the moving beam and G to the central fixed pillar of the balance. A ray of light AB-GH (Fig. 2) is reflected three times from each mirror and then falls on a millimetre scale I 5 0 crns. away. I t can easily be seen that if the mirrors are at an angle a then the ray AB is turned through an angle 6a after the six reflections. I f then the mirror F is rotated through a small angle iSa, the ray GH rotates through an angle 68a. (See Fig. 3.) ’ ~ o u r n . Text. Inst. Proc., Jan. 1922. 274THE FIBRE BALANCE 2?5 A further magnification is given by the ratio (distance of mirror from scale)/(half length of balance arm), and the total manification is found to be 126 (see Table 11.).That is, an extension of I mm. in the fibre gives a movement of the spot of light of 120 mms. \ '- I / FIG. 1.-The fibre balance. The fibre experimented upon can be immersed in any required liquid by placing a beaker of the liquid in the position shown by the dotted lines. The clamp BD was given its '' U '' shape for this purpose. Some interest- ing measurements of the contraction of single cotton fibres in caustic soda solutions have been thus carried out.' 1 Willows, Barratt, and Parker, '+~nr. Text. Inst., XIII., 12, 1922.THE FIBRE BALANCE Calibration of the Balance. (I) Connection Between Reading of Ammeter and PuZZ on Pidre. The points investigated were :- ( a ) Reading of ammeter for various stresses with the balance beam horizontal (Fig.3). FIG. 2.-Double mirror arrangement for measuring extension or contraction of fibre. (6) The variation in these results when the soft iron armature is sucked (c) Variations due to hysteresis in the armature. further into the solenoid (Table I.). FIG. 3 . 4 u r v e connecting ammeter reading with pull on fibre. Weights from 0.05 gm. to 15 gms. being suspended from the left-hand knife-edge, the reading of the ammeter was taken with the spot of light at 0, at 2 0 and at 60 cms. (The beam was horizontal with the spot at 2 0 , and the whole range from o to 60 corresponded to an extension of the fibre, or a movement downwards of the armature into the solenoid, ofTHE FIBRE BALANCE Pull in Gms. 0.05 0'70 0'20 1'00 277 Position of Spot. 20 20 20 0 20 0.5 cm.) case where the spot is at 2 0 (beam horizontal).The results given below (Table I.), are shown in Fig. 3 for the A reading 13.7 on the ammeter corresponds to a current of I ampere. Current Increasing. TABLE I. Current Decreasing. Current Increasing. 9'85 10'38 10.85 I 1-42 I I -85 12-38 12.80 Ammeter. 0.60 1-35 2-70 3-10 3.18 3'35 4'45 4'5 5 4-70 5'52 5-62 5'75 Current Decreasing. 9'72 10'25 10.73 I 1.28 11.70 12.65 12-22 Pull in Gms. 5-00 7-00 10'00 15.00 ?ositioa of Spot. I Ammeter. 0 20 60 -2 0 60 0 0 20 0 20 60 60 7.10 7.22 7'45 8'50 8.62 8.86 10.25 10.38 10.70 12.65 12.80 13-16 As most of the pulls measured were of the order 4 or 5 gms. it is fortunate, in this arrangement, that the ammeter is much more sensitive for small stresses than for larger ones.The position of the armature within the solenoid is seen to have some slight influence on the amount of the pull on it, but as this position seldom differed by more than I mm., it was not often necessary to take it into consideration. To measure the effects due to hysteresis in the armature, readings of the balancing current for various weights were taken ( I ) with increasing currents, (2) with decreasing currents. The results are given in Table IL, and it is clear that, owing to the extreme softness of the iron, only a small correction is necessary on account of hysteresis effects. TABLE 11. Pull in Grams. Ammeter Reading. 3-18 4'55 5-62 6'46 7-22 8-00 8-62 9-20 3-10 4'45 5'50 6'34 7-1 I 7'90 8-50 9-10 Pull in Grams. 9 I0 11 12 I3 I4 I5 Ammeter Reading.The method could easily be employed to give a rapid and accurate determination of the hysteresis curve of a sample of iron or steel. (2) Measurement 4th (( Magnsjfation " of l%re Exten&on. In order to measure the ratio of the movement of the spot of light on cathetometer microscope, reading to 0.002 cm. The following observations278 -- THE FIBRE BALANCE (Table III.), were made of simultaneous positions of the spot of light and readings on the cathetometer scale. Readings taken upwards and down- wards agreed within errors of observation. TABLE 111. Readings of Cathetometer. 1.084 0 ~ ~ 1 4 0'832 0.748 0.666 0.584 I'OOO 1 Differences, 1 Cms. 0.084 0.08 6 0.086 0'082 0.084 0.082 0-082 Readings of Spot, Cms. - I0 20 30 40 50 60 Differences, 1 Cms. I - I0 I0 I0 I0 I0 I0 Magnification.- 119 116 I22 I22 The mean magnification is 120. Measurements on Various Fibres. Stress-strain Diagrams. The method employed in obtaining stress-strain diagrams of single fibres is as follows :- The fibre, mounted as described above, is clipped in the upper clamp C . The lower clamp B is then adjusted by means of the rack and pinion ar- rangement so as to grip the upper part of the lower paper square. The beam is then set free by lowering the supports in the usual way, the current through the solenoid being sufficient to exert a small known pull (say 0.01 gm.) on the fibre. The lower clamp is moved by means of the rack and pinion until the spot is at a convenient pckt on the scale. The pull on the fibre is increased or decreased at will, and simulianeous readings taken of the ammeter and of the spot of light.From these readings (reduced to grams pull and percentage extension) the stress-strain diagram is easily constructed. Diagrams obtained in this way for various textile fibres are given in Figs. 4 to 11. The results found vary greatly from fibre to fibre, and those shown in the diagrams are chosen out of a large number as beihg roughly representative of average values. The properties exhibited by the curves are (I) breaking stress; (2) total extension; (3) recovery from strain. The last named property, which is taken as the percentage recovery in the length when the pull on the fibre is diminished by one gram, is easily obtained from the diagrams, being the tangent of the angle of slope of such a line as AB in Figs.4 and 5. Values obtained from Figs. 4 to 11 are given in Table IV. TABLE IV. Fibres. Cotton, Egyptian Sliver (unmercerised) Gun-cotton . . . . . Bog Cotton . . . . Artificial Silk (Viscose) . . . Linen . . . . . . Silk . . . . . . Wool (Merino top cap) . . . 9 9 3 9 ,, (mercerised) Breaking Stress. Gms. 8.0 5'4 2-8 4'2 10.9 23-0 4'6 7'2 I Extension Per Cent. -I 8.0 13.6 2-6 5'1 21.7 38.0 6.4 12'2 Recovery from Strain. (Percent age per Gm.) 0.42 0.67 0-8s 0'47 0.42 1.4 1'7 0'12THE FIBRE BALANCE 279 The mercerised cotton (mercerised without tension) shows an increase in extensibility of 7 0 per cent., and an increased recovery from strain of 60 per cent., over the unmercerised cotton. The guncotton also shows a large increase in recovery from strain, but a decrease in extensibility and PULL ON FIBRE (GRAMS). WLL ON FIBRE (GRAMS).. FIG. 4. FIG. 5. in breaking stress. The guncotton fibre is more brittle, and the mercerised one less brittle, than the untreated cotton. The wild variety of cotton (bog-cotton) shows a decrease in strength and in extension, but a slight increase in recovery from strain. Artificial silk (viscous) is more extensible than (unmercerised) cotton, with a recovery about equal to that of cotton. PULL ON FIBRE (GRAMS). FIG. 6. FIG. 7. Its breaking stress per unit area is however less than that of cotton, as the mean sectional area of the viscose was four times that of cotton, while its breaking stress was not more than I* times as great. The most remarkable contrasts, however, which incidentally throw much light on the known pro- perties of the threads and fabrics concerned, are to be found in the fibres2 80 THE FIBRE BALANCE of linen, silk, and wool.Linen is strong, but of very small extensibility, while its recovery from strain is about a quarter that of cotton, and only one-fourteenth that of wool. Wool and silk-especially the former PULL ON FIBRE (GRAMS). FIG. 8. -have a very high extensibility and recovery from strain as is shown in Table IV. and in the stress-strain diagrams. The plasticity of all the fibres examined is another noteworthy property. For example, on stretching a wool fibre (see Fig. 11), 32 per cent. of its original length, and then removing the stress, the fibre regained only about g per cent. of its length.In the case of other fibres this property is even more marked. I t was remarked by E. A. Fisher1 that “the elongation produced in threads (worsted yarns) by tension is very largely a permanent elongation.” The author considered this elongation to be due to the ’yourn. Text. Inst., Oct. 1921.THE FIBRE BALANCE 281 slipping of the fibres, but the results above show that it can be explained just as well by the permanent increase in length which is undergone by the individual fibres. n 22 21 20 I9 18 17 16 15 ib 13 12 II '10 9 <a 87 2 6 25 00 & 4 b3 s2 E l z x w o 1 2 3 4 5 6 PULL ON FIBRE (GRAMS). FIG. 10. FIG. 11. Mercerisatlon of Single Cotton Fibres. Numerous variations in the process of mercerisation of cotton are em- ployed in practice. Some of these have been imitated on single fibres in the present series of experiments.I n order to obtain lustre the fibres com- prising the thread or fabric being mercerised must be stretched at some part of the process. The object of the experiments described below was to ascertain :282 THE FIBRE BALANCE (I) the force required to stretch the fibre to its original (dry) length after it had been allowed to contract during mercerisation (or, in one case, the force necessary to keep the fibre from contracting at all during mercerisation) ; (2) the force required to break the fibre under the same conditions as those used in stretching it in ( I ) ; (3) the total percentage extension of the fibre before breaking. The following variations in the method of mercerisation were tried : 1st Method:-The fibre was mercerised loose, and the contraction The fibre remaining in the mercerising solution, was stretched to 2nd Method ;-Fibre mercerised loose, and contraction noted.Fibre 3rd Method :-Fibre placed in mercerising liquor (NaOH 35’ Tw.), I t was It (the NaOH solution being of density 35’ Tw. in every case). noted. its original length, and then further stretched until it broke. then placed in water, and stretched. and the pull on it so adjusted as to keep the fibre at its dry length. then stretched until it broke, as in the other methods. was then placed in one of the following :- 4th Methud:-Fibre mercerised loose, washed, and allowed to dry. (a) Air. (6) Water. (c) Caustic soda 3 5 ’ 3 ’ ~ . (d) Absolute alcohol. ( e ) Benzene.cf) Ether. and stretched as before. The fourth method described above is that of Dollfus, Mieg et Cie, F.P. 267459/1897. “The yarn is mercerised loose, washed, dried, and if necessary stored, when it loses 20 per cent. in length.” (N.B.-This shrinkage is due not only to fibre shrinkage, which is only about 5 to 7 per cent., but also to increase in fibre section, and consequent shrinkage of yarn,) “While dry the yarn can only be stretched without rupture 5 to 7 per cent., but if the yarn is treated with water, steam, alcohol, ether, or benzene, the original may easily be regained.” The following results were obtained in the cases mentioned above, each figure given being the mean of only about twenty measurements, so that no great degree of accuracy can be claimed.The three results given in each case refer to ( I ) The force required to stretch the fibre to its original (dry) length ; ( 2 ) The force required to break the fibre ; (3) The total percentage extension of the fibre. 1st Mefhud:-0-30 gm. ; 3.8 gm. ; 12-4 per cent. 2nd Mefhod:-o-85 gm. ; 5-6 gm. ; I I -3 per cent. 3rd Method:-o.17 gm. ; 4-6 gm. ; 12.1 per cent. 4th Method :-2 (a) 3-20 gm. ; 5-7 gm. ; 13.3 per cent. (b) 0.975 gm. ; 5-6 gm. ; 23-8 per cent. (c) 0.30 gm. ; 4-2 gm.; 26-5 per cent. (d) 2.78 gm. ; 4.4 gm.; 6.6 per cent. (e) 2.89 gm. ; 5.9 gm. ; 13-0 per cent. v) 3.7 gm. ; 5-7 gm. ; 10.4 per cent. 1 Clibbens, Shivlejf Inst. Memoirs, Aug. 1923, p. 161. 2 The percentage extensions given in the fourth method are rather exaggerated, as they are reckoned from the length of the dried fibre after shrinkage in the mercerising soh tion.THE FIBRE BALANCE 283 The most interesting results brought out in this series of measurements are : (I) The comparatively small force (0-17 gm.) required to keep the fibre stretched while being mercerised. Nearly double this force is required when the fibre is allowed to contract in the mercerising solution. ( 2 ) The increase in the pull required to stretch the fibre when the stretching is postponed until the washing operation. (3) The comparatively enormous pull required when the fibre is placed in air, alcohol, benzene, or ether. (4) The large percentage extension of the fibre before breaking when immersed in the caustic soda solution. The results would appear to indicate that for lustre effects in yarns or fabrics the stretching should be done in caustic soda solution. This would give the required fibre extension with the least possible amount of force, and would therefore not involve so much displacement of the fibres by tearing them apart from each other. I t would also permit a greater total extension, with consequent increase of lustre due to a more circular section of the individual fibres. Another obvious advantage of the greater total extension is the increase in the length or breadth (or both) of the yarn or fabric concerned. My thanks are due to the Director of Artillery, who has kindly given his permission for the publication of this paper. Physico- Chmical LaJoratory, Research Department, Woolwich.

ISSN:0014-7672    

DOI:10.1039/TF9242000274

出版商:RSC    

年代:1924

数据来源: RSC

摘要:

118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point.These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order.The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No.13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility. The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure.This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13.118 ELECTRICAL THEORY OF ADBORPTTON The writer considers the double layer as consisting of a swface of rigidly fixed atoms under continuous bombardment of positively and negatively charged ions, any particular point on the rigid surface becoming in turn negative, neutral and positive, these conditions arisdg in any order. The observed contact difference is the average effect of these conditions. Where several kinds of atoms are present in the solution the average number of any one of them at the surface will depend on their concentbration, valency and mobility.The variation of contact Werence from negative to neutral and positive was observed with cotton and aluminium sulphate near the neutral point. These variations occurred during the same experiment, the readings being direct measurements of E.1I.F.s developed by filtration under pressure. This point would be covered by putting n2 = 1 and = 2 or 3 in Mukherjee’s equation No. 13. THE ACTION OF LIGHT ON TEXTILES. BY GUY BARR, B.A., D.Sc. (NATIONAL PHYSICALABORATORY). Received May 2 and, I 924. The discussion of the experimental results which are here reviewed will be simplified if it is prefaced by an examination of the character of the light with which we have to deal. Practically, of course, interest centres in the action of sunlight on textiles, but sunlight, especially in this country, is of such irregular occurrence and of such variable intensity that a scientific study of its photochemical action is beset by great difficulties.The difficulties are particularly great when the reaction to be studied is very slow or the means for following the course of the reaction relatively insensitive. Whereas it is possible to investigate with some precision the darkening of silver bromide or the change in volume of a mixture of chlorine and hydrogen on illumination, processes which are so rapid that by selection of suitable times the intensity and character of the light may be kept constant during the period required for exposure, the effect of sun- light on textiles has hitherto been followed only by determinations of tensile strength and by such semi-qualitative and poorly understood reactions as the increase in absorption of methylene blue by cotton.For such work exposures not of seconds but of weeks are necessary to obtain measurable changes. Methods used in Exposures to Sunlight. When the attempt is made to investigate the distribution in the solar spectrum of the photochemically active rays, the variability of the material to be studied, a variability which it is unnecessary to emphasise at such a meeting as this, introduces further difficulties. From first principles the obvious method would be to resolve the light into its spectrum by means of either a prism or a ruled grating and to throw the spectrum on to a row of fibres of the textile, so as to avoid the complications which would be introduced by using the material in the form of yarn or fabric. The irregularity of the fibres would require, however, that an enormous number of separate fibres should be employed to obtain a reliable mean for the breaking strength, dye absorption, etc.; either a prohibitively large spectro- graph is indicated, or else the exposures of small quantities must be repeated ad nauseam, with the intensity of illumination varying from one exposure to the next. Spun yarn, more uniform than fibre, requires a smaller area of spectrum to give the requisite number of test-pieces, but even here the difficulty is by no means overcome. Although tensile tests on woven material show much less variability than those on yarns, the area of the 284THE ACTION OF LIGHT ON TEXTILES 285 test-piece is correspondingly increased.As a matter of fact the spectro- graphic method has been used by only one worker, and the results which he obtained with sunlight were negative. The use of absorbing screens has the advantage that much larger areas can be covered. The screens available are not, however, very satisfactory : the separation of the spectrum into relatively sharp bands by means of dyed gelatin filters is here inapplicable since the exposures required are so long; the length of exposure is increased by the imperfect transparency of the screen to the selected rays and the dyes are not fast enough to with- stand a year’s continuous sunshine. Glass filters transmit rather broad bands and the range of screens which can be obtained is very limited.Solutions of stable substances might possibly be prepared with rather better defined absorption limits and used at the sacrifice of some convenience of manipulation. Valuable though necessarily incomplete information has been obtained by the use of glass screens in sunlight. A third method of attacking the problem has given results of consider- able immediate practical value but of still less precise interpretation. This consists in the application of dyes to the textile itself. The fibres are thus exposed to white light on the exterior surface and the intensity of the rays absorbed by the dye is continually reduced as successive layers of the fibre are traversed. Under these circumstances the light available for the stimulation of the reaction is ill defined in character and intensity and the correlation of the changes occurring with the absorption spectrum of the dye is further complicated by the possibility of chemical or physico-chemical interaction between the fibre substance, the dye and the products of the action of light on either of them.The Mercury Arc in Quartz. The inconstancy of sunlight, as regards both intensity and composition, and the hope of accelerating the photochemical action by the use of an artificial source particularly rich in actinic light has led many investigators to study the action of light by means of the mercury arc in quartz. Although it is possible under suitable conditions to effect a relatively rapid deterioration of a textile by this means, it is not permissible to apply the results to the explanation of the action of sunlight except with very many reservations. I t is unnecessary to labour the difference between the mainly line spectrum of the mercury arc and the continuous spectrum of sunlight or the fact that comparative exposures of various materials to the two sources of light very frequently disagree even in the order of permanence which they assign to them, since these points have been dwelt upon at some length in many places.I t may be well, however, to lay some emphasis on the fact, which is not so widely appreciated, that the mercury arc is by no means constant in its emission. Differences in pattern and size, in voltage drop and in current consumption, cause very large differences in the ratio of intensities of various series of lines,l so that it cannot be assumed that the distribution of energy in the spectrum is given for any lamp by the experiments of Ladenburg2 Further, the light emitted becomes gradually weaker in ultra-violet rays, especially in those of very short wave-length, owing to changes in the envelope.The latter point is well illustrated by some photographs reproduced by A ~ t o n , ~ showing the differences in absorp- tion, between a new and an old quartz tube, and quantitative tests are recorded by the Bureau of Standards4 Notwithstanding all these defects, VOL. XX-TI0286 THE ACTION OF LIGHT ON TEXTILES some fairly definite information has been accumulated with the aid of the mercury-arc regarding the wave-length of the rays which are effective in the action of light on textiles. I t has been due in the first place to the development of aeronautics in the present century that the study of the deterioration of fabrics on exposure has been more actively prosecuted.The fact that window hangings, for example, become bleached and weakened in the course of time must have been obvious very early, to say nothing of the tendering of awnings, tents, etc., in which cases suspicion may attach to the ravages of fungi and bacteria in addition to sunlight : but the rate of decay is slow, at least in these latitudes, and the consequences of failure are economic only. But when the lives of men hung on an assemblage of threads, it became a matter of urgent importance to know more of the conditions under which light weakened textiles, of the rate of this weakening and of the means by which it may be minimised.Since linen and cotton have so far proved them- selves the most important textiles in aeronautical use, it is with these materials that the major part of the work has dealt. Work Prior to 1900. Girard,5 of hydrocellulose fame, ascribed the tendering of fabrics on exposure to the action of atmospheric acidity, citing in support of this generalisation a re- search by Dumas, 1846, who showed that the failure of some curtains in the baths at Aix la Savoie was due to oxidation of sulphuretted hydrogen on the surface of the fabric ; his own experiments in which pieces of paper and cotton were exposed in a sealed glass tube full of oxygen to several months’ sunlight appear to have been purely qualitative, for he remarks that he saw the exposed cellulosic material ‘‘ conserver toute sa solidit&.” Atmospheric acidity is, it is true, frequently responsible for the tendering of fabrics near cities, but in the country its effect has since been shown to be inappreciable.who was the first to use the methylene blue test in the characterisation of oxycellulose, was also the first to demonstrate that cotton responded to this test, after exposure to light. H e applied the dye to a set of samples of fine white muslin, containing very little dressing, which had been exposed from May to September immediately behind glasses of various colours. The intensities of shade, estimated on a scale from I : 10, are given below :- Two papers published previous to 1900 call for comment.Witz Colour of Glass. Intensity of Shade. Violet . . . . Blue, absorbing part of violet Green . . . . . Colourles . . . . Blue, absorbing all violet . Yellow . . . . R e d . . . . . Orange. . . . . . . . I 0 . . . 8 . . . 4:. . . . 4 f v * :;ti . . . . . . . * 1’ . . . Iii H e concluded that the maximum of activity in the spectrum lay in the violet or near ultra-violet and, judging from the effect of accidental local wetting, that the oxidation was accelerated by the presence of moisture; paper gave very similar results. Witz also noticed that the presence of salts of iron and of copper increased the rate of formation of oxycellulose.THE ACTION OF LIGHT ON TEXTILES 287 Observations on Rubbered Balloon Fabrics. The advent of non-rigid airships and balloons in which the gas-contain- ing layer of rubber was supported on a light cotton fabric was responsible for further examination of the effect of light.In the first place it was found that the rubber perished very rapidly and since ultra-violet light was suspected to be the effective agent, Henri suggested that the cotton should be coloured yellow to reduce the intensity of the harmful rays reaching the rubber. Depending on whether the rubber was hot or cold vulcanised the cotton was padded with lead chromate or dyed with a suitable aniline dye. In investigating the weathering of balloon fabrics it was found at the N.P.L.7 that this protection was not only effective in reducing the rate of deterioration of the rubbcr, but that the strength of the textile was also better preserved.The interpretation of this result is complicated by the presence of the rubber, which is known to give rise to acidity when insolated, but the fact that colouring of the cotton increases its resistance to the action of sunlight was definitely established by the results of some exposures made in Somaliland for the author.s Cotton cloths ( I 2 0 grams per sq. metre), all of the same delivery to Messrs. the North British Rubber Company who kindly arranged for the preparation of the samples, were exposed for two months at Berbera and the losses in tensile strength determined; the strengths before exposure being about 56 lbs. per inch, those after exposure were as follows :- Pieces Submitted to Conditions of Pieces Submitted to Conditions of Steam Cure.Vapour Cure. Unprotected . . . . 30 lb./in. Unprotected . . . . 22 lb./in. Dyed yellow . . . . 36 ,, ,, Impregnatedwith lead chromate 41 ,, ,, Dyed alizarin red . . . 36 ,, ), Coatedwith aluminum powder 28 ), ,, Coated with aluminum powder 38 ,, ,, The yellow dye had faded somewhat, but that definite protection is given by each of the treatments is obvious from the figures: it is also obvious that it is the violet or ultra-violet rays which are most deleterious. Observations on Doped Linen Fabric. Captain Godfrey Paine, R.N., was responsible for the, inception, about the same time, of some tests reported from the N.P.L. in 1 9 1 4 ~ on the effect of using red glass instead of ordinary clear glass for the windows of aeroplane hangars.Doped linen fabric was exposed under glass for IOO days, starting in January, and the strength fell from 60 lbs./inch to the following values :- In Moist Air. I n Dry Air. Under white glass, 49 lbs./in. . . . 38 lbs./in. 9 , ruby 9 9 56 9 , 1, * * 55 9 9 Y 1 The above observations were sufficient to demonstrate that the deteriora- tion of cotton and linen on exposure to sunlight is mainly, at any rate, due to the action of violet or ultra-violet rays. The large differences in the life of textiles in the tropics and in this country (lo, l1) 12, 13) are con- sistent with this view, for although it appears to have been demonstrated 14 that sunlight reaching the earth'is of much the same composition on clear days when the sun is at the same angle, the number of clear days and the altitudes reached by the sun are both greater in the tropics, so that the intensity of ultra-violet is greater, not only absolutely, but also relatively to the total sunlight intensity.Aston l5 reproduces curves showing the288 THE ACTION OF LIGHT ON TEXTILES rate of deterioration of doped linen fabric over three month periods be- ginning in each month of the year, and also the mean of the total solar radiation recorded for the same periods : there is a reparkably close agree- ment between the form of the curves, indicating that at Farnborough the proportion of deleterious to total radiation is approximately constant when averaged over a quarter of the year. Effect of Diameter of Yarn. If loss of strength during exposure to the weather is chiefly due, under normal circumstances, to the action of ultra-violet light on the textile, it would be expected that the rate of weakening should be less for heavy yarns than for very fine counts, since the outer layers would tend to act as absorbing screens for the inner layers.That such a difference does, in fact, occur has been shown by several workers. For example, TurnerI3 found that a cotton fabric weighing 2.2 ozs. per sq. yard (150 ends, 146 picks per inch) lost 57 per cent. of its strength, while a duck weighing 10.3 ozs. per sq. yard (three-fold warp), lost only 15 per cent. during similar exposures in this country, and differences of the same order were shown by linen both at Farnborough and in Somaliland. In,exposures to a mercury arc lamp, Aston l6 noted a loss of 35 per cent. in the strength of a Linen thread which initially carried 216 ozs., while a washed thread having a strength of 78 02s.lost 63 per cent. of this strength. Distribution of Destructive Power in the Spectrum. To facilitate the search for means of reducing the rate of deterioration, it became necessary to examine in greater detail the distribution of destruc- tive power in the spectrum. Scheurer l7 had already extended the observa- tions of Witz (Zuc. cit.) by noting that the yellowing of cotton fabric under a quartz mercury arc was greatly retarded by the use of a thin glass screen, whereas a quartz screen appeared to make no difference: he concluded that tbe oxidation was due to rays comprised within the limits 1860 to 3000 A.U.This deduction appears to have been made from qualitative observations : it was partially confirmed by tensile strength tests made on doped linen fabric l8 under similar conditions ; the shielding effect of glass is not so marked in sunlightY3 where the ratio of extreme ultra-violet to the longer ultra-violet is smaller. exposed linen thread in the plate holder of a quartz spectrograph to the resolved light of a mercury arc for four weeks. The amount of material was not sufficient to enable an ac- curate mean value to be obtained for the breaking strength in different parts of the spectrum, but he used as criterion of the deterioration the proportion of threads breaking in the exposed portion, which was one-sixth of the tested length of each thread: where no weakening had occurred one thread in six might be expected to break in the exposed part; if the pro- portion was higher the light was presumed to have caused deterioration.The spectrum covered 138 threads (including regions where no lines are recorded) and only 35 threads broke inLhe exposed portion : 6 of the 35 lay in the width covered by the 3660 A.U. line, and in the direction of longer wave-lengths up to the yellow, only 3 out of 37 broke in the exposed portion. The intensities were therefore insufficient and the criterion of change too insensitive to prove much more than that light of wave-length 3660 A.U. and probably also h 3130 and h 2570 will weaken linen. This experiment was repeatedIG with linen and cotton threads and sunIight AstonTHE ACTION OF LIGHT ON TEXTILES 289 exposure, the image of the sun being focussed on the slit by a quartz lens and the whole mounted on a clock-driven equatorial at Greenwich, but after 1 1 1 and 2 0 0 hours respectively of recorded sunshine no positive indication of weakening was obtained.It was noted, however, that bleaching of the linen threads was marked in the region 3000 A.U. to 4200 A.U. It was considered from these experiments that the weakening of cellulosic thread; on exposure was chiefly due to the rays of wave-length less than 4000 A.U. This conclusion has been verified by Ramsbottom and Glendinning l9 by means of coloured glass screens, whose transparency to various regions of the spectrum was compared by photographs of the iron arc spectrum taken through them.Doped linen was exposed for 2; years under the various screens and the deterioration determined by means of strength tests. In Table 111. are given the characteristics of the screens and the breaking strengths of the fabric after exposure : the strength Colour of Glass. Red . . . . . Orange red . . . . Green . . . . . Orange . . . . . Blue green . . . . Yellow . . . . . Purple . . . . . Violet . . . . . Clear . . . . . Blue . . . . . No glass . . . . Wave-lengths Tra smittcd in Iron Arc. 1 . U . 62 50-5550 6300-4900 5600-4650 6300-3320 (weak from 4600 to 3800) 5 500-3500 6300-3150 (denser than orange 4600 to 3150 but weaker than blue green 4600 to 3800) 6100-5000 and 4300 to 3320 (denser than yellow 4000 to 3320) (very dense 6300 to 3270) (very dense) 6400-3140 (very weak 6400-5400, weak 5400-4600, equal to clear glass 4600-3 140) 6600-2 I 60 6300-3230 6400-3 100 Breaking Load of Linen, lbs./in.I02 98 89 56 47 I4 I2 8 6 4 2 before exposure was 120 lbs./in. The authors note that a close approxima- tion to the order of transparency to rays which are destructive to cellulose is given by comparing the actinic transmission as measured by photographic printing papers; this followed an observation made by the writer on some painted fabrics exposed in Egypt. In a lecture delivered to the Royal Aeronautical Society in January of the present year, Dr. Ramsbottom 21 mentioned an additional fact which serves to narrow down the range of wave-lengths which may be considered operative in causing loss of strength by exposure to light. He found that linen threads enclosed in a glass tube and exposed for half a year lost 48 per cent.of their strength while similar threads in a quartz tube lost 5 0 per cent. of their strength during the same time. Since glass transmits very little radiation below X 3 2 0 0 and shows marked absorption even at X 3300, this indiptes that, in English sunshine, rays having a wave-length less than 3 2 0 0 A.U. are of little importance as regards their weakening290 THE ACTION OF LIGHT ON TEXTILES effect on linen. There is an apparent discrepancy between this result and the experiments already mentioned, by Scheurer17 and at the Royal Aircraft F a ~ t o r y , ~ in which glass was found to cut off practically all the deleterious rays when fabrics were exposed to a mercury arc lamp: the reason is presumably that cellulose is eztremely sensitive to the rays of very short wave-length (less than 2900 A.U.) which are present in the light of the mercury arc but are absent from sunlight: the rays emitted by the former source include those which are capable of converting oxygen into ozone. There is a small amount of evidence pointing to an antagonistic action between rays of different wave-length.Thus both by the oxycellulose test on Witz's samples of cotton (p. 286) and by the strength test on Ramsbottom's doped linen fabric (p. 289) colourless glass appears to give greater protection than blue : the actual values of the strength in the latter experiments were, however, too low for accurate comparison, and a result (unpublished) by the same worker indicated no difference in deterioration when threads were simultaneously exposed 7 ins.from a mercury arc and to the same arc plus red light. Aston's spectrum experiment, de- scribed on p. 288, may be construed as possibly indicating increased strength in the threads exposed in visible regions. Antagonism between the action of different rays on moistened unbleached cotton is described by Pech,20 who found that the time required for similar loss of colour could be doubled by increasing the amount of visible light incident on the specimen by means of reflectors disposed round the mercury arc : extrane- ous light rich in infra-red, sunlight or light from a carbon arc filtered through a glass screen also delayed the bleaching.From the fact that linen threads were more bleached. when shielded from a mercury arc lamp by clear, blue green, or blue glass than when unprotected, although the unprotected threads alone showed any loss in strength,19 Ramsbottom and Glendinning conclude that in all probability the two processes involved are due to totally different reactions. The Changes are Mainly Due to Oxidation. The nature of the physico-chemical changes produced in cotton and linen by the action of light have been studied by several investigators. In the case of linen the observations have been compiicated by the fact that the fibres contain a larger proportion of non-cellulosic material : the bleaching of this in sunlight is a matter of everyday experience and it has been shown that bleaching may be very marked when there is no detect- able loss in strength.It has been shown by numerous experiments made at the Royal Aircraft Establishment 18* 3 1 21 that the photochemical reaction leading to loss of strength in sunlight is almost entirely inhibited in the absence of oxygen, though there is slight weakening of the threads when exposures are made in uacuo or in an atmosphere of hydrogen in close proximity to a mercury arc. The behaviour of cotton might be expected to be more readily followed. After long continued insolation white cotton fabrics acquire a yellowish tinge. Witz,'j as mentioned above, observed that cotton exposed to sunlight behind various glass screens answered the methylene blue test for oxycellulose. Scheurer l7 found that after illumination by a mercury arc a cotton fabric became yellow, except where it was protected by a glass screen, and not only gave an intense colour inTHE ACTION OF LIGHT ON TEXTILES 291 the methylene blue test but also reduced Fehling’s solution.Harrison 22 stated that in addition to oxycellulose a soluble organic substance was produced which was acidic and had reducing properties. Working with a scoured and bleached airship fabric OorCe and Dyerz3 made both qualitative and quantitative experiments on the yellowish product of ex- posure to a mercury arc, which appear to indicate a substantial similarity to the oxycellulose prepared by the action of ozone. I t has been remarked, both for linenls and for ~ o t t o n , ~ ~ , ~ * that the microscopical appearance of the fibres is very little affected even by severe exposure. DorCe and Dyer noticed, however, that their material showed some transverse cracks and swollen portions, and they comment also on the fact that the exposed cloth was absorbent and sank immediately in water, -in marked contrast with the original fabric.Lindemann’s 6‘ Quantum ” Explanation. The mechanism of the action of ultra-violet light is obscure. Ramsbottom showed that the loss in strength of linen threads exposed to sunlight in sealed glass tubes was two to four times as great in oxygen as it was in air, being insignificant in a high vacuum, in hydrogen or in carbon dioxide. Though the loss is more rapid with the air or oxygen saturated with moisture than when dried with phosphorus pentoxide, im- mersion of the specimen in water saturated with oxygen causes the reaction to proceed very slowly.The oxidation in sunlight is not due to a normal formation of ozone, since the rays which convert oxygen to ozone are not present in the light which reaches the earth from the sun. Lindemann3 put forward a hypothesis which assumes that ionised oxygen is responsible for the oxidation : using the quantum relationship, he calculated from the measured ionisation potential of oxygen and an approximate value for the dielectric constant of cellulose deduced from the refractive index, thato the most effective wave-length should be in the neighbourhood of 3230 A.U. Similar arguments applied to the rays owhich decompose ozone, having normally25 a wave-length about 2570 A.U., would suggest 26 that red or orange light should tend to counteract the effect of the deleterious rays on cellulose: the evidence for this antagonism is at present somewhat flimsy.The action of light on cotton is accelerated, as is well known, by the presence of iron, and also, according to experiments by the writer, by uranium and tungsten: castor oil has also a weakening effect,ll though much of this may be due to chemical attack. A criterion for detecting changes in cellulose which is much more sensitive than the mechanical or tinctorial tests used hitherto is provided by the measurement of the viscosity of a cuprammonium solution, a test, due to Ost, which was developed in the laboratory of Woolwich Arsenal for the examination of cotton for nitration purposes. Miss Hadfield, working with the author, has recently made experiments which show that the viscosity in solution of a light cotton fabric is reduced to an easily measurable degree long before any definite change in tensile strength can be detected.I t is hoped that much information concerning the action of light on cotton may be obtained by the application of this method at the National Physical Laboratory.2 9 2 THE ACTION OF LIGHT ON TEXTILES Action of Light on Silk. The information available as to the effect of light on other textiles is scanty. The protection which is afforded to silk by the application of a proofing containing aluminium powder, as compared with a transparent proofing is illustrated by the behaviour of two oiled silk balloon fabrics of which one (the unpigmented) lost 36 per cent.of its strength in 1 2 0 days while the other lost only IS per cent.: but the samples were of very different construction. Turner l3 exposed various specimens of silk made from fine discharged yarns in England and in the tropics, and found that the effect of light was considerably more than it was with cotton or linen : for example, at Berbera a 4-02. net silk twill 2/1, discharged, lost 9 2 per cent. of its strength in IOO days, while a linen fabric of similar weight but plain weave lost only 64 per cent. (means of warp and weft strengths): similar differences were apparent after exposures made at Farnborough, where also a plain 2-02. net silk fell to pieces before IOO days were com- pleted. That the deterioration recorded was almost exclusively due to light is proved by the fact that it was very largely prevented, as in the case of cotton and linen, by varnishing the doped fabric with an opaque coating.Exposures to the mercury arc have been made by Aston,lG who found that silk threads lost 80 to 87 per cent. of their strength in 3 days at 23 crns. from the lamp, while a stouter linen thread lost 46 per cent. Vignon 27 compared Schappe silk with linen by a similar method and concluded that the former was much more resistant although in sunlight the losses in strength were equal. The writer,28 made exposures of doped Schappe silk and aeroplane linen to summer weather and found that under these con- ditions the Schappe silk was not much more affected than linen. The difference between the results obtained with net silk and with Schappe is apparently largely due to the extreme fineness and transparency of the former : for yarn of a given weight the initial sensitivity of silk is probably not much greater than that of cellulosic fibres.Weighted silk exposed by Ristenpart 29 from March to August fell to pieces and the fibroin in it was reduced considerably in amount: he noted that a Japanese silk treated with tannin was very much less affected. Waentig yo observed that a glass plate interposed between silk and a mercury arc lamp cuts out practically all the rays from the arc which are instrumental in causing deterioration. Action of Light on Wool. Wool appears to be remarkably slowly affected by light either from the sun or from a mercury arc ; Waentig was unable to demonstrate any very definite loss in strength of woollen yarns after 3 months’ summer exposure to sunlight or after 2 4 hours’ exposure at 2 5 crns. from his arc.Kertesq31 remarks however, that woollen cloth exposed to a mercury arc gave up to alkali more albuminous matter answering to the biuret test than before ; the destruction of the nap, which is the visible sign of deterioration, is similar to that occurring in prolonged exposure to the weather. H e con- cludes that actinic light is responsible for the change and proposes to give protection by impregnation with chromium acetate. Action of Light on Artificial Silks. exposed for 2 4 hours to the light from a mercury arc. Waentig29 tabulates the results of tensile tests on four artificial silks The losses inTHE ACTION OF LIGHT ON TEXTILES 293 strength were in each case less than for cotton, his figures for which are given for comparison : the rays producing weakening were, as with cotton, almost entirely cut off by glass.The table gives the mean breaking loads in grams. Egyptian cotton, unbleached . . . American cotton, unbleached . . . bleached . . . Line): bleacdkd . . . . . Nitro silk . . . . . . Viscose silk . . . . . . Acetate silk . . . . . . .. . . . 9 9 bleached Cuprammonium silk . . . . Unexposed. 1 Exposed. I 7'2 6.0 6.3 6.3 16-5 13'4 9'7 q8 4'4 3'0 2'2 2'0 1.6 7'3 12.5 8-5 9'1 2 '2 The difference in sensitivity between bleached and unbleached cotton had already been remarked by Aston.16 Action of Light on Ramie and Jute. These materials were included amongst those exposed by Turner l3 in the tropics and in England: he found that ramie was slightly, and jute much more sensitive to light than either cotton or linen, jute being superior only to silk. The comparison is unduly favourable to ramie and jute since the yarns used were very much coarser than those of the silk. It is impossible to conclude this review without acknowledging the assistance which has been derived from the summary by Cunliffe32 of the literature relating to the action of light on cotton. BIBLIOGRAPHY. 1 Kuch and Retschinsky, Ann. der Physik., 1906, 20, 563, 658 and 1907, 22, 852. 2 Physikalische Zeitschrift, 1904, 525. 3 Reports and Memoranda of the Advisory Committee for Aeronautics, abbreviated as R. and M., 396,1917. 4 Scientific Paper, NO. 330. 6 Bull. Sac., Rouen, 1883, XI, 188. 7 R. and M., 46,1911. sR. and M., 313, 1917. R. and M., 177, 1914. 10 Barr, R. and M., 179, 1914. 11 Atkins and Barr, R. and M., 318, 1917. 12 Atkins and Woodcock, R. and M., 519, 1917. 1:s Turner, R. and M., 582, 1919. 14 Freer and Gibbs, Yuurn. Physical Chem., 1912, 16, 709. l s R . and M., 430, 1917. la R. and M., 585, 1919. 17 Bull. SOC. Ittd. Mulhouse, 1910, 80, 324. * R. and M., 498, 1915, Appendix. EJ R. and M., 845, 1922. 90 Comptes Rendus, 1920, 170, 1322. 21 Ramsbottom, ~ o i w r i . Roy. Aeronautical SOC., 1924, 28, 273. 22 yourn. SOC. Dyers artd Col., 1912, 28, 225. ZIbid., 1917, 3, 17. Ann de Chim. Phys., 1882, 24, 337. VOL. XX-T10*294 THE ACTION OF LIGHT ON TEXTILES a Pennetier, appendix 10 (6). 36 Regener, Ann. der Physik., 1906, 20. 26 Barr, appendix to (19). 21 Comptes Rendus, 1920, 170, 1322. 98 Unpublished. 29Zeits. f. anpew Chem., 1909, 18. 30 Ibid., -1923;36, 357. 31 Textile Forschung, 1919, I, No. 3, and Zeits. f. angew Chem., 1919, 32, 168. =yourn. Textile Inst., 1923, 14, T. 314.

ISSN:0014-7672    

DOI:10.1039/TF9242000284

出版商:RSC    

年代:1924

数据来源: RSC