E. J. Bevan

“ The comparison of one paper with another with a view to ascertain the relative degree of sizing, is usually performed in a more or less rough and ready way by moistening the samples with the tongue for a certain time, and noticing the degree of transparency produced, which is of course inversely to the degree of hardness. A more accurate method consists in placing a drop of a mixture of alcohol and water containing some colouring matter in solution and determining the time necessary for the colour to make its appearance on the other side. ”

“ Plant tissues, however, seldom, if ever, consist of pure cellulose, but contain besides, other products of growth either chemically combined with the cellulose or mechanically bound up with the tissue, which are, according to the nature of their union, removable either by means of fundamental chemical resolution or by the application of simple solvents. A general method for the isolation of cellulose consists in exposing the moist tissue to the action of chlorine gas or of bromine water in the cold, and subsequently boiling in dilute ammonia ”

“ Esparto.—This fibre, on account of its high percentage of non-cellulose constituents, requires a large amount of soda to resolve it; on the other hand, being of the nature of a pecto-cellulose, the process of disintegration may be conducted at a low pressure; in fact, it is the practice at some mills to boil in open vessels, in which case, however, a larger amount of soda is required. As has been already stated, it may be taken as a general rule for all fibres, that within certain limits the higher the pressure employed the less soda is required. ”

“ One of the most characteristic of these modified celluloses constitutes the jute fibre, the isolated bast of an Indian plant, {17} which has an enormous industrial application for the coarser textile purposes. The chemistry of jute throws light on the course of lignification, the process by which cellulose is modified into wood, and in studying it in preference to wood we have the advantage of studying a simple tissue. ”

“ It is obvious that while the spinner has to do with these filaments, the paper maker works up the ultimate fibre constituents or fibres. It is also an obvious corollary from this distinction that a fibrous material which from “weakness” is unavailable for textile application, may yet be perfectly “strong” from the paper maker’s point of view; in other words, the individual fibres may be strong, but have little cohesion in the filaments. ”

“ A cheaper method, and one which is largely adopted in mills where only a coarse dark-coloured paper is required, consists in boiling the jute or other fibre in lime. Such a treatment is, however, not so effective as one in which caustic soda is used, and the fibre produced is harder and coarser in every way. The yield of pulp, however, owing to the fact that the fibre is imperfectly resolved, is greater. In many cases, from questions of economy, lime may be advantageously employed. ”

“ When a solution of gelatin is added to the liquors in which wood has been treated by any of the bisulphite or sulphurous acid processes, a body is precipitated in the form of a caoutchouc-like mass which can be dissolved in neutral sodium sulphite solution, or in weakly alkaline solutions, and can be reprecipitated on addition of alum to the solution. The substance consists of a compound of the gelatin with the non-cellulose constituents resembling, but not identical with, as has been supposed, the precipitate obtained by adding tannic acid to a solution of gelatin. ”

“ The presence of starch in a paper can be readily ascertained by its behaviour with a solution of iodine. If starch be present the well-known blue colour of the compound of iodine and starch will be produced. The determination of the amount of starch present is a matter of some difficulty, the details of which are somewhat beyond the scope of the present work. It is based upon the conversion of the starch into sugar, and the estimation of the latter with Fehling’s solution. ”

“ For the chemical identification of the fibres in a paper, the only available reactions are those with aniline sulphate solution. The majority of fibres (celluloses) give no reaction, straw and esparto celluloses and mechanical wood-pulp being the only ones that can be identified by its means. The authors have found that when a paper containing straw or esparto is treated for some time with a boiling 1 per cent. solution of aniline sulphate, a pink colour is produced. Esparto gives the reaction with greater intensity than straw. ”

“ This cement-like cupro-cellulose, as it may be termed, being insoluble in water, communicates water-resisting properties to the material so treated: moreover, the presence of copper renders the fabric less prone than before to be attacked by insects and mould, so that animal and vegetable life of a parasitic nature and fungoid growths are rarely, if ever, to be observed, even when the material is kept under conditions where boring worms, ants, rot, and mould, would be likely to attack it. ”

“ For boiling and bleaching purposes it undoubtedly is, as when mixed with caustic soda or bleaching liquor they form a precipitate of carbonate of calcium, which lines the insides of boilers, breakers, and potchers as a hard scale, which is always liable to become detached, and to find its way into the finished paper. Moreover, carbonate of calcium is precipitated in the fibre, and carries with it a certain quantity of colouring matter, the subsequent removal of which is difficult. ”

“ Whichever variety of “antichlor” is used an excess should be carefully avoided, as all act more or less upon the size and colouring matter added to the pulp subsequently. The proper method is to run in small quantities of a solution of the antichlor at a time, testing the pulps, after allowing a few minutes for complete admixture after each addition. The test is made by immersing a piece of iodide of potassium and starch paper, which will be turned blue so long as any calcium hypochlorite is present. ”

“ In making the finer kinds of paper, the roller bars or knives, instead of being made of steel are made of bronze, thus any contamination with oxide of iron is avoided. This is especially liable to take place in case of steel knives when the beater has been allowed to stand for some time. {120}
The inside of the heater itself is often lined with lead, a material which is not liable to oxidize, and which can very readily be cleaned.
When a beater has been running for some time the knives of the roll and the bed-plate become worn and so far reduced that they must be taken out and re-cut. ”

“ Having by analysis acquired a knowledge of the parts, we study their mutual relations in the structure they compose—we integrate our knowledge, so to speak—by means of sections of the structure, cut so as to preserve the cohesion of the parts in section, and yet in so fine a film as to appear under the microscope to be virtually a plane surface. These points are illustrated in the drawings given.
It is impossible for us to deal specially with the subject of the microscope and its manipulation. The microscope, as a revealer of natural wonders is one thing ”

“ Notwithstanding all the attempts that have been made, the use of a lead-lined boiler is a serious objection, and any process which will fulfil the conditions on which the bi-sulphite processes depend, and which at the same time admits of the use of the ordinary iron boilers, is an obvious desideratum. ”

“ The concentrated liquor is run on to either of the beds b, where the last portions of water are driven off by the heat from the fireplaces a, and the residual mass is ignited until all the organic matter contained in the liquors is carbonised and the soda is converted into carbonate of soda. This takes place in about 4 hours, according to the degree of concentration of the liquor as it is run into the furnaces. The running in of liquor should be done with great care, as explosions sometimes occur through the sudden liberation of steam on the liquor coming in contact with the hot beds. ”

“ To form a sheet of paper the workman dips the mould, with the “deckle” in position, into a vat containing the prepared pulp diluted with water, lifting up just so much as will make a sheet of the necessary thickness. As soon as the mould is removed from the vat, the water begins to drain through the wire-cloth, and to leave the fibres on the surface in the form of a coherent sheet of paper. The felting or intertwining is assisted by lateral motion in every direction given to the frame by the workman. ”

“ Mechanical wood-pulp, when treated with a solution of aniline sulphate, develops, even in the cold, a deep yellow colour. If a paper containing mechanical wood-pulp so treated be examined under the microscope, the fragments of wood will be found to be deeply stained, whereas the other {202} fibres remain colourless or nearly so. It must be borne in mind that cellulose obtained from lignified fibres, if the boiling and bleaching processes have not been carried sufficiently far, will give with aniline sulphate a more or less intense yellow coloration. ”

“ Amyloid.—When cotton is treated with 30 times its weight of sulphuric acid somewhat diluted (1 part H2O, 4 parts H2SO4) it quickly dissolves, the solution being at first gelatinous, becoming afterwards syrupy. On pouring this solution into water, a white flocculent precipitate is formed, consisting of a substance closely resembling the cellulose from which it is derived, differing, indeed, only in being amorphous, and in being coloured blue by iodine. This substance, from its resemblance to starch, has been called amyloid. ”

“ Decay of Ligno-cellulose.—When a mass of ligno-cellulose (jute) is allowed to lie for a long period in a damp state, it undergoes resolution accompanied by structural disintegration. The soluble products of this change are acid bodies of the pectic class, and astringent substances closely resembling the tannins. In this decomposition also we have evidence of the plastic condition of the ligno-cellulose molecule, of the variety of its modes of resolution, according to the various directions in which it is attacked. ”

“ That which has been actually made into paper requires to be softened by boiling in water and {105} gentle breaking in an engine. It may be necessary to heat it for a short time in a weak solution of caustic soda. This may be done either in a breaker or in special tanks provided for the purpose. Paper which has been printed upon requires a rather more drastic treatment, and it must of course be used for an inferior quality of paper, as it is impossible to get it to as good a colour as the original pulp from which it was made—at least not economically. ”

“ In insisting upon the recognition of first principles, we cannot overrate the importance of a thorough grasp of the constitution of the plant fibres, as the necessary foundation for the intelligent conduct of paper-making, and to this subject we will at once proceed. ”

“ Many paper-makers add to the gelatine a certain quantity of soap, the effect of which is to render the paper capable of taking a high finish. The soaps employed should be white and firm, and should be free from rosin. Some soap-makers prepare a special soap for paper-making. They are usually made from tallow, or a mixture of this with a small quantity of coconut oil.
If a solution of soap be added to one of alum, a double decomposition immediately occurs, the fatty acid being thrown down in combination with the alumina, and the soda {164} combining with the sulphuric acid. ”

“ The aniline blues are soluble either in hot water or hot alcohol, the liquid being intensely coloured. Most of them are discharged by treatment either with strong acids or alkalis, the colour being restored by the reverse treatment.
Paper of any desired colour may be made either by using rags already dyed the necessary colour or by adding to the bleached pulp in the beater such dyes or pigments as will produce it. Any colouring matter which can be obtained in the form of a fine powder or as a solution can be used. Blue papers are usually coloured with ultramarine ”

“ Cuticular tissues, such as constitute the covering of fruits, are more simple in composition; the cuticle of the apple after purification, has the following percentage composition:
The cuticular substance of cotton, straw, esparto, &c., are doubtless similar bodies. These numbers point to a {27} remarkable similarity in composition to the fats, and, indeed, from the results of his study of this tissue, Frémy concluded that it was a fat in everything but its physical properties, of which we may mention insolubility in alcohol and in ether, and infusibility. ”

“ It is obvious that those materials, such as bleached cotton and linen threads and rags, which have already undergone treatment by the textile manufacturer, and are therefore more or less already in the state of pure cellulose, require but little chemical treatment at the hands of the paper-maker, whose attention is therefore chiefly directed to the removal of such adventitious matters as size, grease, &c. This can generally be effected by the employment of weak solutions of caustic soda, or even of lime at a low pressure. ”

“ H. J. Yaryan, of Toledo, Ohio, U.S.A., has been considerably developed in America in its several applications, and as we have authentic information of its successful working for the recovery of soda in some of the largest paper-mills in the States, we think it deserving of mention. The principle of the process is that of “multiple effects,” upon which, indeed, all the modern methods of economic evaporation are based. ”

“ If the chlorinated fibre be directly boiled with the sodium sulphite solution, its resolution into cellulose and soluble non-cellulose derivatives is complete: and this treatment constitutes the most simple and rapid method of estimating the cellulose in lignified tissues. It is only necessary finally to wash the cellulose with hot water containing a little acetic acid (when placed in a funnel it acts as its own filter) , and then with, alcohol, when it may be dried and weighed. ”

“ Owing to the fact that a considerable proportion of the pulp obtained from straw consists of cellular tissue (see Fig. 13, p. 58) , which, although cellulose, is devoid of fibrous structure, paper made from straw only is found to be much weaker than that made from fibres such as esparto. On the other hand, being a cheap material, and one capable of yielding a very white pulp with a moderate quantity of bleach, it is held in considerable repute by many paper-makers, especially as a material for mixing with esparto. ”

“ In isolating the bast fibres employed in the textile industries, a preliminary partial disintegration of the plant stem is brought about by the process of steeping or retting, by which the separation of fibre from flesh or cellular tissue is much facilitated. ”