wis PEND m™ eas #5 oe met Per’ aor, Pr “+ Si eS Ma EE OES CERS x) és Sata: cE) = v Tie wean 4 ney 45 vets ke 2 cm) if bees RPP ie See ear ay oe? i i 2: mes oe F Letasees ERB ope aS 3 ¥ ; ood THE UNIVERSITY OF ILLINOIS LIBRARY 66%.9 CBBsw ook Md ? “. i : } THE UNIVERSITY OF ILLINOIS LIBRARY 663.9 CBSw Overdue boo! a fine of 2 e AN rays TOE ary " tees ues tu de Bae A Ma a Se The “UWlestininster” Series WOODS PULP AND Ils UsEs WOOD PULP AND TES USES C. F. CROSS, E. J. BEVAN AND R. W. SINDALL WITH THE COLLABORATION OF Vie Ne eb A CON NEW YORK D. VAN ‘NOSTRAND CO TWENTY-FIVE PARK PLACE IQI4 10 JUN 14 bin MoOlurg. Ig 7 r Vhemiatry, 3de PREFACE Tue world has had its Stone age and its Bronze age: later its Iron age, and the present is a Cellulose age. This is not said ad captandum ; it is a statement which will survive critical examination. The volume now offered to students and the general public is based on studies in the domain of cellulose, -both theo- retical and scientific, and practical or industrial. It is not a monograph or a text-book of the subject: it does not pretend to be systematic or exhaustive. Technical literature in these days threatens to develop to formidable dimensions; and systematic works on branches of technology: necessarily carry a large weight of fact and information which is common groundwork. We have only given an outline of what appears essentis] as a cyclopedic framework. We are not addressing our- selves particularly to the specialist, nor to the technical student. Rather to the general reader, and our aim is therefore to give a general account of the evolution of the wood pulp industries, as typical of the age we live in, and as a very substantial contribution to its primary necessities. But if wood pulp has had an interesting past history, its 280019 vi PREFACE , future is suggestive of many more interesting possibilities of which we endeavour to give indications. From whatever standpoint in fact the subject is treated, if challenges attention. The chemist, the manufacturer, the political economist, and of course the financier will find that it teems with pro- blems the solution of which carries rewards of great moment. | In an age when pessimists see little but competitive exhaustion of sources of natural wealth, it is satisfactory to be able to present a domain still full of unexplored possi- bilities. Such is the subject of ‘“‘ wood pulp” or, more broadly, “cellulose,” and we trust this imperfect contribution will help to sustain and awaken the interest of readers and students. We have pleasure in acknowledging the valuable assistance of Mr. W. N. Bacon B.Sc., F.1.C., in contributing matter and revising proofs. We are indebted to the Royal Society for the privilege of reproducing illustrations from papers of the late W. J. Russell (p. 73). ‘lo Messrs. Longmans, for permission to reproduce portions of ‘‘ Researches on Cellulose,’ II. The illustrations in Chapter I. are chiefly from original histological studies of Messrs. Flatters, Muilborne and McKecnine (Longsight, Manchester), whose excellent work in this field is well known, or sheuld be, to all students of Botany. CHAP, Iit. CONTENTS THE STRUCTURAL ELEMENTS OF WOOD .. . I. CELLULOSE AS A CHEMICAL INDIVIDUAL AND TYPICAL COLLOID. Il. THE LIGNONE COM- PLEX, LIGNO-CELLULOSE ; SPECIAL CHEMICAL NOTE ON AUTOXIDATION, AND RESEARCHES OF W. J. RUSSELL . : : . . . WOOD PULPS IN RELATION TO SOURCES OF SUPPLY: FOREST TREES AND FORESTRY THE MANUFACTURE OF MECHANICAL WOOD PULP CHEMICAL WOOD PULP NEWS AND PRINTINGS WOOD PULP BOARDS THE UTILISATION OF WOOD WASTE. TESTING OF WOOD PULP FOR MOISTURE . WOOD PULP AND THE TEXTILE INDUSTRIES SPECIMEN PAGES—VARIOUS TYPES OF PAPER . BIBLIOGRAPHY . INDEX ° . . : . : : ° . PAGE FIG. SN) De Pi oieOE SIP EUStT RA PIONS TRANSVERSE SECTION OF STEM OF TRADESCANTIA SHOWING EPIDERMAL TISSUE, PARENCHYMA CON- TAINING STARCH, AT THE CENTRE A VASCULAR BUNDLE TRANSVERSE SECTION OF A YOUNG STEM OF PINUS SYLVESTRIS (COMMON PINE). BELOW, PRIMARY GROUND TISSUE FOLLOWED BY WOOD IN DEVELOP- MENT AND IN SUCCESSION CAMBIUM BAST AND CORTEX. IN THE CENTRE IS A MEDULLARY RAY . TRANSVERSE SECTION OF AN OLDER STEM OF PINUS SYLVESTRIS (COMMON PINE) SHOWING DEVELOP- ING BRANCH, A MORE ADVANCED WOOD SYSTEM AND EXTERNAL TO THE LATTER THE CAMBIUM AND PHLOEM TISSUES . LONGITUDINAL SECTION VASCULAR BUNDLE OF ZEA MAIS SHOWING SPIRAL, ANNULAR, AND PITTED VESSELS. SURROUNDING THE BUNDLE IS THE GROUND TISSUE OR PARENCHYMA : : : LONGITUDINAL SECTION OF STEM OF GOSSYPIUM S.P. (COTTON PLANT) SHOWING FROM LEFT TO RIGHT PITH, SPIRAL VESSELS, CAMBIUM, PHLOEM, COR- TICAL TISSUE, AND CUTICLE A TRANSVERSE SECTION OF STEM OF ZEA MAIS (INDIAN CORN). VASCULAR BUNDLES SURROUNDED BY PRIMARY GROUND TISSUE. EACH BUNDLE CONTAINS LARGE PITTED AND ANNULAR VESSELS WITH PHLOEM AND SCLERENCHYMA : L A PAGE ~l Y 10 me LIST OF ILLUSTRATIONS FIG. 5B. JUTE—SECTION OF BAST REGION SHOWING WEDGE- SHAPED BUNDLES EXTENDING FROM CAMBIUM TO CORTEX : ‘ : ! : : : 4 5C. JUTE (MAG. 300)—SECTION OF BAST REGION SHOWING STRUCTURE OF BUNDLES AND THICKENING OF ULTIMATE FIBRES 5D. FLAX—SECTION OF STEM OF LINUM SHOWING GROUPS OF BAST FIBRES LYING BETWEEN WOOD AND CORTEX ; 6. TRANSVERSE SECTION OF STEM OF LYMNANTHEMUM (AQUATIC PLANT). CENTRAL AXIS WITH XYLEM AND PHLOEM ELEMENTS. GROUND TISSUE SHOW- ING LARGE AIR CELLS PRODUCING BUOYANCY, AND STAR-SHAPED IDIOBLASTS | 7. TRANSVERSE LONGITUDINAL SECTION OF STEM OF TILIA EUROPQ@A (LIME TREE), SHOWING BAST FIBRES AND GROUND TISSUE 8. TANGENTIAL LONGITUDINAL SECTION THROUGH THE WOOD ELEMENTS OF TILIA EUROP@A (LIME TREE). FROM LEFT TO RIGHT A MEDULLARY RAY IS SEEN IN THE ROW OF LITTLE CELLS, FOLLOWED BY TYPICAL WOOD FIBRES, SPIRAL AND PITTED VES- SELS, AND CONNECTIVE TISSUE . ; ; : 9, LONGITUDINAL RADIAL SECTION OF PINUS SYLVESTRIS TIMBER SHOWING WELL-DEVELOPED BORDERED PITS UPON THE WALLS OF THE TRACIIEIDS. AT RIGHT ANGLES TO THE TRACHEIDS IS A MEDUL- LARY. avo. ; 5 10. TANGENTIAL LONGITUDINAL SECTION OF OLD WOOD OF PINUS SHOWING TRACHEIDS AND MEDULLARY RAYS; THE LATTER CONSIST OF TWO OR MORE ROWS OF CELLS ARRANGED LONGITUDINALLY PAGE if: 14 16 17 FIG, 11A. Lis. os RS LIST OF ILLUSTRATIONS TRANSVERSE SECTION OF STEM OF GOSSYPIUM (COTTON PLANT) SHOWING ONE ANNULAR RING OF XYLEM AND PHLOEM ELEMENTS WITH INTERVENING CAMBIUM LAYER. : TRANSVERSE SECTION OF A THREE-YEAR-OLD STEM OF TILIA (LIME TREE). AT CENTRE PITH THEN XYLEM (WOOD) IN THREE SEPARATE RINGS. TOWARDS THE PERIPHERY THE CAMBIUM RING THEN PHLOEM AND CORTICAL TISSUE... é DATE PALM. TYPICAL MONOCOTYLEDON PERENNIAL PINE. TYPICAL CONIFER. EXOGENOUS GYMNOSPERM. OAK. TYPICAL ANGIOSPERM EXOGENOUS PERENNIAL . LARCH . OAK . SPRUCE SCOTCH FIR ; : : ; : VIEW OF HORIZONTAL GRINDER (A), WITH SECTION (B) CURVE FOR ILLUSTRATING POWER TRIALS SHAKING SCREEN CENTRIFUGAL SCREEN FOR WOOD PULP SECTION OF CENTRIFUGAL SCREEN FOR WOOD PULP DIGESTOR FOR MANUFACTURE, OF BROWN PULP. TOWER BLEACHING PLANT HAAS AND OETTEL ELECTROLYSER CHLORINE CAUSTIC SODA CELL (SECTION) . THE ‘‘ HOLLANDER” BEATING ENGINE ND 238A. DIAGRAMS OF WEDGE SYSTEM SPINDLE FOR TWISTING PAPER-STRIPS MACHINE FOR ROLLING FLAT STRIPS OF PREPARED SHORT FIBRE (SLIVER) ° x1 PAGE 19 WOOD PULP AND ITS USES CHAPTER I THE STRUCTURAL ELEMENTS OF WooD THERE are no more interesting studies than those which group themselves under the term Applied Sciences. It is quite true that science, or rather the sciences, may be pursued from a point of view which ignores the services which they render to man; but whereas “pure science” is an ideal rather of the imaginative world, the natural prosecution of the sciences compels the recognition of their organic interdependence with human progress. Whichever aspect is the more attractive on general grounds, it is clear that the subject of this work is pro- minently typical of this. interdependence; involves in a particular manner the utilitarian bearings of science, and our treatment of it must be accordingly utilitarian. Wood pulp is a comparatively modern product called into existence as a paper maker’s raw material. The woods which furnish the product in its various forms have been impressed into the service of man from the earliest, in fact from prehistoric, times, and have been used for their structural qualities in a large number of our most important industries. The uses of the woods are so W.P. B 2 WOOD PULP AND ITS USES universally familiar that it would be superfluous to particularise them. We may, however, preface our specialisation to the par- ticular employment of certain woods as the basis of wood pulp, by calling attention to the physical and mechanical properties of a typical range of woods considered as structural materials. | For the natural history of the woods as products of vegetable life and growth we turn, of course, in the first instance to the science of Botany. In the scientific treat- ment of plant life questions of utility—that is, the part which a plant or any of its parts, seed, flower, stem or root, may play in the service of man—has no part. Moreover, external features are of quite subordinate moment. Thus the cereals which furnish, perhaps, the most important staple of our food are to the botanist no more important than any other of the great family of the grasses. It is not without significance to the botanist that these particular grasses have come to be selected and specialised by cultivation through countless generations, so as to ditferentiate them as economic products. But such con- siderations are relatively unimportant, as not concerned in those elements of identity and characterisation which fix the position of an individual plant in the scheme of botanical science. So also in regard to external features such as size, form, and vegetative habit. The sugar cane or bamboo are not obviously related to the cereals, but to the botanist the relationship is of the closest. The laburnum and the trefoil have little in common as regards form and life history, but they are blood relations. THE STRUCTURAL ELEMENTS OF WOOD 3 The relationships are fixed by the more fundamental features of the reproductive mechanism; both the major and minor differentiations constituting the basis of the classifications of botanical science are those of the repro- ductive system. These differences necessarily are corre- lated with those of the plant body, by which the second creat function or group of functions is conditioned, viz., those of nutrition. As the reproductive mechanism becomes more complex, so the structural type is differen- tiated towards complexity. Viewing the plant world as an evolutionary series, reproduction by seeds is the last feature to make its appearance, and is preceded by those differentiations of the plant body which issues in what is known as a vascular system. Thus in the fern the structural features of the higher flowering and seed-bearing plants are recognised, and in a tree fern the differentiation into vascular tissue, leaves and stems, with the lower portion formed into a root system, are apparent. But the reproduction of the fern is on a much lower plane, and it bears no seeds. The tree fern is a kind of pseudo-morph of the true tree or forest tree, which is a Spermatophyte or seed-bearing plant. Of the four great groups of modern botanical classifica- tion the spermatophytes are much the most conspicuous and widely distributed. Moreover, they are so interwoven with our experience that their study has often ranked as co-extensive with botanical science to the exclusion of the other great groups. These are the alge, the lichens, and the fungi(Thallophytes), the mosses (Bryophytes), and ferns, horsetails, and club mosses (Pteridophytes). The modern science regards these groups as related in evolutionary B 2 4 WOOD*PULR AND 2 TsaUisiis sequence. ‘There are two aspects of this evolution. The one involves the theory of descent, the higher from the lower order, as an objective fact; on the other the development of the highest type can be followed through the lower by the study of the dominant or reproductive functions, which thus unfolds itself as a homogeneous con- ception of the relations of the infinitely diversified forms of plant life. We are not concerned with these fundamental generalisa- tions further than to indicate their connection with our subject. We shall have to point out that from the point of view of “wood pulp” the trees which furnish these industrial products are of two sub-groups, and we have explained the basis of classification sufficiently to convey their relationship to the general reader in the terms employed by the botanist :— Spermatophytes (seed-bearing plants) be i er Gymnosperms Angiosperms (naked or exposed seeds) (enclosed seeds) Monocotyledons Dicotyledons (Conifer) Bamboo Poplar Pine Spruce Sugar Cane. We have already indicated that our subject has only an incidental connection with these fundamental relations. The plant is a structure, an agglomerate of structural elements; and its work as a plant is to grow, to build up tissue The assimilating organs of the higher flowering THE STRUCTURAL ELEMENTS OF WOOD 5) plants are the leaves. The leaf is the centre of the funda- mental operation of building up “organic”? compounds Fig. 1.—Transverse section of stem of Tradescantia showing epidermal tissue, parenchyma containing starch, at the centre a vascular bundle. from the inorganic form of carbon, viz., carbonic anhydride, contained in the air, and of which gaseous mixture it is a normal constituent. This characteristic function of the 6 WOOD PULP AND ITS USES plant, the photosynthesis of carbon compounds and their Fic. 2.—Transverse section of a young stem of Pinus Sylvestris (common pine). Below, primary ground tissue followed by wood in development and in succession cambium bast and cortex. In the centre is a medullary ray. elaboration to tissue material, we must take for granted ; as well as the complementary function of the root system THE STRUCTURAL ELEMENTS OF WOOD in absorbing water, inorganic mineral compounds, and other nutrient material from the soil. ¢ 4 ha ET Eades SSince 9 ip ko te etn, f, is ae Pe, ae ee oe ed ($3 hy Fic. 28.—Transverse section of an older stem of Pinus Sylvestris (common pine) showing developing branch, a more advanced wood system and external to the latter the cambium and phloem tissues. We are concerned with the plant as a completed struc- ture. The study of those functions and processes from which WOOD PULP AND ITS USES the structure results, and with which it is in its several parts associated, constitutes the branch of the science , : ay? #98 2 ¥ i | . eA ASE, nas f, p< gr et em - a i bai oe se here 3 ‘ cs find : rr¢ — ; ‘ teen SE ge Fk) re PAR ECAR SEs ‘ : : igas ‘¢ 2 HAL A ‘ 2 = - ee RCS GP ame da: ott a 5s eK ek : ito Estep ere om 5 EE oe ene N IR saoed ere se € rs A pee ae a0 se ee ne a = ne - 12s re = i paeciacsie “ OR Sie isis rn rt i i ne Aiea = eset = sat "5 pen a . : . es ees spiysit bee annular, b) iral gitudinal section vascular bundle of Zea e bundle is the 3.—Lon owin Mais sh FiG. and pitted vessels. Pp (eS th Surrounding parench ground tissue or yma. . 1re logy; and students who des a more comprehensive survey of the subject-matter are referred to the special text-books. Vs10 known as vegetable ph Ms THE STRUCTURAL ELEMENTS OF WOOD Taking the plant as a structure, we find it an assemblage Ree The typical cell is a a aw ae . asiseiie ‘ noo a aaa ne ees OR Me NEE ma AE i eee of units generally known as cells. ypium 8.P. (cotton plant) showing from left to right pith, spiral gitudinal section of stem of Goss vessels, cambium, phloem, cortical tissue, and cuticle. Fia. 4.—Lon spherical body of small dimensions—0°1 and 0°5 mm. 10 WOOD PULP AND ITS USES diameter—and consisting of an enveloping wall enclosing the cell contents. Fic. 5.—Transverse section of stem of Zea Mais (Indian corn). Vascular bundles surrounded by primary ground tissue. Hach bundle contains large pitted and annular vessels with phloem and sclerenchyma. Variations and differentiations of the typical form corre- spond with infinite diversity of functions and conditions. Typical forms of cellular tissue are represented in Figs, 1-2, THE STRUCTURAL ELEMENTS OF WOOD 11 More extreme variations lead to the structural forms classed as fibres and vessels. These are elongated cells, the length being a very large multiple of the diameter. In a general way “fibres ” may be regarded as the strengthening elements of plant structures, and are of relatively simple form. ‘ Vessels” are a = ZEON wee \ econ SAN Ash pw =a Jute. Fic. 58.—Section of bast region showing wedge-shaped bundles extending from cambium to cortex. the seat of complex vital functions and operations involved in nutrition, and are much more diversified in form. Typical fibres and vessels are represented in Figs. 3—4. The arrangement of cells, fibres, and vessels in the stem of a plant is co-ordinated with those characteristics which determine its position in the evolutionary series. We may 12 WOOD PULP AND ITS USES briefly describe stems which are typical of the two main divisions of the highest group of flowering plants. Fig. 5 represents a section of the stem of a mono- cotyledon. These structural types introduce the fundamental con- siderations involved in differentiation of tissues; ground Jute (mag. 300). IIc. 5c.—Section of bast region showing structure of bundles and thickening of ultimate fibres. tissue, known as parenchyma, is made up of thin naked cells showing equality in their dimensions, though occa- sionally elongated. The earliest differentiation of the eround tissue separates nutritive cells from reproductive cells : in the building up of the plant body we are concerned with the former only, and their further specialisation THE STRUCTURAL. ELEMENTS OF WOOD 13 is an adaptation to mechanical and physical exigencies rather than for vital purposes. The requirements to be met are (1) for the transportation of nutritive matter from the leaves where it is manufactured, as well as of water absorbed by the roots. Hence the provision of con- ducting tissue—or mestome; (2) the plant, to maintain Fic. 5p.—Section of stem of Linum showing groups of bast fibres lying between wood and cortex. its form, requires mechanical support, and tissue is differentiated into rigid structures known as stereome. These features are generally illustrated in the annexed figure, showing in section the stems of two dicotyledonous annuals, flax and jute, and of a monocotyledonous annual Indian corn (Zea Mais). 14 WOOD PULP AND ITS USES They will be better understood after dealing with the more complex case of the perennial stem. ‘The forma- tion of wood, 2.e., massive wood, is a process which is con- cerned with the growth of trees, and although the perennial erowth introduces no new structural elements, it does present a certain development of plan or arrangement Y ty ros ry + a a ae 3, e eos (he 4 f °, eB Yo Te, eee’ scare yy mI Yy S pense D 7 3 a 2 x 4 a i bd Na iveg eogea: ee "se es + 4 SOR x A YE at FS oo galas vet ae PEG eResroiics.. ae ae. StH beet By iw Be ves Fic. 6.—Transverse section of stem of Lymnanthemum (aquatic plant). Central axis with xylem and phloem elements. Ground tissue showing large air cells producing buoyancy, and star-shaped idio- blasts. beyond that of the annual stem. At the outset we notice there is a contrast of the dicotyl (or conifer) stem with the monocotyl, and since the supply of wood pulp is at this date exclusively drawn from wood of the former types, we must set out their typical characteristics in some detail. The apex of a growing stem exhibits an active condition 15 NTS OF WOOD \ stele, and between them (c) the cortex. THE STRUCTURAL ELEM of cell division with a differentiation into definite regions, (Lymnanthemum, Fig. 6.) which becomes more marked as we proceed downwards. (a) epidermis, the external protective tissue; (b) the central In the finally differentiated stem these are marked out as cylinder, or wei Maraer ht uf ! aN DEATH RAL aye: = = —e Y A + Beare R ; sat ] olWe =45! Hepes ; f ! aN a LE HN round O co) e bast fibres and howin eitudinal section of stem of Tila S ), Lime Tree Huropoea F ia. 7.—Transverse lon tissue. The cortex is complex In the perennial stem the epidermis does not keep pace with the increasing diameter, and the cortex becomes the external protective tissue known as cork, with its well- known impervious characteristics. in structure. 16 WOOD PULP AND ITS USES It contains active chlorophyllic and assimilating tissue, and cells which have a storage function ; also well-marked USERERSIS j ye Asi ¥ W Cit \ ; i vt e 41 + : | } bof ta A PY | 4 hc! mw os fe he bi os 7 i 4 poe ity iq ‘rag : i Ate} iY * —* 5 tee ! 23 ee - * fi Ma anne ee . = , <_tma Py dens # - > a - 4 - Ay i ae eas ee et ; = 4 : ae : 4 Yo = i rs Pee. - pe eS a —¥ ~ i ia a SELLE a Re ae gl : ; * anak « es, — vw ARS ithe ~~ Said ie — een eire RIFE Fie. 8.—-Tangential longitudinal section through the wood elements of Tila Huropoea (Lime tree). From left to right a medullary ray is seen in the row of little cells, followed by typical wood fibres, spiral and pitted vessels, and con- nective tissue. storage tissues known as collenchyma, or sheathing tissue, and sclerenchyma, or hard tissue. The latter is, from the THE STRUCTURAL ELEMENTS OF WOOD 17 present point of view, the more important, as it includes the elongated thick-walled cells known as fibres (Fig. 8). In the central cylinder, or stele, the vascular tissue is prominent (Fig. 7). There are two well-marked types of vessels—the trachez, which are of large diameter, with Fie. 9.—Longitudinal radial section of Pinus Sylvestris timber showing well-developed bordered pits upon the walls of the tracheids. At right angles to the tracheids is a medullary ray. heavy walls variously modified in structure into spiral bands, rings, or reticulations (Fig. 8). Being destined for water conduction, they are arranged end to end in a continuous longitudinal series. In the conifer stem there is very large characteristic development of the tracheal-like tissue ; but the constituent vessels differ W.P. C 18 WOOD PULP AND ITS USES from the true trachee in having tapering ends, and in not being disposed in longitudinal series. These vessels are called tracheids, and they are charac- terised by pitted walls which, under the microscope, appear as double concentric rings arranged in rows (Figs. 9 and 10). The second type of vessel is the sieve tube, so called q |) 4 Fic. 10.—Tangential longitudinal section of old wood of Pinus showing tracheids and medullary rays; the latter consist of two or more rows of cells arranged longitudinally. from the specially perforated area which they develop, termed the callus plate. They are concerned in the con- duction and distribution of organic nutrient matter. These two types of vessels are characteristic respectively of the xylem or wood, and phloem or bast. In the dicotyledonous stem the strands of xylem and phloem, THE STRUCTURAL ELEMENTS OF WOOD LY though separate, are organised together into vascular bundles. The disposition and relation of these bundles are the characteristic of the exogenous stem. They form a centric system—the xylem towards the centre, the phloem towards the periphery. The paren- chyma enclosed in the vascular cylinder is the pith or a Pe Fie. 114.—Transverse section of stem of Gossy- pium (cotton plant) showing one annular ring of xylem and phloem elements with intervening cambium layer. medulla, and its extensions outwards between the vascular bundles are called pith or medullary rays, and act as storage cells for reserve food material. But the most obvious feature of the transverse section of a forest tree, viz., the annual rings, remains to be elucidated. In the xylem-phloem bundles there is a central portion ; C2 20 WOOD PULP AND ITS USES of meristematic tissue, which continues the process of cell division and differentiation, contributing new xylem on the one side and phloem on the other. And further, this active tissue, known as cambium, extends from bundle to bundle across the pith (rays), assuming therefore a structural ring. The annual accretion of new tissue, which is a product of the cambium, is thus marked as ina ring. (Fig. 114.) As the trunk or stem increases in girth, an increasing portion of the xylem ceases to take part in the conduction of water, the ascending sap passes through the younger tissues or sap wood, which becomes differentiated in colour and other aspects from the heart wood; in fact, it is this differentiation of the sap wood from the heart wood by the formation of vessels, tracheids, and fibres of larger diameter and thinner wallsin the former tissues, that serves to accentuate the well-marked characters of the rings. (Fig. 11s.) The concentricity of the rings varies also in different trees; the gymnosperms, for example, are ex- tremely regular, whilst in some angiosperms the rings are more or less wavy, and in others again, such as the beech, the rings are crested. The new phloem deposited in contact with the old, causes rupture of the latter, and it pulls or scales away more or less rapidly. The bark of trees is very complex in structure, very variable in character both as regards its structural com- ponents and its proportion and massive distribution; generally it is not permanently associated with the stem or trunk, as are the new wood tissues. ‘This is also in accord- ance with our superficial observations of the habits of trees. The conspicuous feature of the dicotyledonous stem is, THE STRUCTURAL ELEMENTS OF WOOD 21 therefore, the collateral vascular bundle, open in the sense that the cambium constitutes a connecting tissue linking wat iuoaues F mee PLATA ais Tie ra Cate PS 6 oe * a. oe EF 8. a @ = Ita. 118.—Transverse section of a three-year-old stem of Tilia (Lime Tree). At centre pith then xylem (wood) in three separate rings. Towards the periphery the cambium ring then phloem and cortical tissue. . the bundles. In contrast with this, the monocotyledonous stem is composed essentially of a ground tissue, and . 22 WOOD PULP AND ITS USES scattered but closed fibro-vascular bundles, i.e., with no connecting cambium (see Fig. 5). This arrangement implies an absence of provision for large increase of diameter, and the stem of a perennial of this type is columnar or cylindrical rather than conical. There is a corresponding lack of provision for developing an increase of foliage by way of a system of branches. The foliage is thus a crown of leaves, as in the palm iG. 12.—Date Palm. Typical Monocotyledon Perennial. (Fig. 12), which remains very much the same from year to year. (Compare with Figs. 128, 120.) The vascular bundles generally develop stereome tissue, 7.e., sclerenchy- matous thick-walled fibres which, in association with the vessels, constitute the fibres and vascular bundles. We have now become aware of the principal structural elements of a wooded stem, and we can analyse some of the aspects of wood sections which are familiar to us as the “ grain.” | THE STRUCTURAL ELEMENTS OF WOOD 23 Usually the xylem elements are parallel to the axis, in which case we have the term “straight grain’; but irregularities appear in the growth of the various tissues Fic. 128.—Pine. Typical Conifer. Exogenous Gymnosperm. (1) by a continuation of the growth of the cells after separa- tion from the cambium proper, thus causing an interlacing of the fibrous elements, with a consequent cross-grain 24 WOOD PULP AND ITS USES effect ; or (2) in the formation of branches and adventitious buds, producing the effect known as ‘burr.’ Other irregularities are seen in the projections of the xylem Fig. 12c.—Oak. Typical Angiosperm Exogenous Perennial. elements from the rings, causing the ‘‘ bird’s-eye ”’ effect so well marked in the maple. In the angiosperms the medullary rays are much more THE STRUCTURAL ELEMENTS OF WOOD 25 highly developed than in the gymnosperms, and constitute in some cases a large percentage of the wood. In the oak the primary medullary rays may be built up of several hundred rows of cells, and when seen in radial sections appear as silvery bands, or silver grain, as it is termed. Some of the poplars frequently have the medullary system aggregated together in spots known as ‘“ pith flecks,’ which help to identify the species. We may note that in addition to the formation of the ligno-cellulose or primary plant substance (see p. 57), various other products of secretion are formed. Proteins, or nitro- genous bodies, carbohydrates, glucosides, resins, and other aromatic substances, acids, such as tannic acid, dye stuffs, which impart particular characters to the woods, and aid in its identification. PuysicaL Properties oF Woops. Weight.—This depends upon the condition of the wood in relation to moisture, and as regards structure, i.c., upon the proportion of small heavily lignified vessels such as would be illustrated by the ‘‘ heart wood,” this being relatively much more dense than the more distended vessels of the “ sap wood.” The following table illustrates the density of various woods :— Wood. Density. Very light Poplar 0°26 0°4 Light Spruce and Pine 0°4 0°6 Moderately heavy Birch and Beech 0°6 Wea Heavy Oak 0°8 and upwards 26 WOOD PULP AND ITS-USES Hardness.—This is usually measured in terms of the number of kilograms required to force a punch of 1 sq. em. in area to a depth of 1°27 mm. into the wood, perpen- dicular to the direction of the fibres. The following table illustrates the relative hardness in decreasing proportions :— Hardness in Wood. kilograms per sq. cm. Lignum Vite . 793 Oak : : ; : : : 225 Beech . ; 200 Most coniferous woods. ; 100 Cotton tree Bombax Malabaricum — - — (type of softest wood) Strength of Woods.—This may be defined as the resistance offered by the wood to any force tending to break the fibres across (transverse stress), or to overcome the cohesion of the fibres (longitudinal stress). In the testing of woods various other stresses are applied; but the breaking strain, as stated above, is by far the most important. It is found that in broad-leaved trees the lateral resistance is from 2th to 4th of the longitudinal resistance, and in the coniferous 35th to ;4th. Tetmayer of Zurich has arranged in the following table the relative resistance of the woods to various stresses :— Transverse Pressure. Tension, Crushing. Shearing. Beech Beech Oak Beech Oak Oak Beech Oak. PHYSICAL PROPERTIES OF WOODS 2 ~I Transverse Pressure. Tension. Crushing. Shearing. Larch Scotch Pine Larch Larch _ Silver Fir Larch Silver Fir Spruce Spruce Spruce Spruce Silver Fir Scotch Pine Silver Fir Scotch Pine Scotch Pine. It was found that Scotch pine had the lowest technical value, silver fir 20 per cent. greater, spruce 26 per cent. creater, larch 66 per cent. greater, oak beech 95 per cent. greater. Two other factors usually determined in wood are (1) the ash, that is the amount of inorganic constituents left after burning the wood, which is a small proportion by weight though voluminous ; (2) the calorific, or fuel, value of the wood. On an average it is found to be about 4,000 calories or heat units, in other words, one unit of weight of dry wood on burning furnishes heat which would raise 4,000 units of weight of water 1° C. The foregoing brief exposé implies the fundamental con- ditions of fitness of a given wood or wood substance for conversion into a fibrous raw material. These are primarily a large proportion of elongated cells or fibre, and, as the basis of economic production of such pulps, it will be obvious that the massive perennial stem fulfils essential industrial conditions of growth, transport, and treatment for conversion into pulp, which result in low cost of production. The processes of pulping to be dealt with in a subsequent chapter, are of two kinds: (1) a simple disintegration by wet-grinding, toa ‘‘ mechanical” pulp. Such pulps are sub- stantially the original wood substance, deprived incidentally 28 WOOD PULP AND ITS USES of water-soluble constituents (see p. 97); (2) chemical processes which attack the igneous constituents and convert them into soluble derivatives, leaving the cellulose which preserves the form and dimensions of the original fibres constituting a ‘‘ chemical” pulp composed of the fibrous structural elements of the wood in the fully resolved condition (see p. 120). The number of woods fulfilling what is a very exacting specification of requirements, is extremely limited. Actually the wood pulp industry is based upon the utilisation of coniferous woods and poplar. CHAPTER II I. CELLULOSE AS A CHEMICAL INDIVIDUAL AND TYPICAL COLLOID. II. THE LIGNONE COMPLEX, LIGNO-CELLULOSE; SPECIAL CHEMICAL NOTE ON AUTOXIDATION, AND RESEARCHES OF W. J. RUSSELL THE investigation of the nature and composition of the woods is a problem of “ organic chemistry.’ The wood substance is in all cases a complex of carbon compounds. The woods present variations in composition which are definite and characteristic; but these are only minor divergences from a common type. As representative of the type we may take two individuals. The jute fibre—the lignified bast fibre of an annual, a simple tissue—and beech-wood, which represents perennial growth, and from its nature is an assemblage or mixture of structural elements. We have in the previous chapter spoken of “‘ lignification ” as a process. Morphologically it is a process of thickening by incrustation, and according to recent researches this incrustation is a process of forming adsorption com- pounds, the colloidal hydrated celluloses first elaborated, taking up soluble colloidal products from solution in the cambium fluids or “ sap’’ (A. Wislicenus, Zeitsch. Kolloide, 1910, p.17); chemically it is regarded as the formation ofa cellulose derivative by combination of cellulose with certain acid and unsaturated ketonic groups, the resulting 30 WOOD PULP AND ITS USES compound or complex being a ligno-cellulose. Conversely, by various processes which attack these acid and unsaturated groups, the ligno-cellulose is resolved into derivatives of the latter which are soluble, and cellulose which is resistant and insoluble. ‘The separation or isolation of cellulose is attended by disintegration; the aggregated structure is resolved into its component units, which are cells, including in this general term fibres and vessels. In the ligno- celluloses these are of small dimensions, 2—38 mm. in length, and ‘02—-03 diameter. A mass of such units in contact with water constitutes a ‘‘ pulp.” The separated cells retain their dimensions and general structural characteristics notwithstanding that the elimination of the non-cellulose components is attended by considerable loss of substance, z.e., weight, and the cellulose may therefore be regarded as the more permanent skeleton or framework of the cell. The quantitative relations of this resolution are of importance. The following percentage numbers characterise the typical ligno-celluloses :— Cellulose. Lignone. Jute . : : (050 pe : 30—20 Beechwood ‘ 50—60 . . 50—40 It may assist the student in estimating the practical significance of these chemical facts to point out that a ligno-cellulose is related to cellulose somewhat in the same way asan alloy of gold with baser metalsis to gold. Goldas a “noble metal’ is relatively non-reactive, and especially distinguished by resistance to oxygen, and is therefore permanent in the air and generally unaffected by the conditions which prevail on the earth’s surface. Cellulose CELLULOSE AS A CHEMICAL INDIVIDUAL 31 is resistant to oxygen and water, and is permanent under the prevailing conditions of our planet. A gold alloy is amenable to the attack of oxygen which combines with the constituent metals, converting them into oxides, or of reagents which dissolve the baser metals as salts: the gold is left as elementary metal. Similarly, cellulose is obtained as aresidue resisting the action of reagents such as chlorine, caustic alkalis or bisulphites, all of which combine directly with the lignone groups, for reasons which will appear. It would take us outside the scope of our present treat- ment of the subject to attempt an exhaustive exposé of the chemistry of these natural products. The special outline which we give may be regarded as the irreducible minimum necessary as the foundation of the chemical technology of the subject. We have already implied that the woods are modified celluloses, from which their more important constituent, that is the cellulose, is readily isolated. Cellulose is a carbohydrate ; it 1s derived from the sugars and under severe treatment may be resolved into sugars. Its ultimate composition is represented by the formula n(CgHi0s), and, in breaking down to the simplest sugar, CgH120¢ the process may be formulated as one of simple “hydrolysis”: n(CgHi005) + nH2O = nCegHi20¢. But of the mechanism of this resolution we are profoundly ignorant. Indeed, it cannot be said that the above equation of hydrolysis has been verified experimentally. Recent researches of H. Ost and L. Wilkening (Chem. Zeit., 1910, 34, 461), establish a conversion of cellulose into fermentable sugars to the extent of 90 per cent. of its weight, with a residue of acid products. The above equation 32 WOOD PULP AND -ITS USES is therefore not more than an approximate picture of the underlying facts. This is equivalent to the statement that we are entirely ignorant of the actual constitution of cellulose. We are more familiar with another complex carbohydrate, starch, which has a similar empirical formula n(CgHy00s). Starch is quantitatively resolved into the sugars, maltose and dextrose, by hydrolytic action determined by reagents or by ferment actions and under conditions which enable us to follow minutely the stages of the transformation. These reveal the extreme complexity of the aggregate which constitutes starch. But although we can closely follow this chemical disintegration through its stages, we are unable to integrate these results of analysis into a formula, still less by any laboratory process to reascend the scale and trans- form the products of resolution back to starch. A fortiori, the proximate constitution of cellulose is problematical. Starch and cellulose are not only closely linked by many analogies which have been established by comparative investigation in the laboratory, but in the plant they stand in intimate, in fact genetic, relationship, as evidenced by the transformation from one to another, and the equivalence of their vital functions in many respects. Premising these relationships, we may state that the ultimate component sroups of cellulose are those of the carbohydrates generally and of the sugars in particular—ie., saturated compounds and derivatives of polyhydric aleohols—generally resistant .e., non-reactive. But the special chemistry of cellulose has to do with the complex or aggregate. ~The particular feature of cellulose is that it enters into a number of reactions, combining with other bodies to form highly CELLULOSE AS A CHEMICAL INDIVIDUAL 30 characteristic derivatives, in which the essential properties of the aggregate are fully maintained. These properties are recognised in the following: (a) the colloidal character- istics of the solutions of the original cellulose, as of its ethereal derivatives; (b) the structural characteristics of the solids obtainable from these solutions by elimination of the solvent; (c) the weight relations of the products, the cellulose maintaining its integrity as a complex. What we have to set forth as a sketch of the special properties of cellulose will follow this order of, idea. rh Cellulose as a Typical Colloid.—lt may be said generally that we know very little of solid substances; it is only in solution or the fluid state that matter lends itself to quanti- tative analytical investigation. It is in the manifestation of associated properties in solution that compound matter has come to be regarded as falling into two great divisions, Crystalloids and Colloids. Crystalloids are crystalline as solids and when dissolved in neutral solvents constitute limpid solutions; Colloids are non-crystalline or amorphous, and dissolve to viscous or gelatinous solutions. On evapo- rating the solvent the former resume their crystalline form, the latter constitute structureless masses; these may be transparent, and if spread over a relatively large superficial area they take the form of a film or sheet. A familiar type of colloid is gelatin. Gelatin in 10—20 per cent. aqueous solution at temperatures of 50—100°, is a viscous liquid ; the solution on cooling to 20—30° solidifies to a jelly or ‘“oel.” The “ gel” continues to lose water at its surface and, by withdrawing water from the interior, continues the process-of desiccation. The “air dry ”’ solid finally retains W.P. D 34 WOOD PULP AND ITS USES 15 per cent. of its weight of moisture, which requires a higher temperature for its expulsion. The dry solid is relatively inelastic or brittle. There are various views current as to the causes under- lying these phenomena. Any such view or “theory of the colloidal state’ must set out from the observed experimental facts which are, chiefly: (1) The antithesis between solid crystalline and amorphous matter; (2) the correlatively divergent properties of these two types of matter when in solution: thus, the crystalloids are generally electrolytes : they are conductors of the electric current, by which they are readily decomposed, taking up the electrical energy and splitting into polar constituents ; the colloids are non-con- ductors in this sense. The crystalloids are diffusible, 1.e., they readily pass through membranes such as parchment, or parchmentised paper—the phenomena being classified under the term osmosis ; the colloids are not diffusible— that is, exert no osmotic pressure in solution—and conse- quently are not transmitted through such membranes or films. The crystalloids, in dissolving, undergo changes of volume, accompanied by considerable thermal effects: the colloids dissolve with relatively sight volume change. Colloidal matter, when observed in transparent forms, is optically homogeneous ; crystalline matter exhibits selective actions which are classified under the term polarisation. These effects in certain groups of compounds, e.g., the sugars, persist in their solutions. It is important to note that we have the primary antithesis of solid form, associated with differentiated relationships to the various forms of energy— electricity, heat‘and hght. It must not be assumed, how- ever, that there is any sharp distinction of one form of CELLULOSE AS A CHEMICAL INDIVIDUAL 35 matter from another: the antithesis is an opposition of extremes, emphasised by the comparison of typical repre- sentatives. But these extremes graduate on either side into forms of matter which have the characteristics of both. There is an important deduction from these relationships, which is that throughout the series the ultimate properties of matter are involved as the conditioning factor of the “physical” state. It was formerly held that the antithesis of crystalloid and colloid was of “‘ physical”’ significance only, that is, depended rather upon proximate relationships than upon the ultimate properties of matter, which are ‘chemical.’ We cannot pursue this theme at any length, and we must refer students who aim at more fundamental analysis of phenomena to special treatises, instancing more particularly ‘‘ Neue Gesichtspunkte zur Theorie der Kol- loide”’ (EK. Jordis, Erlangen, 1904), and other critical and experimental contributions which connect the properties of colloids with the modern theory of solutions. As a general text book we need only mention “ Grundriss der Kolloid- chemie,” by W. Ostwald (Dresden, T. Steinkopff). For a general résumé of the literature of colloids covering the earlier periods, the ‘‘ Bibliographie der Kolloide,” by A. Muller (Leipzig, 1904, L. Voss), and for present develop- ments the scientific serial ‘‘ Zeitschrift fiir Chemie und Industrie der Kolloide”’ (Dresden, Steinkopff). As a general review of the chemistry of cellulose considered as a typical colloid and tlie probable relationships of its colloidal characteristics to chemical constitution, the student may consult ‘‘ Researches on Cellulose,”’ IT. (1906), Cross and Bevan. Cellulose is itself insoluble in all neutral solvent liquids. D 2 36 WOOD PULP AND ITS USES ¢ The ‘solutions of cellulose’ are in all cases solutions of derivatives. There are two main groups of these deriva- tives :— (a.) Colloidal double salts of cellulose with metallic saline compounds, viz., zinc chloride and cuprammonium. A “solution of cellulose’? results from digestion with these reagents in aqueous solution, and the cellulose is separated from. these solutions by mere dilution. It is obtained in a gelatinous, hydrated, and of course, structureless form. The precipitated cellulose retains the metallic oxides; but these are readily removed by treatment with acids. The solutions have a high viscosity and the limit of fluidity, for the purpose of the practical applications of these solutions is reached when the percentage of cellulose in solution is 5—7. Higher percentages in fluid solution are attained at the expense of the integrity of the cellulose aggregate, that is, by various processes of hydrolysis; thus, by employing with the zine chloride various and increasing proportions of hydrochloric acid, or by previous treatment of the cellulose with both acid and basic reagents, which resolve the aggregate by hydrolytic actions. It must be noted that the state of disintegration of the aggregate persists in the reverted product; the cellulose recovered from the solutions by precipitation is more or less degraded in its structural properties. (b.) The esters of cellulose are the derivatives which result from the combination of its OH groups with acid radicals. The most important of these are the Nitrates, or 30-called Nitrocelluloses, the Acetates and Benzoates. The Benzoates are of no practical (2.e., industrial) importance. The Nitrates and Acetates are formed by the action of the CELLULOSE AS A CHEMICAL INDIVIDUAL 37 acids or their anhydrides upon cellulose. The “ nitration ”’ > or “acetylation”? is progressive, and to form derivatives soluble in various neutral liquids the degree of esterification must proceed beyond a certain limit, viz., that represented by the combination of two of the OH groups of the unit CgHwO05. Actually the derivatives most commonly employed are, in the case of the nitrates, the esters intermediate between the dinitrate and trinitrate; in the case of the acetates, the complete solubility of the ester requires a stage of esterification closely approximating to the produc- tion of a triacetate. The solvents employed are in the case of the nitrates, ether-alcohol, alcohol and camphor, ethyl-acetate, ace- tone, and variations of these. The acetates are soluble in a more limited range of liquids, of which chloroform is the most important and characteristic; other solvents are acetic acid, phenol, and pyridine. It is important to note that these esters are produced with a necessarily large increase of weight of the product as compared with the original cellulose, resulting from the introduction of the relatively heavy acid or negative group. ‘This will be appreciated from inspection of the equations representing the limiting reactions thus :— Cellulose. Nitric Acid. Water. Cellulose Trinitrate. Ce Hi00; + 3 HNOs = 3 H.O + CelH,O2 (NOs) 162 (3 x 68) (3 x 18) 297 Cellulose. Acetic Acid. Cellulose Triacetate. CgHi190; + 3 C.H40. — 3 H,O + CeHOs (CgH302) 162 (3 x 60) (3 x 18) 288 38 WOOD PULPOAND “ITs USES an increase of weight in either case of over 75 per 100 of cellulose. These combinations, involving such large increases of weight, may take place under regulated conditions, without affecting the structural integrity of the fibre; the esters differing but little in external appearance from the original cellulose. They now dissolve in their respective solvents to structureless solutions, which are fluid at concentrations of 10—15 per cent. of the ester. It is to be noted from the weight relationship above set forth that these concentrations are in their equivalent of cellulose 6—8 per cent. From these solutions the esters are recovered unchanged, by evaporation of the solvent, or by removing it by the action of a liquid, which mixes with the solvent but is not a solvent of the cellulose. From the esters so recovered, the cellulose can only be regenerated by the chemical process of saponification, that is, by the attack of certain alkaline agents which combine with and remove the combined acid eroups and restore the OH groups of the original cellulose. In the industrial uses of these compounds they are sometimes employed as such, or as in the production of artificial silk, the solution being drawn or spun through fine orifices and solidified to the artificial thread which in the case of the nitrate is then denitrated or saponified to cellulose. The industrial process is therefore in the latter case a complete chemical cycle; the ester stage being, for all practical purposes, merely a solvent-plastic condition of the cellulose. (c.) Intermediate between these two groups and combining s CELLULOSE AS A CHEMICAL INDIVIDUAL 39 their essential features, is the derivative known as the sulpho-carbonate, or in solution, as viscose. ‘This is a water-soluble ester of cellulose, formed by treating cellulose with strong solutions of the alkaline hydrates, e.g., caustic ‘soda, and the compound so obtained, or alkali-cellulose with carbon bi-sulphide. ‘The ester is thus synthesised in the two stages, and its final form is the sodium salt of cellulose- xanthogenic acid, a compound freely soluble in water. The aqueous solutions of these derivatives (viscose) are structureless, and at cellulose concentrations of 8—12 per cent., are sufficiently fluid for manipulation through filters and for passage through fine orifices under small pressures. (See p. 247.) The reaction which produces these compounds is a reversible one, and the solutions, on standing, spontaneously revert to cellulose by dissociation of the alkaline sulphur residues. ‘The cycle of synthesis and decomposition may be represented by the subjoined diagram :— Synthesis. Alkaline hydrate Solution of -—_)y Xanthogenic Hster. 4 Carbon Bisulphide | 430% _ Viscose. oe goon yee -Carbon-disulphide ' Alkali and products of and Cellulose (Hydrate) interaction Cellulose Upon these fundamental facts are based a number of important industrial applications of cellulose. 40) WOOD PULP AND ITS USES In the preceding section we have indicated that the cellulose in the form of these soluble derivatives is a structureless colloid. In the plastic condition it may be made to take any desired form, and it is produced indus- trially in filament or thread, in film or sheet, or, lastly, in massive solids of any required dimensions. ‘The special feature of these artificial forms is a particular continuity of substance. In passing from the state of solution to the ultimate solid form there are no breaks in this continuity, and the structural characteristics of these artificial forms are conditioned by this fact, which, in turn, rests upon the ultimate constitution of the cellulose substance or matter. This finally must be held to be intimately associated with its typically colloidal properties. The practical effects or consequences of these constitu- tional properties are seen in the qualities of resistance of the derivative solids. The mechanical properties of the artificial threads, which are expressed in terms of tensile strength or tenacity, extensibility (elasticity), are essential factors of their textile applications. These properties are compared and brought to numerical expression in various ways: thus the tenacity 1s measured in terms of the maximum weight which the thread will support. As an average figure we may take this as 8,000—9,000 grms. per square millimetre of section. Another mode of expression of the physical fact is in terms of ‘‘ breaking length,” that is, the length of the particular fabric repre- senting such breaking weight. Elasticity is the maximum elongation of the thread under strain from which it will revert to its original dimensions when the strain is removed. This may be 2 to 8 per cent. Extensibility is CELLULOSE AS A CHEMICAL INDIVIDUAL 41 the elongation of the thread when strained to its breaking point. This varies from 10 to 20 percent.t These cellulose threads are known as “ artificial silks,’ and it is evident from the term, that they are applied to similar purposes as the natural silks. It is of interest, therefore, to compare these products in regard to their fundamental mechanical properties. We quote from a paper on ‘‘CelHulose and Chemical Industry’ (Cross and Bevan, Jowrn. Soc. Chem. Ind., 27, 1908). The comparison with silk is direct and simple, since both represent amorphous colloidal matter or substance. The artificial silks may be taken as showing the following range of textile quality :— Gramme. 2 Breaking strain or tenacity per unit denier. 1-0—1°4 Extensibility under breaking strain } : 159% == 17% True elasticity . ; : ; : : 4% —5% The corresponding averages for the true silks (in the boiled-off state) are :— Breaking strain or tenacity perdenier : 2°0—2°5 Extensibility under breaking strain . ; 15%—25% True elasticity . ; : : ; 4%—5% Strehlenert has established the following relationships, which are important (Chem.-Zeit., 1901, p. 1100). The breaking lengths are expressed in terms of kilo- erammes per square millimetre of section, which is a ' These points are further elucidated in Chap. X. 2 Denier is the unit weight/length : mgr. per 10 metres. 42 WOOD PULP AND ITS USES satisfactory basis of comparison in view of the close structural similarity of the products investigated :— Dry Wet. China raw silk P ; : : : 53°2 46°7 Hrench., 4; : : ‘ : : 50°4 40°9 “Natural var bolledrol ; : ; $ 25°5 13°6 “cake oy fo dyedired, weighted ae 20°0 15°6 silk. ,, blue black at 110 per cent. : 1294 80 5 Ss =) 140 per cent. mee iS, 6°3 ¥ 4h a 500 per cent. ; pb — *¢ Artificial ( Chardonnet wi rates : 14°7 La silks.” Lehner nas aaa Lea 4:3 Lustra Glanzstoff, cuprammonium process : 19°1 3°2 celluloses \ Viscose, xanthate process : : : Bina 673 The lustra celluloses are thus inferior in tenacity to the silks, but when these are ‘“ weighted” there is a loss of strength beyond that which would be directly proportional to the degree of ‘‘dilution” of the silk substance. As the weighting of silks is very largely practised, it will be seen that the lustra celluloses are quite on the average level of textile quality, even in this higher sphere. In regard to elasticity and extensibility, which are important correlative measures of textile quality, a similar series of relations obtains. The lustra celluloses, on the other hand, have a special relationship to water, the colloidal cellulose having a con- siderable hydration capacity. In actual practice this fact is not of such moment as to impede the very rapid progress of the industry in these new textiles. That this property or relationship of the cellulose is modifiable appears to be a reasonable deduction from the CELLULOSE AS A CHEMICAL INDIVIDUAL 43 general reactivity of cellulose. It has been presumed by investigators that the cellulose (hydrate) is susceptible of modification, either by intrinsic or constitutional change, or by reaction to form a new derivative, in such a way as to yield a product more nearly resembling the normal cotton cellulose in resistance to hydration. At this date there is only one method which has given promise of industrial results in this desirable direction. The cellulose, notably in the form of artificial silk, is treated with formaldehyde in aqueous solution containing also auxiliary agents determining combination. As a result of the combination it appears there is some constitutional change in the cellulose itself accompanying the fixation of the H,CO groups, and this suggestion 1s of moment, as it indicates a capacity of internal structural modification which offers an attractive field for research. It is of particular interest to note that the artificial silks, though produced by treatments of cellulose presenting the widest contrasts in chemical and physical conditions, are closely similar in their properties. It is evident from this that though cellulose is, in chemical language, extremely labile, it is nevertheless so constituted as an aggregate as to be equally stable, or resistant to change. The reversion of cellulose or of its esters from the solutions above enumerated, in the form of film or sheet, introduces no novel features of the product. ‘The qualities of the film which condition its industrial employment are tensile strength and elasticity. In the production of solids in massive forms, a number of factors are introduced with the exaggeration of the third dimension, and only one of the solutions, viz., viscose, 44 WOOD PULP AND ITS USES lends itself to the production of cellulose products of this order. The nitrate solutions which are the basis of the highly important celluloid industry area plastic form of the nitrate or cellulose ester, and the forms into which it is fashioned while in the plastic state are but little different in dimensions from those of the permanent and rigid solids into which they pass by evaporation of the solvent. These are constituted of the unchanged nitrate or cellulose ester. No economical method has been devised for turning out the acid groups from the ester in these massive forms and thus arriving at cellulose in corresponding forms. But the viscose solutions in spontaneously reverting to cellulose and solidifying may be cast, at this stage, into any desired form. ‘The masses so obtained are composed of the cellulose in a much hydrated state ; but though retaining nine times its weight of water (of hydration) it has, nevertheless, a con- siderable mechanical resistance. Permeated as it is with the alkaline-sulphur by-products, it requires exhaustive washing to remove them. ‘The purified mass of hydrated cellulose, if now dehydrated and desiccated by exposure to the atmosphere, parts with its water continuously and progressively, shrinks upon itself, and finally, is obtained in transparent or translucent masses. The cellulose solid so obtained is an extremely resistant material. The properties of this material may be compared with those of other solids used in construction, and it will be seen to have qualities of a very high order. Lastly, we have to call particular attention to the facts which have been generally noted as regards the weight relationships of these cycles of transformations. Taking the two extreme cases, that is, with the widest CELLULOSE AS A CHEMICAL INDIVIDUAL 45 divergence of the conditions of reaction and with reference to the same unit of cellulose, which we may conveniently take at 100 parts by weight: Cyclea. Cellulose. Nitrate. Cellulose (hydrate) Acid. One hundred parts of cellulose combine with nitric acid (with elimination of water) becoming 165 parts of cellulose nitrate, dissolved in alcohol-ether to 15 per cent. solution (equivalent to 9 per cent. cellulose) and spun to thread, denitrated with ammonium-magnesium sulphydrate, and reverting to 103 parts by weight of cellulose hydrate. Cycle 6. Cellulose. Xanthogenic Ester. Cellulose hydrate. Alkaline. One hundred parts of cellulose combine with 50 parts sodium hydrate (in presence of water), the alkali ceilu- lose reacts with 50 parts disulphide, giving 130 parts of cellulose-xanthate of soda dissolved to 13 per cent. solution, equivalent to 10 per cent. cellulose, drawn or spun into ‘setting ’’ solutions (see p. 246), which decompose the ester and regenerate cellulose, yielding 103 parts by weight of cellulose (hydrate). In either case, therefore, the cycle is completed without loss of substance by the cellulose: there is a slight gain due to combination with water. This is only strictly true of the normal cellulose, which is represented by the fully purified cotton fibre. Other celluloses, notably wood-celluloses, sustain a loss of weight due to conversion into permanently soluble derivatives, which may amount to 10—20 per cent. Reciprocally, the 46 WOOD PULP AND ITS USES viscose cycle becomes a constitutional criterion, a normal cellulose being one which sustains this cycle of reactions of synthesis and decomposition without loss of substance. These experimental facts define cellulose as a typical colloid. It has, of course, long been recognised in general terms that cellulose in its “‘ organic’ forms must be classi- fied as a colloid. But the colloidal state having become a definite objective of investigation, it is evident that the investigation of cellulose through its compounds and deri- vatives is destined to contribute considerably to the develop- ment of the general theory of the colloidal state. For this reason, added to the fact that all the industrial applications of cellulose specially involve its colloidal characteristics, we have limited our present treatment of the subject to this particular aspect. We now give a brief systematic résumé of the BrOperaee of cellulose as a chemical individual, these tyyical charac- teristics being those of cotton cellulose. CELLULOSE.—Generally the non-nitrogenous skeleton of vegetable tissues. Type: the fibre-substance of cotton, purified from associated ‘‘impurities’’ by processes of (1) alkaline hydrolysis and oxidation (bleaching) ; (2) of digestion with hydrofluoric acid, etc., to remove mineral impurity. (C 44:4) Composition.—Hlementary ; H 6°2; whence the empiri- ( O 49°4 eal formula Cg.H 400s. Constitution undetermined. Is variously regarded as :— Aldose, (1) Polyhexose (anhyd ride) Sw Oak . : e E : , . Quercus pedunculatus . 2.86 yt oe - $5 : : * . 4 Saito Alder . : 3 ; ; . Alnus glutinosa ‘ Paro Ash . . Stem : ; ; . Fraxinus excelsior, L. eRe Fi : . Shavings from stem. F 3 :, . 269 5 5; . Stem shavings extracted . 7 260 7 : . Shavings from branches . 5 7 oO Ue . (Shavings from branches ) 2-91 ae iy . | extracted . : 3) 2 i Jivee 02 . Stem : : : . Abtesexcelsa . d . 215 ” ° : ” . 2 “ é ” x : 2°25 7 As . 5 : % : 2°39 _ ,, (central zone) . ‘ iy ip ‘ ; . .2'59 MS 5, (sap wood) A ; $ or : : . 2:32 he eC ; ; : } . Abies pectinata, DC. . 2:45 Pine . : : F ; : . Pinus sylvestris, L. . . 2°25 ms Stem ; i . . Pinus laricis . ; ve? OS ide, : 5 : : , : Hf ; ; : ae Cherry - : ; : . Prunus Avium, L. . hee” ests) Larch : tf ; : : . Larix europea, DC. . . 199° Sete ibis: ; 4 ; ; : F 7 fe : 2°68 Lime . : ~ : ; . Tilia parvifolia ; Pair) 3) Mahogany . . : ‘ 4 . Swietenia Mahagom, L. . 2:66 Walnut. hs i j : . duglans regia, L. : Nee ey pea es . Shavings from stem : 3 7 : Eso Poplar . Stem : : ; . Populus alba. ; Sees) Beech : i : : : . Fagus sylvatica Eom ff Vez ; 4 ; : ; ; a a ‘ eer Oe MLA 5 » shavings . : ‘ re i; : acta 1“ Hxtracted” signifies previously exhausted with water, alcohol, and ether. Otherwise the specimens were analysed without previous preparation. CELLULOSE AS A CHEMICAL INDIVIDUAL 65 CHs p.ct. Klm . . Stem . i : . Ulmus campestris pe ate: :. : : ,, Shavings extracted . . mp i Ae Dia gs) Willow : : P : , . Salia alba ‘ : ae ol B. Frsrous Propucts.—Natural and prepared. Jute (Lignocellulose) . : : : : : ; f : me Sei Swedish filter paper : : : A ; ‘ : . m0 Cotton p ‘ : : : ‘ ; ; ‘ ; ; = 0:0 Flax, unbleached . : ; : . Linwn usitatissimum 7 00 Hemp e F : : : . Cannabis sativa ; 3 0°29 China Grass, unbleached , ; . Béohmeria nivea ; ep Oy Sulphite (Cellulose) : : . Pinus sylvestris ‘ . 0:34 C. MISCELLANEOUS. Cork : , ; ; : : . Quercus suber . : . 2°40 ; : : : : : : 3 y : Ay Nutshells : : : . duglans regia . : . 374 Lignite (Wolfsberg) : : ; ‘ : : . 244 Brown coal 0:27 In reference to actual molecular proportions it is to be noted that in the sulphonated derivatives obtained from the lignones of coniferous woods the proportion is indicated by the formula CyHo(CHs)250O1. The localisations of these methyl groups is a present object of investigations ; and their presence is established in the celluloses isolated from the ligno-celluloses. Thisis taken as an indication of a genetic relationship between cellulose and lignone. We may now set out the main features of the chemistry of the igno-celluloses in a brief *éswmé as follows :— With the typical characteristics of the celluloses as complex aggregates, the ligno-celluloses similarly react with the zine chloride reagents to form colloidal solutions ; also to form esters with nitric acid, acetic anhydride and benzoyl chloride, respectively nitrates, acetates, and Wake, F 66 WOOD PULP AND ITS USES benzoates. But such reactions are in the main those of the cellulose constituents of the complex, the latter remain- — ing unresolved. The lignone groups with which the cellulose is combined or associated are sharply differen- tiated from the cellulose not only by higher carbon per- centage and low molecular proportion of OH groups, but by constitution; they are unsaturated, cyclic compounds, and hence react synthetically with chlorine, bisulphites and nitric oxides. They are greedy of oxygen, and are profoundly attacked by all oxidising agents, are even subject to progressive attack by atmospheric oxygen. Hence the ligno-celluloses as con- stituents of papers lower the qualities of these important industrial products, not only from their inferior intrinsic paper-making quality, but from the changes which take place as a result of atmospheric oxidation: these are, discoloration and loss of tenacity. Cellulose, as a satu- rated compound, is free from this cardinal defect, and we have practical evidence of this in the extraordinary resistance to atmospheric influences of papers and textiles which have been preserved to us from the Middle and earlier ages. Associated with these constitutional features we have a well marked and diversified dyeing capacity : the ligno- celluloses are dyed easily and by colouring matters of widely varying constitution, whereas the celluloses proper have a selective or limited tinctorial capacity. As regards intrinsic “‘ colour,” the ligno-celluloses occur in forms which would be described as grey, yellow or brown —but such colours are mostly due to associated by-products. When freed from these by certain standard methods of — CELLULOSE AS A CHEMICAL INDIVIDUAL 67 “bleaching” they assume a bright cream to whitish colour. But bleaching processes are based upon alkaline and oxidising treatments, to both of which the lignone con- stituents are extremely sensitive. Hence the limitations of ligno-cellulose textiles, such as jute, in respect of colour. The substance will not sufficiently resist the necessary treat- ments for a “high bleach.”’ Another feature of inferiority is a joint product of the relative shortness of the ultimate fibre and want of resistance to the chemical actions of hydrolysis and oxidation. From a practical point of view the ligno-celluloses are composed of cellulose units of short dimensions (1—3 mm.) cemented together by the lignone components. When these are removed the fibre is disin- tegrated ; for itis evident that structural units of }in. length cannot cohere, and the strength of a yarn or fabric pre- senting this condition can only be that due to the adhesion of the fibres, as in a sheet of paper. When wetted the adhesion is reduced to a fractional proportion. Hence the bleaching of ligno-celluloses is a matter of practical com- promise, and a ligno-cellulose fabric, bleached or unbleached, is always tending, however slowly, to disintegration, as a result of the attack of the natural and all-pervading agencies oxygen and water. It is necessary for a thorough grasp of the chemical technology of the woods, to take the logical road of studying the jute fibre as a structural type, and the jute fibre-substance as a typical ligno-cellulose. From the latter point of view it occupies the mean position between the celluloses and the perennial woods, and it will be found to be generally true of the characteristic reactions of these substances. Thus jute is attacked by the F 2 68 WOOD PULP AND ITS USES cuprammonium reagent and for the most part dissolved ; but the ligno-celluloses of the woods are scarcely affected. Strong solutions of the caustic alkalis produce the effects of ‘‘ mercerisation ”’ upon jute and fibrous ligno-celluloses of similar composition, but not upon the woods. Moreover, if mercerised jute, retaining the soda (NaOH) be exposed to carbon bisulphide, synthesis of a xanthogenic acid occurs, as with the celluloses. But the reaction is compli- cated by the presence of the lignone groups, and the product, instead of -being entirely soluble to a structureless solution, is swollen or distended by water to practically indefinite limits, and after being so distended, if then decomposed it reverts to a fibrous mass. In the case of the woods, on the other hand, there is no perceptible attack even on prolonged joint action of the alkali and carbon bisulphide. The higher proportion of lignone con- stituents in the woods, with decreased percentage of cellulose, has the effect, therefore, of producing a condition of resistance to reaction, or chemical inertness. Doubtless this is related to the physiological functions of the woods and their persistence during the prolonged period of life of trees; and this property of inertness is attained by increase in groups which are highly reactive and extra- ordinarily “ labile.’ The result appears to be paradoxical, and involves a natural equilibrium of obviously profound significance. This will be more fully appreciated from a consideration of certain characteristic colour reactions of the ligno- celluloses, which are a certain measure of, being quantita- tively related to, their lignone constituents. Ferric Ferricyande.— The red solution which results CELLULOSE AS A CHEMICAL INDIVIDUAL 69 from the interaction of ferric salts and alkaline ferri- cyanides in solution thus :— FeCls + K3FeCys = 3 KCl + FeCy, colours the lgno-celluloses a deep blue as a result of deoxidation of the ferric compound and reduction to the complex cyanides known as Prussian blue, Turnbull’s blue, etc. These separating as colloidal hydrates are deposited in a state of intimate union with the ligno- cellulose substance, and in the case of the jute fibre it is easy to see by microscopic examination that the colloidal blue pigment is structurally incorporated with the fibre substance. The amount so combining may be 380—40 per cent. of its weight, without changing the external character- istics of the fibre, z.e., form and lustre. The reaction is of use in following the progressive elimination of the lignone constituents in the processes of isolating cellulose. Students who wish to follow up this interesting reaction are referred to Journ. Soc. Chem. Ind. Phenols. — The aldehydic and ketonic constitution of the ligno-celluloses determines characteristic reactions with aromatic hydroxy derivatives or phenols. One of these is exceptionally striking. Phloroglucol, the symmetrical trihydroxybenzene (C¢Hs . O'H . O°H . 0’H) in solution in aqueous hydrochloric acid of 1:06 sp. gr. reacts with production of coloured derivatives of magenta-red hue. The depth of colour developed is constant for any given ligno-cellulose, and may be used asa quantitative estimation of ligno-celluloses in intimate admixture with non-reactive substances such as cellulose. 70 WOOD PULP AND ITS USES Ordinary printing papers are a mixture of ‘ ground wood’’ pulp, and ‘“‘ chemical” pulp or cellulose, and the depth of coloration obtained in moistening with the ‘“‘ phloroglucol reagent” affords an approximate measure of the proportion of the former or ligno-cellulose. A closer study of the reaction has shown that it consists of two phases; the coloured bodies result from a minor reaction reaching a maximum with less than 1 per cent. of the phenol per 100 parts of the ligno-cellulose: the major reaction takes place without development of colour and ‘‘ fixes’’ a further 6—7 per cent. of the phenol in com- bination as a productof condensation. The colour-reactions appear to be due to aldehydes of the furfural type, probably hydroxy furfurals. As a result of this further investigation a more strictly quantitative method has been devised which measures the total phenol combining, and by calculation the proportion of ligno-cellulose in mixtures. (See Ber. Deuts. Chem. Ges., 40, 3119, 1907.) Aromatic Bases, such as aniline and substituted anilines react with constituent groups of the ligno-cellulose complex, giving characteristic yellow to orange colorations. With dimethylparaphenylenediamine the reaction 1s more striking, the colour developed being a ‘“ magenta”’ red. With the ligno-celluloses in their normal state the colorations are constant, and are therefore an approximate quantitative measure of the proportion of ligno-cellulose in admixture with non-reacting substances such as cellulose. The method devised by Wurster consists in developing the colour reaction and comparing the depth of colour with a eraduated scale of fixed tints. CELLULOSE AS A CHEMICAL INDIVIDUAL 71 It is to be noted again that these reactions are not characteristic of the ligno-cellulose as such. They are weakened by treatment of the ligno-celluloses with reagents of feeble intensity, such as sulphurous acid and sulphites under conditions which leave the lgno-cellulose itself unaffected. They are reactions, as in the case of the phenols, with by-product groups, invariably present. There is evidence that these groups are the same as those which react with the phenols. (See also Ber. Deuts. Chem. Ges., 40, 3119.) Tigno-cellulose and Photo-chemical Phenomena. We cannot close this theoretical account of the lgno- celluloses without introducing the researches of the late W. J. Russell on “ The Action of Wood on Photographic Plates in the Dark” (Phil. Trans. B., 197, 281, 1904; also Lec)... 10, 000 > 90; 376). We are indebted to Mr. W. F. Bloch, who assisted Dr. Russell in these investigations, for the following notes of their results :-— Russell found that all the woods were able to give definite pictures upon a photographic plate, in absence of light. The action takes place when the wood is kept at a considerable distance from the plate; but for perfect definition, contact was necessary. The pictures usually corresponded with the visible structure of the wood ; but in some cases there was a marked differentiation. This selective activity appeared to depend in part upon the resinous constituents of the wood and its disposition on the cells; but also in part upon the nature of the cell-wall 72 WOOD PULP AND ITS USES structure itself, which in cases offered much resistance to the passage of the active bodies. On the evidence the active bodies must be regarded as an emanation, but differing entirely from radio-active emanations. . All the properties ascertained identify the substance with hydrogen peroxide. Ordinary photographic dry-plates may be used to produce this effect ; care must be taken to select such as have been preserved in wrapping materials themselves unable to act upon the plates. | The action takes place slowly at ordinary temperatures (one day to twenty-one days) according to the nature of the specimen, but rapidly at 50—55° C. (half to’ eighteen hours). The shorter exposures give sharper pictures, which observation accords with the conclusion that the active body is of the nature of a vapour or volatile compound. Bark and pith structure are almost inactive. Within the bark there is a bark-forming tissue, which gives alternate layers of active and inactive tissue. The latter was also found to have the property of being impervious to hydrogen peroxide. The activity of the woods is increased in all cases by exposure to strong light, and observations on the spectrum showed that the blue end was particularly active. The increased activity disappears on keeping the speci- mens after exposure in the dark. Resinous substances extracted from a number of woods were found to be all more or less active. Para-abietic acid was prepared and found to be particularly active. It is Action , of wood on photographic plate in the dark (W. J. Russell, Phil. Trans. B. 197—281),. : Fig. 138.—Oak. Fig. 134.—Larch. "ITT YOIOON—'aeT “O17 ‘gonidg—‘oe] “OI VY CELLULOSE AS A CHEMICAL INDIVIDUAL 76 well known that this body shows the phenomenon of aut- oxidation, which is no doubt associated with its unsaturated constitution. The fossil resins show slight activity; coal also shows activity, and attempts were made to apply this to the identification of different types of coal. Woods were exhaustively treated with resin solvents, but were found to be still active, and the evidence goes to show that we are dealing with a definite property of the ligno- celluloses. It is to be noted that a short exposure to steam or to chlorine gas renders the wood substance inactive. The action is arrested in an atmosphere of carbonic gas, but is stimulated by the presence of oxygen. Experiments in which the active substance in sufficient mass was swept witha stream of air, and the current of air afterwards made to act upon a photographic plate at some distance, showed that the active substance could be carried forward. | It was also found that diaphragms carrying any substance capable of absorbing and destroying hydrogen peroxide arrested the action. The investigation is stillat this empirical stage. Russell has left an interesting legacy of highly suggestive observa- tions, and the matter invites further investigation, as the exploration of the causes is calculated to throw a very important light on the natural chemical equilibrium of the higno-celluloses. CHAPTER III WOOD PULPS IN RELATION TO SOURCES OF SUPPLY: FOREST TREES AND FORESTRY THE use of wood pulp as a raw material for the manu- facture of paper is of comparatively recent origin, its commercial application for this purpose dating from 1869, when about 60 tons of mechanical-ground wood pulp were exported from Norway to Engiand. In the following year the quantity rose to 500 tons, and from that year onward the industry has grown by leaps and bounds, the total amount of wood pulp imported in 1909 being over 500,000 tons. At the present rate of consumption of wood. for paper- making, the devastation of forest areas has become so serious a matter that the Governments of the various countries in which these forests exist are taking vigorous steps in the first instance to prevent their absolute destruc- tion, but further to secure a systematic upkeep. It is very difficult to arrive at accurate figures repre- senting the world’s production of wood pulp; but from the sem1-official published returns an approximate estimate may be obtained. In dealing with these returns it is to be noted that the systems of measurement, the methods of recording results, and the tabulation of the records are different in ~I =I SOURCES OF SUPPLY each country, and such figures are of little service unless reduced to some common standard of measurement. TABEES SHOWING ANNUAL PRODUCTION OF Woop PULP FOR VARIOUS COUNTRIES, CALCULATED ON THE AIR Dry Basis (1907—1908). Country. Be dep tae oh. eatedey tan ae ee oot Germany . : 315,000 320,000 635,000 Norway . : 421,000 270,000 691,000 Sweden . 78,000 510,000 388,000 Finland . : 69,000 32,000 121,000 America . : 868,000 988,000 1,856,000 Canada. ; 565,000 172,000 737,000 2,316,000 2,312,000 4,628,000 The most convenient unit which may be taken as the basis of measurement for comparison is the “ cord”’ of wood, consisting of a number of short logs, each 4 feet long, piled up in a space 8 feet long and 4 feet high. Such a pile of logs measuring 8 feet x 4 feet x 4 feet = 128 cubic feet, is called a “cord” of wood. The unit of weight may be taken in terms of the English ton of 2,240 lbs. (See p- 85.) These figures do not convey even in such concrete 1 The sources of information from which Table I. has been com- piled are as follows:—Germany: Figures given by Dr. Kirchner in ‘* Wochenblatt,” 1907. Scandinavia: Report British Wood Pulp Association, 1909. America: ‘‘ Wood Used for Pulp,” U.S.A. Bulletin. Canada: ‘‘ Wood Pulp in Canada,” official report, Geo. Johnston. Finland: Paper T'rade Review, 1908. rs a 78 WOOD PULP AND ITS USES form any accurate picture of the extensive cutting opera- tions which are going on, for the manufacture of wood pulp. Some idea may possibly be obtained by attempting to estimate the number of standing trees felled to supply the quantity of pulp wood mentioned. ‘This will vary in different countries according to the nature and size of the trees. According to general practice, the large trees are reserved for lumber and the manufacture of boards for building purposes, so that the trees used for pulp may be taken at an average diameter of about 9 inches. The ordinary spruce or pine tree of this diameter will yield three logs, each 16 feet long, and when the logs are cut into 4-feet lengths, twelve pieces. The number of pieces required to give a piled cord of 128 cubic feet capacity is about sixty, so that for each cord five trees would be necessary. Assuming that 1 ton of dry chemical pulp is obtained from 2+ cords of wood, and 1 ton of mechanical pulp from 14 cords of wood, then the total quantity of timber to be cut for the production of the amount of wood pulp shown in Table I. would be about eight million cords. A certain proportion of the trees cut are faulty and decayed, while some are lost in transit from the forest to the pulp mill, so that the actual number felled for pulp wood is somewhat in excess of the quantity indicated. In relation to forestry and the destruction of forests, we have to consider, in addition to the wood cut for pulp, the number of trees required for timber, and the sum of these figures reaches formidable dimensions. Forestry.—The available forest areas of different countries have been given by Schlich as follows :— SOURCES OF SUPPLY 79 TA Bie Lik Country. Acres (millions). Canada . ; : : ’ : 4 800 America . : : : 400 Russia . y : : q . : 500 Austria-Hungary . ; 46 Germany . : ; ; 35 Sweden . , : ; 49 Spain . : , 21 Norway . : ify) France .. ; 3 : 23 Italy ; 10 Roumania ; : : , 5 Great Britain . ; : : ; a The preservation of the forests in wood-producing countries is thus an acute problem, and of recent years the subject of afforestation has aroused considerable interest in England, especially in regard to the industrial possi- bilities ; but incidentally also as affecting rainfall, and therefore general agriculture. One of the most important questions, therefore, in this connection is the calculation of area necessary to supply a mill continously with wood pulp. For example, What area of land planted with spruce and hard woods would be necessary to supply a mill having an output of 800 tons of newspaper per week ? This quantity of paper would require 200 tons of mechani- cal pulp and 100 tons of sulphite pulp per week, amounting to an annual supply on a basis of fifty weeks’ work, of 10,000 tons mechanical pulp and 5,000 tons sulphite pulp. 80 WOOD PULP AND ITS USES Taking 1} cords of wood as the quantity required for 1 ton of mechanical pulp and 2} cords of wood for 1 ton dry sulphite pulp, the annual supply of wood necessary is 12,500 cords for mechanical, and 11,250 cords for sulphite pulp, or an approximate total of 25,000 cords. The actual amount of spruce or pulp-producing woods per acre varies enormously in different countries and in different localities, and it is difficult to fix an average. In thickly wooded areas which have not been cut over, the quantity frequently reaches 40 to 50 cords per acre; but on timber lands which have been continuously “ operated” the amount may not exceed 8 to 4 cords. Taking 10 cords to the acre as a moderate and probable allowance, then in the above case 2,500 acres would be required to give the wood pulp necessary for one year. If the total forest area was 100,000 acres, then the timber available would be sufficient for forty years’ supply. During that period the spruce largely reproduces itself, so that by progressive and careful management of the forest in the matter of planting and reproduction, an area of 100,000 acres should afford a perpetual supply to the mill quoted. Mr. Parker Smith, in a paper entitled ‘“ Afforestation,” read before the English Paper Makers’ Association, 1910, says that at the Canadian Convention one manufacturer stated he could run his mill perpetually on a grant of 25,000 acres, which would permit of his cutting on a forty years’ rotation, and yield, on a basis of 10 tons of pulp per acre, a total of 6,000 tons annually. Comparing this statement with the one already quoted, and assuming that the 6,000 tons consisted of 4,000 tons mechanical pulp and 2,000 tons sulphite pulp, the weekly SOURCES OF SUPPLY 81 production of the mill works out at 120 tons of paper per week, requiring 10,000 cords of pulp wood. On this com- putation the manufacturer referred to was calculating the quantity of pulp wood per acre to be 16 cords. Pinchot, the well-known American forestry expert, has carried out some valuable and elaborate experiments on the subject of the growth of spruce. A large area of forest land was carefully examined for the nature of the timber, its condition, growth, and other important information. Careful attention was given to the rate of the growth of the timber both in the virgin forest and also on areas which had been previously ‘‘operated” for timber. The data obtained in this investigation enabled Mr. Pinchot to con- struct tables showing the amount of timber which could be cut from the forest, and the number of years which would elapse before an equal quantity of timber could be cut from the same area. One example of this will be sufficient :— A man owns 100,000 acres, yielding on an average 7 cords per acre of spruce 10 inches and over in diameter. How much can he cut annually if he wishes to obtain a sustained annual yield, and how soon can he return to the portion cut over the first year, and cut the same amount of timber about the same diameter limit as at first ? In the tables published by Mr. Pinchot the total amount of wood with a diameter limit of 10 inches appears to be 100,000 x 7 cords = 700,000 cords, while the same yield of pulp wood could be obtained after thirty-seven years. The area to be operated annually will be 100,000 ~ 37, namely, 2,700 acres. ‘The annual cut of wood will be W.P. G 82 WOOD PULP AND ITS USES 700,000 — 87 = 19,000 cords. This illustration, taken at random from the experiments of Mr. Pinchot, coincides closely with the other cases quoted, and if the diameter limit was reduced to 9 inches a larger annual cut would have been obtained. The problem of forestry has been studied and worked out on a successful commercial basis in several Huropean countries. In Saxony, for example, the State control of an area of 480,000 acres has resulted in a large and profitable turnover, giving a steady revenue of increasing amount, as well as constant employment to skilled labour. In fifty years the State has realised the sum of £40,000,000, and the careful scientific methods of cutting, aided by proper attention to means for reproduction, has improved the quantity and quality of available timber, At a recent meeting of the Canadian Forestry Convention it was shown that the amount of standing timber in the State of Saxony had increased by 16 per cent., even during the period of constant cutting, and that the net revenue was 22s. as compared with 4s. fifty years previously. The same satisfactory results are shown by other’ countries in which forestry as a commercial undertaking has been treated seriously. In England the matter has been under consideration for some time, and the Report of the Committee on Re- afforestation, issued in 1909, is full of useful and suggestive evidence. It is interesting to note that the waterworks committees of several large municipal corpora- tions, such as Liverpool, Manchester and Birmingham, have taken up the question, primarily for the purpose of conserving the rainfall incidental to the watershed under SOURCES OF SUPPLY ° 83 control, and then turning the large areas thus acquired for maintaining the water supply to useful account by planting trees. The attractiveness of afforestation in the United Kingdom is clearly shown by the Committee’s report. The con- clusions arrived at are briefly— 1. Afforestation is a practicable scheme, the available area in the United Kingdom being 9,000,000 acres. 2. The best rotation to secure a continuous yield of wood requires 150,000 acres to be dealt with annually. 3. Afforestation is a productive investment for the development of the full scheme, for 9,000,000 acres would require an annual sum of £2,000,000. The net deficit would be £90,000 in the first year, rising pro- gressively to £38,131,250 in the fortieth year, in which period the forest becomes more than self-supporting. 4. After eighty years the net revenue at present prices for timber should be £17,500,000. This represents 3% per cent. on the net cost calculated at accumulating compound interest at 3 per cent. 5. Afforestation creates a new industry which does not compete with private enterprise, and would afford permanent employment to one man per hundred acres, and temporary employment to a large number of men during the winter months. Cost of Afforestation.—The Committee gives the following example :— We assume, as regards expenses, that :— 1. 150,000 acres are annually afforested for sixty years, and that the cost of the freehold and expenses of afforesta- tion amount to £13 6s. 8d. per acre. G 2 84 WOOD PULP AND ITS USES 2. The annual outlay for administrative expenses is 4s. per acre. 8. One-third of the area is worked on a forty years’ rotation, and two-thirds on an eighty years’ rotation. 4. The cost of re-afforestation is £6 10s. per acre; and 5. The rate of interest is 8 per cent. per annum. We further assume, as regards receipts, that— 1. Thinnings take place at the end of the twentieth year, and at the end of each successive decade from the date of planting. 2. The net receipts for the initial thinnings amount to 2s. 6d. per acre, and for the succeeding thinnings are at the rate of £3, £6, £9, £12, and £15 per acre respectively. 8. The area which is afforested on an eighty years’ rotation yields £175 per acre on being clear-felled at the end of eighty years. 4. The area which is afforested on a forty years’ rotation yields £60 per acre on being clear-felled at the end of forty years ; and 5. The rate of interest is 8 per cent. per annum. The annual deficit on the transaction rises from £90,000 in the first to £3,131,250 in the fortieth year; in the forty-first and up to the sixtieth year the forest becomes practically self-supporting ; in the sixty-first year, and sub- sequently, an increased revenue is received, but it is not until the eighty-first year that the full results are obtained ; in this year and subsequently an approximate equalised revenue of £17,411,000 per annum being realised. Further’ calculations show that the value of the property would then. be £562,075,000, or £106,9983,000 over and above the cost of its creation. The equalised annual revenue of £17,411,000 SOURCES OF SUPPLY 85 represents a yield of £3 16s. 6d. (approximately) per cent. on the excess of accumulated charges over receipts. Measurement of Pulp Wood.—The systems for measuring wood used in the manufacture of pulp differ in the several countries. Scandinavia.—The wood is measured in terms of fathoms or of cubic metres, the price paid for raw material being determined by reference to a table showing the sum to be paid for logs of varying lengths and varying diameters. One fathom = a Toot, One cubic fathom = 216 cubic feet. Germany.—Wood is usually measured in Germany and other Continental countries by the cubic metre. silver Fir (India) », silver Fir | (Hurope) Hemlock Hornbeam Larch Maple Paper Birch Pines : Black Pine . White Pine . Pitch Pine Poplar . i White Poplar Black Poplar Sallow (Willow) Sandalwood Spruce . f White Spruce _ Tamarac Willow Coniferee. SOURCES OF Botanical name. SUPPLY Robinia pseudacacia Alnus glutinosa Fraxinus excelsior Pyrus aucuparia Populus tremula Abies Fraseri Tilia Americana Fagus silvatica Betula alba Castanea sativa Populus monilifera Sahx fragilis Taxidium distichum Ulmus campestris Picea excelsa Abies pindrow Abies pectinata Abies canadiensis Carpinus betulus Larix Europea Acer dasycarpum Betula papyrifera Pinus austriaca Pinus strobus Pinus palustris Populus Populus alba Populus nigra Salix capreea Santalum album Picea excelsa Picea alba Larix americana Salix nigra Cone-bearing trees Deciduous or leaf-bearing trees 89 gs) 23, German. 35 2 3 TQ: OD = aoe Schotendorn che lkoas Gemeine-erle (Roth-erle) "46 | 29°0 Weiss-esche ‘65 | 40°8 Eber-esche 54 | 34:0 Zitter-pappel (Aspenholz) 50 | 31°3 36 | 22°2 Linde 45 128-2 Rotbuche 75 | 46°8 Birken-holz °64 | 40°0 Kastanje "45 | 28:1 Wollpappel “39 | 24:2 Bruchweide oA yal 2Sc0 Cypresse "45 | 28°3 Steinlinde (Roth- rister) 69 | 43°3 Fichte. ohre ‘49 | 30°0 Tannenholz-Tanne | *46 | 29°0 Tannelholz-Tanne | °49 | 30:0 Schierlingstanne | °42 | 26°4 Weissbuche (Hagebuche) 72 | 45:0 Lorche "74 | 46°1 Ahorn 52 | 32°8 ‘O0 Roe Kuefer. Nadelholz Schwarztohre 57 | 35°4 Wehmuthskiefer 38 | 24:0 Gelbkiefer “70 | 43°6 Pappel ‘40 | 25°6 Silberpappel ‘48 | 30-0 Schwarzpappel 48 | 30-0 Sahlweide iyi |b ai!) Santalholz ‘98 | 60°0 Fichte (‘Tanne) 42 | 26°7 Weisstanne AOr 20% Lorche *62 | 38°9 Weide Hs Ey fa Nadelholz. Laubholz. 90 WOOD PULP AND ITS USES The History of Mechanical Wood Pulp.—The possibility of using wood for papermaking seems to have been deduced from the Réaumur observation that wasps build their nests from partially decayed wood which they obtained from trees or timber. In 1765 J. C. Schaffer, a priest in Regensburg, published a book containing samples of paper made from many raw materials, and referring especially to wood, wrote: “it must be possible, though with different methods, to make paperstuff from wood and consequently use it instead of the ordinary rags for papermaking.” This is an interesting statement in view of the fact that nothing was then known of the use of alkalies or other chemical agents for reducing fibrous materials to pulp. Schaffer experimented with the material of the wasps’ . nest, with sawdust and shavings. From some seven or eight species of wood he made excellent sheets of paper, having regard to the means at his disposal. He published a second edition of his book, entitled, ‘‘ Simtliche Papier- versuche-Nebst 81 Mustern und 13 Kupfertafeln,” in 1772, and enlisted the services of a papermaker, Meckenhauser, to enable him to produce some better results. In 1800 Matthias Koops, a Dutchman, published a book which he printed on paper made from straw pulp and dedicated to King George Jil. He added an appendix to his work which was printed on paper made entirely of wood pulp, an idea suggested to him no doubt by the work of J.C. Schaffer. Koops was a man of some enterprise, for he also issued a work on paper made entirely from old waste paper, this being probably the first attempt to utilise old waste material for such a purpose. In 1840 Friedrich G. Keller, a young weaver of Haynich, SOURCES OF SUPPLY 91 in Saxony, reading in a scientific journal of the great scarcity of rags as material for papermaking, resolved to keep his.eyes open for a substitute. In 1848 his attention was called to the remarkable paperlike appearance of the wasps’ nest, and recollecting that in his school days he had ground down cherry stones on an ordinary grindstone in order to make a cherry chain, he tried the effect of holding a piece of wood against the revolving stone. To his great delight the experiment was successful, and he collected the fibres so isolated from the wood and made a minute piece of paper. Keller continued his experiments, and in 1844 manu- factured about 2 to 3 cwt. of pulp, which was beaten up with rag pulp and made into paper. In 1845 he parted with the secret of his process, and disposed of it to Heinrich Volter for the sum of 700 thaler (£140) ! The progress of the new method was somewhat slow, but improvements, including the necessary treatment for refining the pulp, or removing the coarse chips, were introduced, and towards 1860 the process was put on a more satisfactory footing. In 1862 Volter was awarded the medal of the International Arts and Industries Exhibition in London. Between 1862 and 1865 seven or eight pulp mills were erected in Germany and Scandinavia and the manufacture of ground wood pulp on a large scale became an accomplished fact. History of Chemical Wood Pulp.—The early attempts of Koops in 1800 to utilise straw, and his few experiments with wood as substitutes for rag, may be regarded as the starting point in the history of chemical wood pulp. The materials were probably boiled with some crude soda ley 92 WOOD PULP AND ITS USES and subsequently beaten into pulp. About this period soda ash, caustic soda, chlorine and bleaching powder and other chemicals had been introduced to the manufacturing world, so that the possibilities for reducing vegetable products to the condition of pulp were much greater. In 1857 Houghton patented a process for digesting wood with caustic soda at high temperatures in closed vessels. In 1868, Tilghmann, an American chemist, suggested the use of a solution of sulphurous acid gas. His early experiments were carried out in lead-lined vessels, but the work was abandoned owing to difficulties connected with the construction of suitable digestors. As Tilghmann was the inventor of a process which has become the basis of a large and important industry, the following précis of his first patent, as given by Mr. A. D. Little, may be quoted as having a peculiar interest :— The process of treating vegetable substances which contain fibres with a solution of sulphurous acid in water, either with or without the addition of sulphites or other salts of equivalent chemical properties as above explained, heated in a closed vessel, under pressure, to a temperature sufficient to cause it to dissolve the intercellular incrusting or cementing constituents of said vegetable substances, so as to leave the undissolved produce in a fibrous state, suitable for the manufacture of paper, paper pulp, cellulose, or fibres, or for other purposes, according to the nature of the material employed. I also claim as new articles of manufacture the two products obtained by treating vegetable substances which contain fibres with a solution of sulphurous acid in water, either with or without the addition of sulphites or other salts of equivalent chemical properties, as above explained, heated in a closed vessel, under pressure, to a temperature sufficient to cause it to dissolve the intercellular or incrusting constituents of said vegetable substances, one of said products being soluble in water, and containing the elements of the starchy, gummy, and saline constituents of the plants, and the other product being an insoluble fibrous material, applicable to the SOURCES OF SUPPLY 93 manufacture of paper, cellulose or fibres, or to other purposes, according to the nature of the material employed. IT also claim the use and application, in the manufacture of paper, paper pulp, cellulose and fibres, of the fibrous material produced by treating vegetable substances which contain fibres with a solution of sulphurous acid in water, either with or without the addition of sulphites or other salts, of equivalent chemical properties as above explained, heated in a closed vessel, under pressure, to a temperature sufficient to cause it to dissolve the incrusting or intercellular con- stituents of said vegetable substances. LT also claim the use and application of sulphites or other salts of equivalent chemical properties as above explained, in combination with a solution of sulphurous acid in water, as an agent in treating vegetable substances which contain fibres, when heated therewith in a close vessel, under pressure, to a temperature sufficient to cause the said acid solution to dissolve the intercellular or incrusting constituents of said vegetable substances. I also claim the recovery and re-use of sulphurous acid and sulphite from the acid liquids which have been digested on the vegetable fibrous substances, by boiling said liquids or neutralising them with hydrate of lime. In 1872 Ekman had developed a process which was commercially successful, and this was introduced into England, at Ilford, Essex, about 1884, a mill being erected a few years later at Northfleet in Kent for the treatment of wood by means of bi-sulphite of magnesia. In 1876, Mitscherlich, a celebrated German chemist, experimented with sulphurous acid and devised a method for converting wood into pulp by cooking under low pressure for a long period, producing a half-stuff eminently suitable for certain classes of paper. Numerous and extensive modifications of the original Tilghmann sulphite process have resulted in the evolution of an industry typical of modern chemical engineering. Such modifications refer to details of working, more particularly 94 WOOD PULP AND ITS USES to the type of boiler or digestor, to economy in the amount of sulphur used, to improving or varying the quality of the pulp, and to general efficiency, and are of subordinate historical interest. There has been a good deal of controversy as to the priority of original invention of this most important indus- trial development. It has always appeared to us that while Tilghmann is the pioneer from the technological stand- point, on the clear and specific claims of his patent above set forth, the practical and industrial pioneers were George Fry and his collaborator Ekman. Some years in advance of the bi-sulphite process (1869) Fry investigated the action of water only at high temperatures and pressures, paying particular attention to the volatile by-products of the complex reactions; and in this investigation secured the collaboration of the late Greville Williams, who identified furfural amongst the products of decomposition of the ligno- cellulose. Finding that the resolution of the wood under these conditions was limited by the influences of oxidation and condensation, it was then suggested by Fry to Ekman, who had become associated with these researches, to seek for a new chemical condition to antagonise these influences. In this path of logical though empirical evolution this group of pioneers may be held to have independently discovered the bi-sulphite process ; and Ekman, with George Fry, had the satisfaction of working the process to an industrial and commercial success at Bergvik, Sweden, then at Ilford, and lastly at Northfleet. The following is a chronological list of inventions for the preparation of pulp from wood by chemical reactions :— Year. 1840 1852 1853 18509 1857 1861 1864 1866 1867 1870 1870 1871 1872 1872 1880 1881 1882 1882 1883 1883 1885 1890 1894 SOURCES OF SUPPLY Name. Payen Coupier & Mellier Watt & Burgess Jullion Houghton Barre & Blondel Bachet & Machard Tilghmann Fry Ekman Dresel R. Mitscherlich Ungerer Rotter-Kellner Cross Francke Pictet & Brelay Graham Blitz Dahl Kellner Lifschutz Cross Process. Nitric Acid Soda Alkalis Alkaline salts Alkalis Dilute acids Acids Sulphurous Acid and salts Water at high temperatures Magnesium Sulphite Soda Sulphurous Acid and salts Soda Sulphurous Acid and salts Water and neutral sulphites Sulphurous Acid and salts Sulphurous Acid Sulphurous Acid and salts Alkalis and sulphites Sulphates and sulphides Electrolytic process Nitric and sulphuric acids Nitric Acid—dilute CHAPTER IV THE MANUFACTURE OF MECHANICAL WOOD PULP THe term “mechanical” or “ ground’’ wood pulp is applied to pulp which has been prepared by a mechanical process. The principle of the operation is merely the dis- integration of wood into fibres by means of a grindstone, the wood being brought into contact with the stone as it revolves. The conditions of manufacture are capable of considerable modification so that various grades and qualities of product are possible. Preparation of Wood.—The logs of wood, which have been brought to the mill from the timber limits or other sources, and which vary in length from 10 to 16 feet, are first reduced to a uniform length of 24 inches by means of large circular saws. The arrangements in a modern pulp mill for handling the logs and preparing them for conversion into pulp call for considerable skill and attention in order to produce the optimum result at minimum cost. The short pieces of wood are automatically conveyed to the ‘‘ barking”’ room and there deprived of the outer bark. The machine used for this purpose consists of a heavy circular iron disc enclosed in a strong casing. The disc is provided with three knives projecting from the surface of the disc in such a manner that when the short pieces of wood are pressed against the surface of the disc, MECHANICAL WOOD PULP ai as it revolves, they are completely denuded of the bark itself. A considerable proportion of wood is lost in this process, the amount varying from 15 to 25 per cent., according to the size and condition of the logs. The bark is generally burnt in special ovens and utilised as fuel. The clean pieces of wood may be employed for the manu- facture of either mechanical or chemical wood pulp and in practice the pieces are often sorted out, the clean wood free from dirt and knots being reserved for chemical pulp, and the inferior wood being converted into mechanical wood pulp. Cold-ground Pulp.—When the wood is ground into fibres in the presence of a large excess of water, a fine even pulp of uniform quality is produced. This pulp is known as ‘“‘cold-ground’”’ in contradistinction to ‘ hot-ground”’ pulp, which is produced under the condition of high tem- perature (infra). The machine used for the manufacture of the cold ground pulp consists of a horizontal grindstone, usually 60 inches in diameter and with 27 inches breadth of face, mounted on a heavy vertical shaft and encased in a strong cast-iron circular box, as shown in Fig.14. Around the circumference of the box there are a number of recesses or “‘ pockets” in which the short 2 feet pieces of wood are placed. The wood is pressed against the surface of the rotating grindstone by pistons operating under hydraulic pressure, water being continuously applied to the surface of the stone so that the disintegrated fibres are carried away from the stone into storage reservoirs for subsequent treatment. | Hot-ground Pulp.—When the quantity of water flowing W.P. H 98 WOOD PULP AND ITS USES to the grindstone is reduced to a minimum then the tempera- ture of the mass in contact with the stone rises rapidly on account of the friction, and the wood is thus ground to pulp WY. YG bp YU i ic : |, 2 Add ear — = eee IE? “4\ ct ke eee i \ Ls UML B Fic. 14.—View of Horizontal Grinder (A), with Section (B). under entirely different conditions. The fibres are readily torn away from the wood, and produce a pulp which is much coarser than the cold-ground pulp, the fibres being longer. MECHANICAL WOOD PULP 99 The machine used for the manufacture of this pulp consists of a grindstone mounted in a vertical position on a horizontal shaft, operated by a water turbine. The stone is enclosed in a circular iron casing provided with “ pockets” into which the blocks of wood are placed. ‘The pieces of wood are forced against the surface of the stone by hydraulic pressure. The water is supplied to the grindstone in_ limited quantity, just sufficient being used to prevent the pulp from being burnt or spoilt. The temperature frequently rises to 150° ahr., owing partly to the greater pressure of the wood against the stone, and also by the conditions under which a limited supply of water is used. Pulp of this kind works freely on a fast-running news machine— that is, as the pulp and water flow on to the wire of the paper machine the water drains quickly and freely through the meshes of the wire, and thus makes it possible for the machine to be operated at a high speed. Many of the paper machines used for the manufacture of ‘‘ news”’ with pulp of this character can be run at a speed of 500 to 600 feet per minute. The quantity and quality of the pulp produced as con- trolled by the conditions of grinding depend on (1) The sharpness of the stones ; (2) The pressure applied to the blocks of wood ; (3) The temperature of the mass ; (4) The method of applying the wood to the stone. In general terms, the quantity of the pulp is increased by the use of sharp stones and the application of pressure, the yield being highest with wood treated by the hot-ground process. H 2 100 WOOD PULP AND ITS USES The coarseness of mechanical wood pulp is merely a relative term, for it is possible to have a badly-ground wood pulp well screened, giving a coarse material of an even uniform grade, or, on the other hand, a well-ground wood badly screened giving a high-class pulp, spoilt by the presence of long chips or slivers which have not been removed. Such slivers in pulp are a fruitful source of “breaks ”’ on the paper machine, since they locally reduce the tensile strength of the web. Coarse pulp of a uniform grade does not produce “ breaks,’ but the fibres do not he closely in the surface of the paper, with the result that a large quantity of ‘‘ fluff’? is produced on the type of the rotary printing presses. | The output of a grinder is increased by sharpening the stone and by increasing the pressure applied to the blocks of wood. The effect of using sharp stones is clearly indicated by the following experimental results, obtained from two or three pulp mills :— Pounds of wood treated per hour. Ratios. Mill. Dull stones. Sharp stones. Dull stones. Sharp stones. 440 680 100 155 B 637 1064 100 167 C 628 830 100 138 The amount of wood pulp obtained from a grinder depends chiefly upon the pressure applied to the wood in contact with the stone, as shown by Kirchner’s elaborate experi- ments tabulated in the following table :— MECHANICAL WOOD PULP 101 ere Consumption of Fite pecan ans power. per hour 1 isto 1:25 2 1°95 3°30 3 2°60 a°16 4 3°16 6°60 9) 3°80 Eo2 ae) 4°05 8°05 6 4°40) 8°30 fi a°0 7:92 Yield of air-dry pulp H.P. required for 24 hours for 1 ton air-dry pulp. 86°0 06°5 47:0 44°5 44°7 44°4 49°4 59°0 The effective work of the stone under the conditions of the experiment is evidently reached when the pressure is 5°5 lbs. per square inch, for at this point the power required for a given output is lowest. Kirchner gives the following interesting table showing the influence of the condition of the stones on various kinds of wood :— PRODUCTION OF PULP PER H.P. PER 24 HOURS UNDER DEFINITE EXPERIMENTAL CONDITIONS. Woad: Well sharpened stones Pine Fir Aspen . Poplar Lime . Birch . Willow Alder . Oak Lbs. of pulp. TRUDR SS bo ATOR Om || Moderately sharpened stones. Lbs. of pulp. In a more complete series of trials Kirchner studied the relation between the power consumed with stones of varying 102 WOOD PULP AND ITS USES degrees of sharpness in producing a stated quantity of pulp and the pressure on the surface of the stone. These trials were conducted with the hot-grinding process, and the amount of pulp produced per twenty-four hours was taken as 100 kilos (say 220 lbs., or nearly 2 cwt.), the stones being worked under conditions giving this output. ‘Three stones —fine, medium and coarse grades—were selected for the experiment. The general results obtained show that as the pressure increased, the power required decreased up to a certain point, when any further pressure at once created a demand for greater power. This is admirably shown in the diagram Fig. 15, where the experiments with the three classes of stone are shown by the curves, A, fine; B, medium; C, coarse. The maximum output was obtained under the following conditions :— 1 Pressure. F a Output in Stone. Lbs. per sq. in. Horse-power. 24 hours. A. Fine ; ‘ 4:2 4 220 lbs. B. Medium . F 12°6 2°4 220 lbs. C. Coarse. : 8°4 2 220 lbs. Excess of pressure is shown by the sudden upward turn of the curves, though with the coarse stone this point has not been reached. The immersion of the lower half of the stone in water had a remarkable effect on the results. The pressure can be increased enormously with a corre- sponding greater efficiency in the work of the stone, although MECHANICAL WOOD PULP 108 Pressure in Ibs. per square inch of Surface ane VE aS bee mre aeee) uae ALE e) ~ “SUN0Y HZ J8d dng > WMI Z anb 07 pauinbas aH Fie. 15.—Curve for illustrating Power Trials. 104 WOOD PULP AND’ Tis 30SiEs the power required does not vary much. This is shown by the curve D, which after a pressure of about 8 lbs. to the square inch assumes a horizontal position. » Kirchner found that the output per unit of area of the total grinding surface was almost proportional to the pressure. | The diagram in Fig. 15 represents the results of some of the more important tests. Curve A.—With a pressure of 14 lbs. per square inch a stone with fine surface required, in twenty-four hours, 74 h.p., and with a pressure of 3 lbs. per square inch, 43h.p. The greatest production was obtained when the pressure reached 44 lbs. per square inch, when the power required to treat 2 ewt. of wood amounted to 4 h.p. Curve B.—This curve represents the work of an average stone which required 3 h.p. under a pressure of 44 lbs. per square inch. The power under a higher pressure of 14 lbs. per square inch was only 24 h.p. for the same production. Curve C represents the work of a coarse stone, the amount of power for a given production being reduced by the increase of pressure down to a certain point, after which any further increase of pressure required a greater amount of power. This is shown by the sudden rise of the curve when the pressure reached 13 lbs. per square inch. Kirchner in his interesting experiments pointed out that these tests show the relation between the production of pulp with different kinds of stone at different pressures, and shows that for a maximum output under economical condi- tions it is important to choose the right pressure for a given stone. In a further series of experiments he kept MECHANICAL WOOD PULP 105 the stone partially immersed in a mixture of pulp and water. The results are shown in curves D and KE. Curve D.—With a pressure of 44 lbs. per square inch the power required for the production of 2 ewt. of pulp per twenty-four hours was 54 h.p. The gradual increase of pressure was accompanied by a reduction in the amount of Fic. 16.—Shaking Screen. power required, and with a pressure of 15 lbs. per square inch the power was reduced to 4 h.p. The practical effect of the greatly increased pressure was seen in the finer condition of the pulp. Screening.—The pulp from the grinders is carefully screened to remove all chips and insufficiently ground pulp. Many forms of apparatus are employed, but all are based upon the same principle, the use of plates perforated with 106 WOOD PULP AND ITS USES fine slits or circular holes allowing all the finer pulp to pass through, but retaining all coarse pieces. The shaking screen shown in Fig. 16 consists of a horizontal shallow tray perforated with fine slits. The pulp, mixed with large quantities of water, flows on to the tray, which is Fic. 174.—Centrifugal Screen for Wood Pulp. kept in a violent state of agitation, and the fine pulp together with the water falls through the slits, while the coarse stuff is gradually forced along the surface of the tray and eventually falls over the edge into a trough of water or a travelling band conveyor. A flat screen is worked on a somewhat similar principle, but the motion of the plate is due to a violent agitation MECHANICAL WOOD PULP 107 produced in a vertical direction instead of being to and fro in the horizontal direction. This produces a partial suction. The centrifugal screen, Fig. 17a, the latest form of apparatus for separating out the coarse pulp, is a round vessel, containing a circular screen built up of perforated ATM Te Uf. WE uN) A\\\ VAN ee - s- > > = SS a pete A EERE OS ert 5 Fic. 178.—Section of Centrifugal Screen for Wood Pulp. plates, which rotates at a high rate of speed, the fine pulp being forced through the slits by centrifugal force. The capacity of a screen is usually expressed in terms of the weight of dry pulp obtained in a given period. Such figures are not of much value without details as to the size and number of the perforations per square foot of area, as the capacity is readily increased by the simple process of enlarging the slits or holes. 108 WOOD PULP AND ITS USES Removal of Water.—When the pulp has been properly | screened, it is treated in a wet press machine in order to remove the large quantity of water with which it is mixed, and to produce a pulp fit for shipment to the paper mill. The dilute mixture is pumped continuously into a large vat in which rotates a hollow drum the surface of which is made of fine wire gauze. The pulp adheres to the drum, while the water is forced through the wire cloth and flows away into a trough fixed outside the vat. The thin skin of pulp is carried up above the surface of the water in the vat and is picked off by a travelling felt passing over a roller which is in contact with the drum. The thin sheet passes between small rollers, which squeeze out more water, and is then wound up in a continuous roll on a large wooden drum until it forms a thick sheet. This is removed at intervals either by hand or automatically. In the most approved form of wet press machine the thick sheet is cut off at regular intervals by a knife which falls automatically. The sheet of pulp is therefore always of uniform thickness and weight, provided reasonable care has been exercised in keeping the ratio of water and pulp fairly constant. From the wet press machine the pulp is obtained in the form of thick sheets containing about 75 per cent. of water. The sheets of pulp are finally submitted to pressure in powerful hydraulic presses which remove a further quantity of water and give a product containing 50 per cent. of air- dry pulp and 50 per cent. of water. ‘These sheets are packed in bales of 4 cwt. and 2 cwt. capacity, and then fastened up with stout iron wire and wooden battens. MECHANICAT, WOOD PULP 109 Brown Woop Pu tp. In 1862 Lyman patented a process for submitting wood to the action of water at a high temperature, 160° C. In 1870 Meyh found that when wood previously digested in this way was mechanically treated in the grinder it gave a tough long-fibred stock. Since that date large quantities of brown wood pulp have been produced for the manufacture of box boards. The wood is either simply steamed, in which case a dark brown product is obtained, or digested in water at high pressure when a lighter coloured paper is produced. Steamed Wood.—Logs of wood 12 or 16 feet long, or cut up in 2 feet lengths ready for the grinder, are packed into tall cylindrical boilers and steamed for twelve to thirty hours at a temperature varying from 120° to 160° C., the shorter period requiring a higher pressure. The water of con- densation containing organic acids and volatile compounds such as acetic and formic acids, ethereal oils, turpentine and resin is drawn off continuously, or at intervals. In modern practice such by-products are carefully preserved and refined, having considerable value. Wood Digested in Water.—A finer material of superior colour is produced when the wood is digested for twenty-four to thirty hours at a somewhat lower temperature in the presence of water, 60 lbs. pressure being the general practice. The boilers are usually cylindrical in shape, and of considerable length, erected in a horizontal or vertical position. Cast iron is regarded as more suitable, being less liable to oxidation and corrosion from the organic : i e z ' 3 bs 2 a: : ‘3 cn yoguesenenye araayerioenyrny Fig. 1 . —Digestor for manufacture of Brown Pulp. MECHANICAL WOOD PULP EEL acids produced during the operation. In Germany the practice obtains of lining the vessels with copper, and in one or two special cases digestors made of copper entirely have been built. ‘The price of a wrought-iron copper-lined digestor 5 feet diameter and 17 feet long is about £192, while a digestor constructed entirely of copper of about the same capacity would cost £450. Use of Brown Pulp.—Wood boiled in this way previous to grinding gives a material suitable for the manufacture of so-called ‘‘ leather board ’”’ used for box making. It is exceedingly tough and flexible, can be bent to almost any shape without cracking or splitting, and when made up into boxes is capable of resisting great pressure. It is also used for the manufacture of imitation kraft paper and for common paper pattern tissues. THe Estimation oF Mecuanican Woop Puup In PAPERS. The determination of the exact percentage of mechanical wood pulp in papers is obviously a matter of importance. Considerable attention has been given to this subject of recent years, and the various available methods may be briefly summarised. The use of the microscope as applied to the detection and estimation of different fibres in a sheet of paper has long been known. The first systematic application of quantitative methods to the vegetable fibres and manu- factured products is that of Vetillart, embodied in his treatise ‘‘Htudes sur les fibres vegetales textiles.’ Gottstein, in 1884, we believe, first suggested the quanti- tative microscopic method of counting the number of 112 WOOD PULP AND ITS USES mechanical wood fibres in a given field of a specimen care- fully mounted using as a test for comparison specially prepared papers containing known percentages of mechani- cal pulp. Microscopic Analysis.—The paper is broken up into pulp by preliminary treatment with a weak solution of caustic soda, which is then thoroughly removed by means of hot water, and a number of slides are mounted for inspection, Herzberg’s staining reagent being used to colour the mass of fibres. Several slides are so prepared and carefully examined. The examination is best effected by bringing every portion of the slide into the field of view of the microscope, a record being made for each field of view as to the approximate proportion in which the fibres are present. This method is preferable to that frequently employed, of absolutely counting the fibres, but it demands a good deal of previous experience with pulp mixtures in which the proportions are already known. The usual staining reagents which may be used for differentiating fibres examined under the microscope are various aniline dyes, iodine solutions and iodine combined with dehydrating agents. The most useful reagent for general work is Herzberg’s iodine and zine chloride solution. The formule for the preparation of these reagents are as follows :— Winkler Potassium iodide. . 5 grammes. Iodine. . 1 gramme. Water. : : ; BP PAD Os Glycerine same 99 MECHANICAL WOOD PULP 113 Herzberg— Chloride of zine Potassium iodide Iodine Water The colorations produced by these reagents are shown in the appended table, but the colour reaction varies with the purity of the fibre, and the percentage of moisture present in the small quantity placed on the microscope glass. 20 grammes. rg A! O'l gramme 5 grammes. Micro-CHEMICAL REACTIONS OF FIBRES. Coloration produced. Fibres. Magnesium chloride, iodine solution. Zine chloride, Iodine solution. iodine solution. Cotton, hnen,hemp| Brown Wine-red Reddish brown Esparto, straw, bamboo, celluloses Wood celluloses Manila hemp Mechanical wood pulp, jute . ; Unbleached Ma- nila, straw (par- tially boiled) Grey to grey- ish brown. Colourless. Grey, brown, or yellowish brown. Yellow. Yellow. Blue to violet, or blue to greyish vio- let Blue to bluish violet Dark yellow or greenish yellow Yellow Yellow. Bluish violet Light brown to red Yellow, green- ish yellow Yellow Yellow Colour Methods of Analysis—Various simple colour reactions are known, all of which afford a rough indication of the proportion of mechanical wood pulp in papers. In 1882, Gaedicke proposed the manufacture of a series of standard papers containing varying proportions of mechanical wood, the first paper in the series to consist W.P. 1 114 WOOD PULP AND ITS USES of pure sulphite, and the last paper of the series containing 95 or 100 per cent. of mechanical wood pulp. On each of the standand papers a solution of aniline sulphate of known strength produced a yellow coloration, the intensity of which was in direct proportion to the amount of mechanical wood pulp. Equal coloration on the standard, and an unknown paper could then be recorded as evidence of equal amounts of mechanical wood pulp, and this reaction would furnish a means for measuring the percentage of ground wood pulp in the paper. The following reagents can be employed for this purpose. Aniline Sulphate.—4 grammes of the salt dissolved in 100 c.c. of water. This reagent gives a yellow colora- tion when placed on paper containing mechanical wood pulp. Phloroglucinol.—2 grammes of phloroglucinol are dissolved in 100 ¢.c. alcohol and 50 ¢.c. concentrated hydrochloric acid added. The solution should be kept in the dark. Gives a pink to crimson coloration more or less intense according to the proportion of mechanical wood present. Ferric Ferricyanide.—Dissolve 1°6 grammes ferric chloride in 100 cc. of water. Dissolve 3°3 grammes. potassium ferricyanide in 100 c.c. of water. Equal quantities of the solutions to be mixed and used only when required. Gives a Prussian blue colour with mechanical wood pulp. Wurster’s Reagent.—2 grammes of dimethyl para- phenylenediamine dissolved in 100 c.c. of water. Gives a deep red colour with mechanical wood pulp and other lignified fibres. Phenol.—A dilute solution of phenol gives a greenish blue colour with mechanical wood pulp. MECHANICAL WOOD PULP 116 Chemical Methods of Analysis.—Ruller in 1887 suggested a method based on the solubility of cellulose in ammoniacal copper oxide. The paper, having been suitably broken up into pulp, is treated with the solution, and the cellulose dissolves fairly quickly, leaving the mechanical wood pulp as an insoluble residue to be filtered, washed, dried, and then weighed. ‘The cellulose estimations obtained by this process are not very satisfactory. The reaction of the ligno-celluloses with iodine has also been suggested as the basis of a method of quantitative analysis. ‘The paper reduced to the condition of pulp is allowed to remain in contact with a definite quantity of iodine dissolved in potassium iodide. After standing twenty- four hours the amount of iodine left in the solution is determined by titration with sodium thiosulphate, the amount of iodine absorbed being a measure of the amount of mechanical pulp present. Godeffroy and Coulon proposed a method dependent upon the reaction between lignified wood fibre and chloride of gold. The paper is torn up into fine shreds, divided into two equal portions of convenient weight, and boiled for about ten minutes in a 10 per cent. solution of aqueous ammonia, then thoroughly washed and dried. One portion is burnt for the determination of ash. The second portion is extracted with a hot alcoholic solution of tartaric acid, dried, and then successively extracted with alcohol and ether. The residue left is then boiled for about fifteen minutes with a dilute solution of gold chloride, the latter filtered and removed by washing. The dried fibre containing the adherent reduced gold is then burnt and the weight of ash and gold ascertained. The difference between the ash 1 2 116 WOOD PULP. AND ITS USES previously weighed and the weight of ash and gold together, measures the quantity of gold reduced to a metallic state, and the latter is an indication of the proportion of lgnified fibre in the sample of paper. Numerous experiments conducted by Godeftroy and Coulon show that under these conditions 100 parts of mechanical wood pulp per se will reduce 21°2 parts of gold. Benedikt proposed a method based upon the reaction between lignified fibre and hydriodic acid, the products of decomposition being added to silver nitrate, with the precipitation of silver iodide. The weight of dry silver iodide is taken as a measure of the mechanical wood pulp present. The action of chlorine gas on lgno-cellulose is also suggested as the basis of a quantitative method of analysis for mechanical wood pulp. ‘The paper is boiled in a weak solution of carbonate of soda, washed thoroughly with weak acetic acid, and then with hot water until quite neutral. The paper is pressed and exposed in a damp condition to the action of pure washed chlorine gas. After complete chlorination the excess cf chlorine gas is blown out of the vessel, and a known volume of water added to the bleached pulp. The quantity of hydrochloric acid in the aqueous solution is determined by titration with standard soda solution. The acid equivalent to one gramme of various pulps is as follows :— Mechanical wood pulp . 4°4 c.c. normal alkali Aspen mechanical pulp . 35 ce ,, fp Unbleached sulphite O76 CCares if Bleached sulphite Hes: 0376; Ce. ‘ MECHANICAL JVOOD PULP 117 The most recent method devised, by Cross and Bevan is based upon the well-known phloroglucinol reaction. A weighed quantity of the paper previously broken into pulp is placed in a solution of standard phloroglucinol, the strength of which has been previously found. The quantity of phloroglucinol in solution before and after immersion of the fibre is determined by titration with formaldehyde. It has been shown that all lignified fibres possess what may be called a constant ‘‘ phloroglucinol absorption value.” The details of the process are as follows :— Two grammes of the material are dried at 100° C. and then weighed. The weighed amount is transferred to a dry flask, covered with 40 ¢.c. of phloroglucinol solution (made by dissolving 2°5 grammes of pure phloroglucinol in 500 e.c. of hydrochloric acid of 1:06 sp. gr.), shaken and allowed to stand for some hours, preferably all night. The liquid is then filtered through cotton-wool placed in the neck of a funnel. The filtrate is next titrated, 10 ¢.c. being mixed with 20 c.c. of hydrochloric acid of 1°06 sp. gr. and heated to 70° C. Standard formaldehyde solution (made by dissolving 1 cc. of 40 per cent. formaldehyde in 500 c.c. of hydrochloric acid of 1°06 sp. gr.) 1s now added, 1 c.c. at a time, two minutes being allowed to elapse between each addition. As indicator of the presence of phloroglucinol, a piece of cheap newspaper is used. A red stain is produced in the presence of free phloroglucinol when a drop of the liquid is allowed to fall on the paper. Towards the end of the titration the stain gradually takes longer and longer to appear on the paper, and finally it is necessary to carefully dry the paper before a Bunsen 118 WOOD PULP AND ITS USES flame. The end of the filtration is indicated when the stain is no longer perceptible. 10 c.c. of the original phloroglucinol Solin are then titrated under exactly the same conditions, the amount ab- sorbed by the ligno-cellulose being obtained by the difference between the two figures. This phloroglucinol absorption value is expressed as a percentage on the dry weight of the ligno-cellulose. The following values have been obtained: Wood flour, 7°9; mechanical wood, 6°71; jute (best quality), 3°98 ; jute (average quality), 4°26; sulphite wood pulp, 0°75; and cotton, 0°2 per cent. of phloroglucinol. For the calculation of the mechanical wood in paper the. following formula is used, 8°0 being the absorption value for mechanical wood, and 1°0 that of sulphite pulp, p the absorption value of the dry ash-free sample, and H the percentage of mechanical wood in the paper. 100(p — 1:0) ee a reeay aT Sources of error, and the conditions necessary for the most constant and accurate results are :— 1. The purity of the phloroglucinol used. The standard solution is made from a weighed amount of this substance. It is therefore necessary to ensure its purity. 2. The absorption value is influenced by the concentration of the phloroglucinol solution. The quantities to be used are 2 orammes of paper and 40 ¢.c. of phloroglucinol solution. 3. Generally, it is unnecessary to remove sizing material from the paper before the determination. In the case, however, of large quantities being present, its extraction MECHANICAL WOOD PULP 119 (by warming with a mixture of alcohol and ether) is to be recommended, the reaction taking place more rapidly. EXAMPLES. Qi: Phloroglucinol | Mechanical eee c Ash. Sizing. sorvti Newspaper. Per cent. Ber ennt napa cab ate: Times . : 8°4 1°5 2°14 16°35 Daily Telegraph 2°4 15 2°40 20°0 Tribune. 10°2 1°5 5°23 60°4 Daily Graphic : 15°1 1°5 5°0 5771 4d. paper (white) . 1°5 15 6°62 80°3 4d. paper (pink) 2°0 1°5 6°32 76-0 CHAPTER V CHEMICAL WOOD PULP Tue term ‘ chemical,’ in contradistinction to the term ‘mechanical,’ is applied to wood pulp prepared by a chemical process in which the isolation of the fibre is effected by treatment of the wood with suitable solutions. The resultant product is a more or less pure form of cellu- lose, differing very materially from the fibre of the mechanical process. In the latter case the pulp consists of the raw wood in which the constituents are unchanged except in form and shape, whereas the chemical pulp is entirely different in composition from the original material. This is shown in an analysis given by Griffin and Little :— Spruce wood. Spruce cellulose. Moisture 11°5 67 Ash : : 0:3 0°5 Cellulose : 53°0 Soi Lignin, etc. . 35°2 3°1 100-0 100-0 The methods employed for the preparation of cellulose CHEMICAL WOOD PULP 121 from wood are of two kinds, namely, the acid, of which the so-called sulphite process is typical, and the alkaline, exemplified by the well-known soda process. Preparation of Wood.—Whichever system is used the preliminary operations for preparing the wood are the same. The logs are cut into lengths of two feet, the bark com- pletely removed by the methods described in the chapter on Mechanical Wood Pulp, and subsequently cut up into small chips by special machinery. For the best qualities of pulp the knots in the wood are cut out, or as an alternative the chips of wood are carried by means of a travelling band into a sorting room and all the knots and faulty pieces of wood removed by hand. Sulphite Process.—In general terms this consists in sub- mitting the wood to the action of sulphurous acid and its acid salts in closed vessels at high pressure for definite periods of time. The quality of the product can be varied to almost any extent by the conditions of treatment, that is by varying the strength of liquor, the steam pressure, and the period of time occupied in digestion. This may be shown by a study of the several qualities of sulphite pulp available for paper-making. Quick Cook Process.—This term is applied to pulp prepared by digesting the wood at a high pressure of 80— 100 lbs. per square inch for a period of eight to nine hours. If the operation is carried out to an extreme limit, using the strong liquor, a soft pulp is obtained of good colour which bleaches very rapidly with a small proportion of bleaching powder. Ifon the other hand the treatment is carried out with a minimum quantity of liquor just sufficient 122 WOOD PULP AND ITS USES to produce complete disintegration of the wood, then the pulp obtained is of a reddish colour, not easily bleached, but which is characterised by great strength and toughness. The latter kind of pulp is eminently suited for the manu- facture of news and wrapping papers, in which strength is of primary importance, whereas the former quality of pulp produced by excessive boiling is more suitable for book papers and writings in which colour is of greater importance. Slow Cook Process.—This method differs radically from the quick process, in that the pressure is seldom allowed to exceed 15 lbs., while the time of boiling occupies thirty to forty-eight hours. Moreover, the heat is applied by means of steam passed through lead coils so that the condensed steam produced does not accumulate in the digestor itself. . The pulp obtained in this case is of excellent quality and of ereat strength, being particularly adapted for the produc- tion of papers such asimitation parchments. It is frequently described as ‘‘ Mitscherlich” pulp from the name of the inventor of the process. Sulphite Liquor.—The chemical solvent used in the bi-sulphite process is a solution of bi-sulphite of lime con- taining a certain proportion of free sulphurous acid. It is prepared by burning sulphur or pyrites rich in sulphur, in suitable ovens, and passing the sulphurous acid gas obtained through tanks containing milk of lime, or through towers containing blocks of limestone moistened with water. Many different systems are in use for burning the sulphur under regulated conditions, and for producing a liquid containing definite proportions of lime or magnesia sulphites and free sulphurous acids. The proportions CHEMICAL WOOD PULP 123 vary in different mills, the following being typical of many :— Free sulphurous acid . ; . 2°03 per cent. Combined sulphurous acid . oO a Lime . : : 20:39 The quantity of sulphur required per ton of finished pulp varies from 250 lbs. to 400 lbs. Considerable attention is now given to methods by means of which the sulphurous acid gas which comes away from the digestors during the operation is utilised, thereby reducing the amount of sulphur actually required per ton. Waste Sulphite Liquors.—The waste liquors discharged from the boilers when the wood has been boiled are at present thrown away. Many attempts have been made to recover the by-products, but no system has yet been intro- duced for the recovery of the sulphur on a large commercial scale likely to be remunerative, or for the manufacture of by-products having any practical value. The problem has long been a serious one, for in 1894 a prize of 10,000 marks was offered in Germany for a prac- ticable method of preventing the pollution of streams by the waste liquor of sulphite mills, but no serviceable process has been devised. The volume of liquor is so large, that the difficulties are greatly increased. One ton of air-dry pulp gives about 2,500 gallons of acid liquor which diluted with a sufficient quantity of wash waters required for cleaning the pulp blown from the digestors is increased to about 10,000 to 12,000 gallons. Hoffmann* gives the analyses of several waste liquors as follows :-— ** Hoffmann, C., Practisches Handbuch der Papier Fabrikation, 1897. 124 WOOD PULP AND ITS USES ANALYSES OF SULPHITE PuLP WASTE LIQUOR. Total solids. Loss on ignition . Ash Total sulphur Free sulphur dioxide (SOz) Sulphite radicle (SO,) . Sulphate radicle (SO,) q Oxygen consumed 8 2°0 68°0 Grammes per litre. bo 52°0 3 4 5 85'0 93°0 92°0 69°0 81:0 — 16:0 12°0 = — — 9°2 2°9 2°6 3°8 67 Is 3°8 4°8 2°7 1°93 50°0 60:0 — The characteristic constituent of these liquors is’ the lignone-sulphonic acid (calcium salt) resulting from the specific interaction of the bi-sulphites with the aldehydic or quinonic complex of the wood or ligno-cellulose. The free lignone-sulphonic acid gives a characteristic reaction with gelatin, precipitating a colloidal viscous mass, which may be re-dissolved in weak alkaline- liquids, and when so re-dissolved has been employed in engine- sizing papers. The reaction with gelatin suggests its employment as a “tanning” agent in the manufacture of 1 Lindsay and Tollens, Annalen, 267—341; H. Seidel, Zeitschr. Angew. Chem., 1900; Suringar Diss. Gottingen, 1892; Klason. Chem. Ztg., 1897, 261; Seidel und Hanak. Mitt. Techn. Gew. Mus. 1897-—8. CHEMICAL WOOD PULP 125 leathers ; and acertain amount of the liquor is being utilised in this industry. In addition to the characteristic lignone-sulphonic acid, and excess of sulphurous acid, free and combined, the liquors contain a certain proportion of carbohydrates ; and hence after treatment of the liquors to bring about the necessary conditions, a process of fermentation is induced by the introduction of yeast, from which alcohol results. The subject of the composition and utilisation of sulphite liquors has, in fact, been extensively studied, and the following brief account of the processes patented during the last thirty years may be added. Cross and Bevan observed the reaction of the lignone sulphonates and patented the production of the insoluble colloidal compound and its use in the engine-sizing of papers. [E. P. 1548, 1883.] Mitscherlich revived the method of mixing gelatine or some cheaper form of animal size with the spent lye, in order to obtain a tannin size suitable for sizing paper in the beating engine. By using ordinary rosin size in con- junction with the new product he claimed a reduction in the cost. [D. R. P. 98,944—5.] | Ekman obtained a substance which he called “ Dextron ”’ by concentrating the liquors to 34° Be. and adding magne- sium sulphate. ‘The product was applied to the dressing of textile fabrics to render them partially waterproof and to secure them from mildew. [D. R. P. 81,643.] Dr. Frank proposed the addition of milk of lime to the waste liquor so as to separate the sulphites as calcium sulphite, the remaining liquid to be discharged as com- paratively harmless. 126 WOOD PULP AND ITS USES The presence of the large proportion of organic matter in the liquor has suggested the basis of a scheme for the manufacture of compressed fuel. Attempts have been made to concentrate the waste liquors to a syrupy con- sistency and to employ this paste in conjunction with sawdust, coal dust or charcoal for the production of briquettes. Dorenfeldt patented a modification of the ordinary calcium bi-sulphite process which appeared to make the subsequent treatment of the spent digestor lyes a more profitable undertaking. Sulphate of soda was added to the usual bi-sulphite of lime liquor, whereby a precipitate of sulphate of lime was obtained, and a solution of bi-sulphite of soda. The sulphate of lime was filtered off and sold as “ pearl hardening” for the loading of paper, and the bisulphite of soda used for digesting wood. The soda was recovered by concentration and incineration and afterwards converted into caustic soda by the ordinary methods. Drewson proposed to heat the stronger waste liquors with lime under pressure, the resultant product calcium mono-sulphite being subsequently converted into the soluble bi-sulphite with sulphurous acid gas. The cost of the process and the impurity of the regenerated liquor are conditions which have prevented the development of a likely scheme for recovery. [D. R. P. 67,889. ] Destructive distillation has been experimentally tried, but the yield of useful products is much too low. The formation of oxalic acid by fusion of the concentrated liquor with alkali has also been proved, but the quantity obtained was too small to render any operations on a large scale commercially possible. CHEMICAL WOOD PULP 127 b] a substance obtained by converting the lignone-sulphoniec acid into a soda salt, has been success- fully applied in mordanting woollen goods. Its use in this direction is naturally very limited, and offers no induce- ‘“¢ Lignorosin,’ ment to manufacture on a large scale. The utilisation of the lignone-sulphonates by treatment with nitric acid Wy the manufacture of colouring matters is suggested by the reactions of the lignone constituents of wood with nitric oxides. The treatment of these substances with nitric acid gives a series of orange and yellow dyes which produce bright shades on wool and silk. Fusion of ‘“‘lionone”’ with sodium sulphide and crude sulphur gives a sulph ir dye that colours cotton dark green, changing to 4 certgin purification of the waste sulphite liquor to eliminate the/éxcess of mineral sulphites, and a certain proportion of uble iron compounds, which produce discoloration when used in association with ordinary tanning. Considerable activity is being shown in this direction, with some prospect of success. Robeson has patented a process for tanning skins and hides in which a liquor containing a compound of sesqui- oxide of aluminium or some other base with the practically unchanged organic matter of waste sulphite liquors is employed. The lye is treated with the sesqui-oxide in conjunction with an acid capable of precipitating mineral matter from the liquor. As 25 per cent. of the solid residue in sulphite liquors ' Pollution of Streams by Sulphite Pulp Waste. E. B. Phelps, U.S.A. Geological Survey Dept. . 128 WOOD PULP AND ITS USES can be removed from solution by the hide powder test, the process seems promising. A writer in the Wochenblatt has suggested the incorpora- tion of the lyes with soap, claiming that the resinous and olucose substances present together with the mineral salt, would produce a new soap of good lathering and cleansing properties. Knosel suggests a process for mixing the sulphite lye after suitable concentration with an equal weight of phos- phate of lime, thereby obtaining a solid and soluble compound to be used as a fertiliser, the manurial qualities of the phosphate of lime being increased 380 per cent. Elb adds formaldehyde to the sulphite liquors during concentration and obtains an adhesive substance, clear and transparent, soluble in water. The formaldehyde is said to prevent the separation of salts during evaporation. Alcohol from Waste Lye.—The most recent and interesting attempt to deal with the waste sulphite liquors is seen in the experiments now being carried out on a large scale in Sweden for the production of alcohol. The process is being worked on a fairly large scale under EKkstrom’s patents at Skutskar in Sweden, the average yield of alcohol being 60 litres per ton of cellulose, no less than 54,000 litres having been produced during 1909. In 1819, Braconnet observed that, by the action of sulphuric acid on wood, grape sugar was formed, which could be fermented to yield alcohol. In 1898, Simonsen obtained 60 litres of spirit from one ton of wood by this acid process. In America, Ewen and Tomlinson, acting on the CHEMICAL WOOD PULP 129 suggestion of Classen, obtained 78 litres of spirit by the action of sulphurous acid on wood. In 1891, Lindsay and Tollens found 1°2 per cent. of fer- mentable carbohydrates in the dry solids of waste sulphite liquor, and obtained about 60 litres per ton of cellulose. ‘'wo processes have now been patented in which the lyes are first neutralised by carbonate of lime. In Wallin’s method ordinary lime is used for neutralising the liquor, and in EKkstrom’s system the waste hme sludge of the sulphate cellulose mills is employed. Schwalbe states that the neutralisation sludge obtained, after the process, con- tains sufficient calcium sulphite to effect a saving of 40 per cent. of the sulphur required for boiling wood. The volume of liquor to be treated amounts to 10,000 litres for every 100 tons of cellulose and the dry precipitate obtained on neutralising amounts to 15 tons. The liquid, after being neutralised, is cooled, aerated, then fermented for 72 hours at a temperature of 75° C., by means of yeast, and afterwards distilled. The alcohol obtained contains considerable proportions of methyl alcohol, aldehydes, furfural and acetone. It may be noted that this process, while interesting as showing the possibility of obtaining useful products from the waste liquor, does not deal with the serious problem of the prevention of pollution of streams by the discharge of the waste liquor. The direct recovery of the original sulphur has not yet been evolved as a satisfactory process. Hvaporation and combustion of the concentrated lye means a large loss of sulphur, and a method for the regeneration of the latter from organic sulphur compounds has yet to be discovered. Obviously this is the correct solution of a difficult problem, W.P. s 130 WOOD PULP AND ITS USES as it might avoid the formation of a large quantity of by-products which find no useful application in paper- making or any industrial operations. Washing and Finishing.—The pulp discharged from the digestor is thoroughly washed with water for the removal of the spent liquor, and then subjected to a careful screening in order to remove incompletely digested pieces of wood and any dirt which may be present. This is effected by screens of various kinds, all based upon the same principle, though differing in construction. The apparatus most frequently employed is the flat screen, consisting of a heavy cast-iron shallow tray fitted with brass plates which contain fine slits. The tray is kept ina state of violent agitation, so that the mixture of pulp and water flowing into the tray is also continuously shaken. By this means the pulp is easily screened, the pure material finding its way through the slits, while the coarse lesser-cooked material remains on the surface of the screen. The pulp is then sorted up into various qualities, the coarse residue being sold at a low price as “‘ screenings.” The fibre passing through the screens, being mixed with a very large volume of water, is then subjected to a process whereby the water is removed, and the pulp obtained in the form of moist sheets, containing about 50 per cent. of moisture. Sulphite pulp is usually prepared for export in the form of dry sheets, and these are produced by treating the pulp in a somewhat different manner. The wet mixture is con- verted into dry sheets by means of a machine which closely resembles an ordinary paper-making machine—that is, the CHEMICAL WOOD PULP 131 mixture of pulp and water is passed over a horizontal travel- ling wire and the thin sheet of pulp so obtained drawn through heavy rollers, which squeeze-out a large proportion of the excess water, and finally over drying cylinders heated internally by steam. Soda Process.—The alkaline treatment of wood for the manufacture of soda wood pulp is similar to that used for the manufacture of esparto pulp. The wood, in the form of small chips, is heated in large digestors with a solution of caustic soda. The non-fibrous constituents of the wood are completely dissolved, and a brown-coloured pulp is obtained. The spent liquors are preserved and the soda recovered, to be used over again as required. The soda process is one capable of general applica- tion, being utilised for woods and fibres which cannot easily be treated by the sulphite process, which latter is usually confined to the treatment of the coniferous woods. In the early days of the manufacture of wood pulp, when spruce was available in large quantities, wood pulp was almost exclusively prepared from spruce by the sulphite process. The present scarcity of spruce and the high price now ruling have compelled manufacturers to give their attention to other classes of wood, and the American Government, for example, are making investigations as to the use of woods which have hitherto been regarded as unsuitable. Such investigations will, no doubt, lead not only to the introduc- tion of woods other than spruce, pine, and poplar, but also to modifications in the various methods of treatment. All kinds of wood and other fibrous material may be converted into pulp by this process. Caustic soda combines with the acid products derived from the non-fibrous K 2 132 WOOD PULP AND ITS USES constituents of the wood until the alkali is neutralised, so - that the insoluble portion of the wood left is cellulose in a more or less pure condition, containing much less resin than the pulp obtained by the sulphite process. The practical operations are simple enough. The wood is barked in the usual manner and cut up into small pieces by the same machinery as that employed for the sulphite process. ‘The wood is digested for six to eight hours in a solution of caustic soda having a strength of about 20° Tw., at a pressure of 100—150 lbs. per square inch. ‘The con- ditions of treatment are varied according to the nature of the wood and the requirements of the paper manufacturer. For pulp that will bleach readily the process of digestion is carried out to a greater extent than for pulp which is required in the manufacture of wrapping papers. The yield of pulp and the quality are influenced by these conditions. Some interesting experiments were made by Beveridge showing the precise influence of varying factors. He made three sets of trials as follows :— Constant condition. Variable. 1. | Time and strength of caustic | Pressure varied. 2. | Pressure and time Strength of caustic varied. 3. | Pressure and strength of | Time varied. caustic ; The results were :— (1) The increase of pressure resulted in a diminution of yield, the quantity of pulp obtained being reduced considerably. OHEMICAL WOOD PULP 133 (2) The excess of caustic soda caused rapid diminution in the yield of cellulose. (3) The gradual exhaustion of the caustic soda by a pro- longed digestion prevented such serious diminution of yield. From a practical standpoint the chief consideration is the nature of the wood, and De Cew gives the following results as showing the usual conditions of treatment :— rast: Weight of air- W ees Caustic soda ape ont Yield air-dry Wood. ee ft used pcr from one pulp. = Than cord. cord. Per cent. ane Lbs. 1. Yellow Birch . 3630 641 1610 44°4 2. Soft Maple : 3520 641 1560 44-4 3. White Birch . 3190 603 1490 46°7 4, Poplar ‘ ; 2350 603 1150 49-0 5. Bass wood . ; 2325 603 1135 49-0) 6. Black Spruce. 2250 678 1000 44°5 7. Hemlock . : 2300 716 970 42°2 The variation in the quality of the pulp produced by the soda process is a striking illustration of the necessity for an exhaustive study of the whole process of chemical wood pulp manufacture. ‘The most interesting developments are seen in the suggestion that the highest yield of pulp consis- tent with the complete removal of the non-cellulose portion of the wood is best obtained by modifications in the process, which reduce the action of the caustic soda on the cellulose 134 WOOD PULP AND ITS USES toaminimum. Suggestions have been made in this direc- - tion not only with the soda process, but with all chemical methods by the idea of using wood in a perfectly dry condition; by having a vacuum inside the digestor, so that the air is largely removed from the pores of the wood, enabling the liquor to penetrate quickly; by the use of superheated steam for the boiling operation; and SO on. All these improvements are in the right direction, because the wood is not subjected to a more severe treatment, but is merely placed under more favourable conditions for the action of the caustic soda. The result of these various improvements is seen in the fact that many hard woods can be reduced to the conditions of an easy bleaching pulp in three and a half to four hours. Another instance of the value of modified conditions is to be seen in kraft papers. Kraft Paper.—The term “ kraft,’ meaning strength, has been applied to certain strong wrapping papers made by submitting wood to a modified soda process. The paper is remarkably tough, possesses a high tensile strength, and is a striking testimony to the possibilities of wood pulp as a material for making a great variety of papers. It is said that the process was discovered accidentally by a pulp manufacturer who, rather than waste some soda pulp which — had not been sufficiently digested, placed the half-boiled wood in an Edge runner or Kollergang, and reduced it to pulp by the simple process of friction. The paper finally obtained proved to be so firm and strong that the success of the new “ discovery ’’ was assured. The process, as usually carried out, involves the digestion CHEMICAL WOOD PULP 138 of the wood in a soda or sulphate liquor containing about 30 per cent. of the black lye from some previous cook. The wood is not completely boiled, but digested to a point’ at which the fibres can be disintegrated by simple friction. The undissolved ligno-cellulose acts as a useful cementing material, and the paper is bulky, light and strong. The success of the so-called “ kraft’’ papers made from soda pulp has led to the production of imitations, manufac- tured chiefly from sulphite pulps. The true kraft papers may be distinguished from the imitations by various differences in appearance and behaviour. The sulphite papers have a smooth, shiny surface when viewed in reflected light and held up on a level with the eyes, but this is only appreciated by a practised observer. The soda papers are tougher and capable of resisting a greater amount of friction, as may be proved by the well-known crumpling test. They can be twisted repeatedly without producing fracture, and this is a desirable feature in papers used for the manufacture of bags. The behaviour on tear- ing 1s generally different in the two papers, the soda being more resistant. The sulphite papers have a lower tensile strain, as a rule, than soda papers of equal weight, and also a lower _ percentage stretch or elongation under tension. These differences in physical qualities may be used as a means of discriminating between real and imitation kraft papers. It may further be noted that the natural self-colour of soda kraft papers is artificially imitated in the sulphite krafts by the use of yellow aniline dyes, which can be 136 WOOD PULPeAN Delis Uske readily extracted by means of hot water, weak solutions of alkali, or rectified aleohol. The paper after treatment is quite another colour, and this in itself is evidence of a useful character. If small pieces of the paper are pulped and boiled in a solution of malachite green, the soda paper is dyed to a much darker colour than the sulphite. When the pulp is examined under the microscope, the pitted cells in the fibres of the soda pulp contain a little nucleus of green colour, which is easily detected. This test is not of much value, since many of the fibres even of the soda pulp do not show any strongly marked pitted vessels. Soda Recovery.—In the treatment of wood and other fibres by the soda process, at least 50 per cent. of the weight of raw material is dissolved, the yield of paper pulp being about 45—50 per cent. ‘The soluble soda compounds formed during the operation are rich in organic matter, and advantage is taken of this fact to recover the soda used. The black liquors discharged from the digestor are stored in tanks, together with much of the water used for washing the boiled pulp, and then concentrated by some system of evaporation. When the liquors are sufficiently concentrated, a thick pasty mass is obtained containing a large proportion of organic resinous matter, and this on being submitted to the action of a furnace catches fire and burns. The substance is thereby converted into a dry burning mass, and after the combustion is completed the resultant material consists mainly of impure carbonate of soda. : The whole process is one that calls for considerable skill CHEMICAL WOOD PULP 137 and attention, particularly in the methods employed for utilising all the available heat. The cost of evaporation of the liquors and subsequent combustion of the black liquor is reduced to a minimum by a carefully regulated system of washing in order to prevent the accumulation of a large volume of weak washing waters, and by the utilisation of the waste heat obtained by the combustion of the organic soda compounds in the concentrated liquor. The following description of a modern recovery plant will afford some idea of the process. When the digestion of the wood or fibre is complete, the hot black lye is discharged from the digestors into storage tanks, which are usually fixed above the combustion chambers so as to maintain the temperature and prevent loss of heat. The fibrous material in the digestor is then washed with hot weak washings from some _ previous boiling, and lastly with hot clean water. The final washings only contain a small percentage of soda, and these are utilised as far as possible for a preliminary treatment of fibre from which the strong black lye has just been removed. The systems of washing vary in different mills, but the main object is the same in all cases, V1Z., a maximum recovery of the soluble soda com- pounds with a minimum volume of water. The evaporation of the black lye is effected by the use of a Porion furnace or a multiple-effect evaporator. The Porion Evaporator consists of a number of shallow pans built of brick, arranged in the form of an enclosed chamber, on the top of which are placed the tanks contain- ing the liquor to be treated. A furnace at one end supplies heat, which sets fire to the concentrated liquor in the 138 WOOD PULP AND ITS USES adjacent pan, and the heat derived from the combustion of the thick lye is utilised in further evaporation of the liquor in the other pans and chambers. The Porion is in effect an evaporator and incinerator. | The Multiple - effect Evaporator is based upon the systematic utilisation of heat and reduction of pressure in the containing vessels, in series, so as to produce maximum vaporisation effect per thermal unit. The spent liquors are pumped through a series of tubes contained in several cylindrical vessels, the tubes of the first vessel being treated externally by steam at a pressure of 15—20 lbs. The liquor passing through the tube is raised to boiling point, and on being discharged into a separating chamber gives up the steam produced. The steam so liberated then becomes the heating agent for the series of tubes in the second cylindrical vessel, and the partly concentrated liquid falling to the bottom of the separating chamber is drawn by a vacuum through the tubes of the second vessel, which are therefore under reduced pressure. ‘The process is repeated through three or four systems of tubes, in each case the steam liberated in the separating chamber being used to produce a further concentration of the liquor. An apparatus of this kind will reduce 2,000 gallons of liquor per hour, having a specific gravity of 1:050 to 400 gallons with specific gravity 1°250, evaporating off 1,600 gallons of water per hour. The concentrated liquor leaving the evaporator is dis- charged into storage tanks and then allowed to flow continu- ously into a rotary furnace. The thick lye catches fire, burns with a steady flame, and is discharged as a black mass still burning, which is wheeled away, and allowed to CHEMICAL WOOD PULP 139 char until the black carbonaceous matter has completely burnt off. Sulphate process.—First introduced by Dahl in 1883, for the treatment of straw, but now considerably applied to coniferous woods which do not soften under the soda treat- ment as the foliage of dicotyledenous woods. Sulphate of soda from which the process derives its name is of course inert, 7.e. without action upon the wood sub- stance and is added as a source of alkali, and to make good the mechanical losses in the process of recovery of the soda. This loss is approximately 10 per cent. From an analysis of sulphate liquor (see later) it is seen that there is a large proportion of sodium sulphide ; this is not added as such, but is formed by the reduction of the sulphate to sulphide in the process of recovery when the residue is ignited, this reduction being effected by the soluble organic matter in combination with soda. The sulphide has a hydrolysing action, similar in character to caustic soda, but has another function in that it has the effect of aiding the splitting of the lignone complex from the cellulose proper. ‘This dissociating characteristic is clearly seen when wood is treated with a mixture of sodium sulphide and hydrate, as against caustic alone of the same soda content. The general manufacture of sulphate pulp is restricted, for though the process yields an excellent pulp, yet the evil smelling compounds formed by the interaction of the sodium sulphide with the organic matter, limits its pro- duction to sparsely populated districts, as in Germany and Austria. 140 WOOD PULP AND ITS USES ANALYSIS OF SULPHATE Liquor. Sodium sulphate. . 87 per cent. Caustic soda. : . 24 per cent. Sodium sulphide. . 28 per cent. Sodium carbonate . : . 8 to 10 per cent. Sodium acetate . 2 to 8 per cent. Soda and Sulphite Pulps.—Although at one time the woods employed for the production of sulphite pulps were almost exclusively pine and spruce, and the soda process was applied chiefly to poplar and dicotyledonous woods, the two processes are now used almost indiscriminately for any wood capable of yielding a paper-making fibre. It is exceedingly difficult to differentiate the processes by an examination of the chemical or microscopical character- istics of the fibres or the pulp, especially when the pulps have been bleached. There are certain broad distinctions between pure unbleached soda and unbleached sulphite pulps which can be readily noted, but these are not easily detected in papers containing a mixture of the two. It is impossible to state with any certainty that a bleached soda paper does not contain sulphite pulp, though any marked deviation from qualities expected in a soda paper would indicate the presence of sulphite pulp. If the soda pulp has been made from poplar wood, it is easily detected, and the admixture of any spruce may be approximately determined, but if the soda pulp has been made from spruce, no satisfactory analysis is possible. The differences between soda and sulphite pulps, even when prepared from the same type of wood, may be found in the physical qualities, since the soda pulp is of a light CHEMICAL WOOD PULP 141 brown colour, soft and bulky, and very tenacious, while the sulphite pulp is reddish white, harsh, strong and less bulky. The presence of a much larger percentage of natural wood resin in sulphite pulp, namely, 0°5 per cent., as against 0°05 per cent. in soda pulp, can be used as the basis of a test, but it is of no value for sized papers. A small quantity of the pulp is heated continuously with carbon tetrachloride. The solution placed in a fresh test tube is mixed with an equal volume of acetic anhydride, cooled, and added to a few drops of concentrated sulphuric acid. With soda pulp no definite reaction occurs, but with sulphite pulp a pink coloration changing quickly to green is produced. Tort BLEACHING OF Woop PuLp. Two methods are in use for the bleaching of wood pulp, the most general being the employment of ordinary bleach- ing powder, and the secord being the treatment of the pulp by means of solutions of hypochlorite of soda or magnesia prepared by electrolysing the chlorides. This method of electrolytic bleaching is finding general favour amongst manufacturers when the power required can be supplied at a cheap rate. Bleaching with Chloride of Lime.—The general principle of bleaching wood pulp by means ofa clear solution of ordinary chloride of lime is simple and fundamentally a process of oxidation. ‘The method consists in immersion of the pulp in a given quantity of diluted bleach liquor of definite strength, but many modifications of method are available, and need to be closely studied in order to produce 142 WOOD SRUEP FAN DST Ss Sisto the best results economically. The various systems in use may be briefly described. Bleaching in the Potcher. — This is the process most generally adopted by the paper-makers. The sheets of dry pulp are put into the potcher with water, broken up, and a definite volume of clear bleach liquor is added. The pulp is continuously circulated until the desired colour has been obtained, or until the bleach has been completely exhausted. When the operation is completed, the pulp is washed con- tinuously with fresh water, the exhausted bleach liquor and washings being removed in the usual way by means of the drum washer. In many cases the pulp is discharged into large tanks provided with perforated false bottoms and the washing process completed by draining. Bleaching in Drainers.— A modification of the above process which gives good results is frequently used. The pulp is broken up in the potcher, the requisite amount of bleach liquor is added and the contents of the potcher at once discharged into tanks where the bleaching process is allowed to proceed with the mass at rest. This method requires longer time, but gives excellent results in point of colour and economy of bleach. Bleaching by the Tower system.—FYor this process of con- tinuous bleaching a series of cylindrical vessels with taper- ing bases is used, about 16 to 20 feet high and 84 feet in diameter. The stuff is kept in circulation by means of a pump fitted at the junction of the tapering ends with an external pipe, the latter being so arranged that the circulating stuff can be pumped into the tower or to the adjacent one of the battery. Fitted in the upper part of the tower is a cone, arranged THE BLEACHING OF WOOD PULP 143 centrally with, and almost touching, the sides of the outer cylinder to ensure thorough distribution of the stuff, as it is pumped up the external pipe (see lig. 19). It is usual in a modern battery of bleaching towers to pass the stuff as it comes up from the potcher through a concentrator in order to remove a large proportion of water whereby the bleaching is carried out more economic- ally and expeditiously. In series with the last bleaching tower also there is a Fic. 19.—Tower Bleaching Plant. This photograph on a reduced scale represents a plant capable of bleaching 10 tons of half stuff per diem. second concentrator, which removes the residual bleach liquor to a great extent, the necessary washing being reduced thereby to a minimum. This machine is very simple and compact, and capable of a large output. It is on this account to a certain extent replacing the more costly presse-pate system of purification. It consists of a revolving drum made with a central internal cone, so as to deliver water at both ends. The shell itself is of brass, drilled with holes and covered with a wire cloth. The stuff is pumped up through a butterfly throttle valve [dae WOOD PULP AND ITS USES into a splaying mouth, thus causing the pulp to flow along the whole width of the drum cover. The cover or hood is so arranged by means of packing, that the water in the half-stuff can be forced through the wire cloth of the revolving drum, by a pressure of 2 to 8 lbs. per square inch, leaving a mat of fibre upon it. The pulp is then picked off the wire by means of a jacketed couch roll, and a wooden doctor fitted to the latter serves to scrape off the fibre into boxes. An economy of about 25 per cent. in the bleach consumption over the ordinary method employed with a minimum of power is claimed by this system. The total time occupied in bleach- ing is usually about twelve hours without heat. Automatic Process. —In many wood pulp mills the ‘“‘tower’”’ system is so contrived as to produce a con- tinuous automatic bleaching of the pulp. The pulp dis- charged from the digestors is thoroughly washed and then pumped into a series of large cylindrical vessels, so arranged that a continuous stream of pulp and water enters the first vessel together with a carefully regulated quantity of bleach liquor which also flows into the first tank at a constant rate. The mixture gravitates into the second vessel of the series, then into the third, and in this way throughall the vessels, until on reaching the last tank the bleach is fully exhausted and the pulp has attained the desired colour. The bleached pulp is then removed and thoroughly washed. Conditions for Economical Bleaching.—Ilt is difficult to accurately compare the methods adopted by paper-makers in bleaching wood pulp for the purpose of determining which system gives the best results, but there are certain conditions common to all methods. THE BLEACHING OF WOOD PULP 145 In the first place, the bleaching powder must be of good quality, containing the specified percentage of available chlorine. The extraction of the soluble calcium hypo- chlorite also needs careful attention, as serious losses fre- quently occur when the powder is not properly exhausted. With chloride of lime containing 35 to 36 per cent. of available chlorine the quantity of clear bleach liquor obtainable for various densities is shown in table :— TABLE SHOWING THE NUMBER OF GALLONS OF BLEACH LIQUOR OBTAINED FROM 1 Owr. oF PowbER (34 TO 36 PER CENT. OF CHLORINE). i Een Tie tpes Vou ecticnat | 0s per conte powders [86 per ean, powder 20 61:50 61:2 66:0 19 58:40 65°3 69-0 18 55°18 69-0 73-0 07 52-27 13°5 17:0 16 48°96 11-7 82:5 15 45°70 84:0 88°25 14 42°31 90-0 97°5 13 39°11 98°3 104-2 12 35°81 106-4 112°5 ii 32°68 1165 120°5 10 29-61 129-0 137:2 9 26°62 142:0 151°5 8 23°75 160°3 169°7 7 20-44 186°1 197-2 6 17°36 219°5 232-4 5 14:47 264-0 278°6 4 11:44 334-0 352°5 3 8-48 448-2 475°5 2 5°58 681-0 722°6 1 2°71 1403-0 1488-0 " 1:40 2725°0 2883°0 Any deviation from the above figures may be traced to an unnecessarily prolonged agitation of the powder with water W.P. L 146 WOOD PULP AND ITS USES or an imperfect washing of dregs. Fifteen minutes is sufficient to produce a liquor of maximum density with a residue which settles readily ; if the operation is continued, as it often is, for an hour or more, the insoluble residue becomes bulky and does not settle quickly. The result is that the first strong liquor cannot be so completely siphoned off from the residue. The best plan is to exhaust for fifteen minutes, allow the sediment to settle completely, siphon off as much as possible, and to agitate the residue for another fifteen minutes with fresh water, adding the weak liquor when clear to the first extract, so as to give a stock bleach liquor for use in the mill at a density of 6° Tw. The dregs are again exhausted with water and the weak liquor so obtained utilised in exhausting the next batch of powder. It should also be noted that fresh liquors cannot be kept indefinitely in store tanks without deterioration. The unstable nature of solutions of bleaching powder, and the loss of available chlorine entailed when the liquor is not used under proper conditions, is well known to most paper-makers, although such depreciations in bleaching value are not always expressed in numerical terms. The following experiment will throw some light on the character and extent of the changes found in ordinary bleach liquor, when stored. Some fresh bleaching powder was taken, and a solution made by extraction with distilled water, having a strength of 7° Tw. Three samples of liquor were put aside under the following conditions :— A. Sample of clear liquor in stoppered bottle. B. Sample of liquor in an open vessel, and left exposed, THE BLEACHING OF WOOD PULP 147 the crust of chalk which quickly formed on the surface being left undisturbed. C. Sample of liquor in an open vessel, agitated twice a day, at 9 a.m. and 4 p.m. These solutions were tested once a week, with a standard decinormal solution of arsenic. TABLE SHOWING C.C. oF ARSENIC SOLUTION REQUIRED BY 1G¢.C. oF THE BuEacH LIQUOR. Period. topieral Open Eea Open vessel, bottle. not disturbed. agitated. At start . : : 7:05 7:05 7:05 After 1st week : 6:90 6°90 3°90 onde Awa. 6°85 6:60 0:40 ae ort 6°8 4:0 0:27 eros, 6°8 2°7 0-16 In the case of the bleach liquor preserved in a bottle and kept away from contact with air, the loss of avaiiable chlorine is very slight. In the open vessel, where the formation of a crust has prevented continual contact with air, the reduction of strength is slight the first two weeks. Probably the rapid fall in the later weeks of the period may be due, in some measure, to the disturbance of the crust in removing samples for titration. In the case of the solution agitated each day the loss of strength is very rapid. The precise value of these changes are readily seen by reference to the accompanying tables, in which the losses are set out. L 2 148 WOOD PULP AND ITS USES TABLE SHOWING AVAILABLE CHLORINE IN 100 C.C. OF THE BLEACH LIQUOR. A. B. C. Grammes. Grammes. Gramunes. | At start . F ; : 2 5() 2°50 2°50 After 1 week . ; ; B45 2°45 1°38 , Q2weeks. . . 2-43 2°34 0°14 ae aes 2°40 0:96 0°05 Expressing these results in a form more familiar to paper-makers—that is, in terms of the weight of normal bleaching powder—we get the following :— TABLE SHOWING THE AVAILABLE CHLORINE EXPRESSED AS LBS. OF NORMAL BLEACHING POWDER PER 100 GALLONS. A. B: C Lbs. Lbs Lbs At start . : ; 70°5 70°5 70°5 After 1 week 69°0 69:0 39°0 » 2 weeks : ; 68°5 66°0 4-0) Ne a 68°0 27°0 1°5 The storage of the bleach liquor in the paper mill usually resembles the conditions of experiment B, and it will be noticed that the depreciation for the first week is very slight indeed. THE BLEACHING OF WOOD PULP 149 The principal chemical change brought about by exposure to air is the disappearance of calcium hypochlorite and the increase in the percentage of calcium chloride, con- current with the formation of a considerable amount of chalk, more particularly with the sample agitated each day. Use of Residual Liquors.—The practice sometimes adopted of utilising residual liquors washed out of the potcher on the completion of a bleaching operation cannot be generally recommended. ‘“‘ Back liquors ” may be reported as containing “ available chlorine” in useful quantity from the density as tested by the hydrometer, in conjunction with the occasional applica- tion of the usual chlorine test solution, viz., starch paste and potassium iodide. ‘The latter test, however, has no quantitative value, and the usefulness of the hydrometer as an indirect indicator of chemical strength depends upon the correct interpretation of density. Direct chemical tests are alone able to reveal the actual condition of the back liquors. | Circumstances under which residual liquors could be used with any advantage are to be found in mills where water is scarce. In such cases the pulp from boiling opera- tions might be treated with the residues for the purpose of using up any traces of bleach, and also economising washing waters. Composition of Residual Liquors.—The liquors left after the bleaching of wood pulp are of a complex composition, They contain soluble organic compounds, resinous matters. lime salts, residual hypochlorites and salts of higher oxides of chlorine (acids), ¢.g., chlorites and chlorates. 150 WOOD PULP AND ITS USES Temperley gives the analysis of such a wood pulp liquor as follows :— Lbs. per 1,000 gallons. Mineral residues, chiefly calcium chloride 126°6 Organic residues, volatile on ignition ep) Total solids, dried at 100° C. . 188°6 The surface scum obtained from the liquor had the following composition :— Lbs. per 1,000 gallons. Resinous matter : : ; oo MOE Lime. : . . : : 4 ‘80 Moisture . 3 ; ; . 8:90 Fibre : : : : 2 .. 240 Total ; ute The compounds in solution in residual liquors are very unstable, and react easily with the hypochlorite of fresh bleaching powder, so that the employment of washings in conjunction with raw bleach solution must result in a waste consumption of powder per ton of air-dry pulp. Temperley has shown this by some interesting experi- ments, and we quote these as illustrating an important factor in economical bleaching. Definite quantities of bleach solution were added to known volumes of ordinary water, and similarly to equal volumes of a carefally filtered residual liquor from the bleaching of a sulphite pulp. The THE BLEACHING OF WOOD PULP 151 solutions were tested for a period of four hours at different temperatures, the results being very different in character. EXPERIMENTS WITH ORDINARY WATER. Bleaching powder used. Solution. Temperature Grains per Lbs. per 1,000 used. gallon. gallons. Water 70° Fahr. 4°20 0°60 AS OO mae 4°90 0°70 120° _,, 9-10 1:30 EXPERIMENTS witH ResipuaL Liquors. Bleaching powder used. Solution. Temperature Grains per Lbs. per 1,000 used. gallon. gallons. Liquor 70° Fahr. 194-20 27°70 “. SLU 248°50 35°50 e IPA i 784:00 112°00 The figures here show that residual liquors, even if colourless, are positively detrimental to efficient bleaching. Practical work demonstrates this, not only from the point of view of consumption, but, what is often of greater importance, from the point of view of colour. The same defect is found to a lesser degree in the use of unfiltered water, or water coloured by vegetable matter in solution. It is evident, therefore, that the practice of using residual liquors should be confined to their use for partial washing, and that they should not be used for diluting strong bleach liquors. There are many interesting and important details to be noted in connection with the bleaching of wood pulp. The process is frequently hastened by the use of live steam, which is blown into a mixture of pulp in the potcher. The 152 WOOD PULP AND ITS USES rate of bleaching is thus considerably hastened, but the practice is not one that should be carried to an extreme. The economy of bleach is also controlled to some extent by the proportion of water to pulp. In some cases the number of pounds of air-dry pulp per gallon of liquid is much lower than it need be, and this usually tends to a greater consumption of bleach powder. The usual proportions are :— Air-dry wood pulp . : . 100 lbs. Amount of solution in potcher 160 gallons. The bleaching of very hard sulphite pulps not manu- factured originally for bleaching may frequently be assisted by slight modifications in the process. A refractory pulp may often be bleached to a good colour by the operation known as ‘‘ successive bleaching.” ‘The pulp is treated with a certain proportion of bleach liquor, which is then washed out and followed by a further quantity of fresh bleach liquor. This method is often sufficient to remove the yellow tinge found in half-stuff from poor qualities of pulp. Caustic soda may sometimes be used with advantage as a preliminary process in bleaching hard pulps which exhibit a reddish colour, but it is not economical to bleach “ low boiled” pulps, as the bleach consumption is too great, sometimes reading 30 per cent. [ven simple washing with hot water before bleaching gives a pulp of greatly improved colour. The improvements due to preliminary washing may be traced to the presence of soluble constituents, the nature of which is at present unknown. That these constituents THE BLEACHING OF WOOD PULP 153 exercise a considerable influence on the bleaching may be seen from the following experiment :— PuLP BLEACHED FOR THREE Hours AT 70° FanrR. Conditions of bleaching. ip Seen eae oe Colour. Pulp bleached in the ordinar y mee ina shallow dish . 10°8 Moderate. Pulp bleached in the ordinary way in a bottle . : 10°8 PA Pulp bleached after ‘being first ex- tracted with water ; 12-0 Good. Pulp bleached after extraction with water followed by ether 76 Very good. The ‘time element” is an important factor in many mills owing to the lack of adequate bleaching plant, which in many cases can be attributed to the fact that the output of paper is increased by additional machines, but that this is not accompanied by the installation of further plant for the preliminary operations. Some pulps bleach quickly and readily, while others occupy a much longer time. It is not, of course, possible to determine whether a pulp will bleach easily by mere superficial observation; this can only deal with the associated characteristics of the pulps. The rate of bleach consumption is a close index of general bleaching quality, and the following experiment is of inte- rest as showing the differences between pulps which do not exhibit any great differences when simply judged on external characteristics :— Haperiment 1.—Brand C. An ordinary soda wood pulp. 50 grammes air-dry pulp with 450 c.c. bleach liquor at 65° Fahr. (containing bleach solution equivalent to 11'7 grammes of dry bleaching powder). 154 WOOD PULP AND ITS USES Experiment 2.—Brand B, », 4,016 kilos chlorine = 7,500 kilos. 9 ”9 1 ton chlorine aL salt. 1 « Papermaker’s Monthly Journal,’ May, 1910. THE BLEACHING OF WOOD PULP 1g)! The following table has been given to show the cost of power and salt for one kilogram active Chlorine. Cost of power Cost of salt Cost of power No. Price per litre. for 1 kg. active for 1 kg. active and salt for 1 kg. chlorine. chlorine, active chlorine. Sa GE d, d. d. 1 1 4 1°42 0°72 2°14 phe Mis 2°85 0°72 ood 1) aL a7 0°72 6°42 2 1 4 15 0'S64 2°164 lez 2°6 0°S64 3°464 We a°2 O-S64 6:064 5) 1 4 1-2 1:08 2°28 1 2 2°4 1:08 3°48 ite a 4°8 1:08 ass 4 1 4 1165 1-44 2°09 I 2 2°30 1-44 oi4 as eal 4°60 1°44 6°04 The Siemens and Halske apparatus is so constructed that the products of electrolysis, namely chlorine gas and caustic soda, can be separated continuously during electrolysis, and when so desired caused to interact outside the electrolyser for the production of bleach liquor direct. The makers claim that by this means the same amount of active chlorine can be produced with lesser power and with a smaller pro- portion of salt, and state that the power consumption is 3°5 to 4 k.w. hours for each one pound of active chlorine. It is obvious that a plant capable of producing bleach and soda in this way possesses many advantages over those forms of apparatus in which only bleach lquor is produced. In localities where lime is plentiful and cheap, and where caustic soda finds a ready market, the Siemens and Halske electrolyser should give economical results. Taking the figures above quoted with the apparatus utilised only for 172 WOOD PULP AND ITS USES the manufacture of bleach liquor, the cost of one ton of active chlorine would appear to be as follows :— Quantities. Price. Total. £ Seg) Soke. | Power . : . |5,090 k.w. hours | at ¢d. per unit! Ose) Salt : d ; 7°5 tons at 12s. ASLO Renewals : : = say Oc 0a Interest and other charges. —-- say bre Oee0 <1 1 Game 1 The unit is a kilowatt hour. Schuckert's Electrolyser.—This apparatus consists of cells similar to those employed in other electrolysers, the chief feature being the special form of the electrodes. In the Siemens and Halske apparatus the electrodes are con- structed of platinum and iridium, while in the Haas and Oettel they are provided with electrodes made entirely of eraphite. In Schuckert’s electrolysers the positive electrodes are made of platinum and the negative electrodes of graphite. This arrangement 1s based upon the fact that the carbon electrode is not attacked by the electro-positive element at the negative pole, and the platinum is not acted upon by the electro-negative compounds present at the positive pole. Several advantages are claimed for this arrangement, as not only does the apparatus require less frequent renewels, but the presence of smaller particles of carbon in the liquid is avoided. ‘This electrolyser appears to be capable of provid- ing strong solutions of bleaching liquid. With a 10 per cent. solution of salt a bleaching liquid containing 15 grammes of THE BLEACHING OF WOOD PULP 173 active chlorine per litre can be obtained with an energy consumption of 3°2 kilowatt hours and a supply of 5:4 Ibs. of salt per lb. of chlorine. The usual limit is 20 to 22 erammes of active chlorine to the litre, and with a Schuckert electrolyser 30 to 85 grammes per litre can be obtained. Some interesting experiments have been made bv Dr. Fraass with electrolytic bleach liquor prepared by the Schuckert apparatus.t The cellulose examined was easy bleaching sulphite pulp. A weighed quantity of the pulp was mixed with water and a definite proportion of bleach liquor (a) from chloride of lime and (b) from electrolytic bleach liquor. The temperature of the operation was maintained at about 80° C. until the whole of the chlorine had been consumed. The results of this test are given as follows :— CoMPARISON OF BLEACHING EFFECTS OF (a) CHLORIDE OF LIME AND (6b) ELecTRoLyTiIc LYE. Pulp Active chlorine | Chlorine used fe Osco I crtames pea | eramnionat Resulting white, : litre. air-dried pulp. a b a b 1 Lela 0°67 | 0°67 | 2°00 | 2°00 | Same with both. Za 20 1°25 | 1:25 | 1:99 | 1-99 | Better with electrolytic lye. 3 1312;7 | 0°80 7-0°80 |-2-00 / 2°00 fe + ae OO eUs ORO bd Lalo? Aeles2 a 5) Deli? a 0-50 0780 2°02- |) 2°02 is 6 deste OU ymeO 60 Yee 0042-00 ie teeta 27) 80-79-0079 122-00 |) 2-00 if | 8 1:20 LOO e100 5 2-00 e) 2°00 - 9 1220 150° 1-50 1.3°00:}, 3°00 Fie | 10 i120 TOO A004 200-6200 Tt le20 L009 2:00 4) 72"00 +1 2°00 3 12 hea) 1°50 | 1°50 | 3°00 | 3°00 e ' For further details see ‘‘ Papier Fabrikant,” 1909. 174 WOOD PULP AND ITS USES Further experiments were made by Dr. Fraass to deter- mine the actual saving of chlorine, if any, effected by the use of electrolytic chlorine. The following results were obtained. (a) REFERS To CHLORIDE OF LIME; (b) REFERS TO ELECTROLYTIC LYE. elt) Bal el Se ae Lge No. Sora ee Grarees per Pr ence of jin per cent. Better white with. litre. air-dried pulp. | Chlorine. a b a b 14 Pa 1:0 150995 ie 202m 199 1°45 b. 16 1; 20 3°00, | 2°99 0°90 | 5°40 1:90 b. 18 L218 AZT ade 23 2°06 | 2°00 2°90 b, 20 1:16 1°29 | 1°24 2 UGG 1299 3°40 b. 22 1320 2°24 Wee 4°54 | 4°34 4°40) b, 24 20 2°27 | 2°15 | 4°54 | 4°30 5°26 | aand b same. 26 1:12°5 | 0°89 | 0°80 2°21 | 2°00 10-0 a. 28 1F220 1:00 | 0°90 2:00 | 1°80 10°0 a, 30 Let 2F 0 SO gO re. 2:00 | 1°80 10°0 a. From the foregoing brief account of electrolytic bleach- ing systems it would appear that evolution on the basis of experience has limited these systems to the production of a solution of a hypochlorite which is used upon the pulp or cellulose textile to be bleached, and is then rejected as a waste liquor after the bleaching agents are exhausted in doing chemical work upon the pulp or fabric. The idea of an industrial cycle as advanced by Hermite is rendered impossible by the fact, which is too often over- looked, that with the bleaching or oxidising action there are secondary reactions, as a result of which organic products pass into solution. These products will consume oxygen until reduced to compounds of the lowest molecular weight. This of course is entirely waste work. THE BLEACHING OF WOOD PULP 175 The electrolytic systems finally evolved are therefore intermittent, and the rejection of the waste solution involves a loss of so much salt which is too dilute a form to be use- fully recovered. When we come to the question of the direct production of caustic soda and chlorine, we arrive in the region of “heavy” chemical industry. As a result of inventive evolution there are two systems finally established in this country, which are those of Castner-Kellner, and Hargreaves-Bird. Each of these systems produces chlorine as such, which is converted into bleaching powder, or bleaching liquor, as an ordinary chemical operation outside the electrolytic system. As regards the work of the cathode, or soda end of the process, the Castner-Kellner system produces caustic soda owing to the special disposition of its electrode, whilst in the Hargreaves-Bird process the soda which is produced as caustic soda is removed in the form of carbonate. These well-established systems, for the production of alkali and “ bleach,” are not easily engineered, and they are in many respects unsuitable for small production. The matter with its technical and commercial issues is much too complicated to be usefully discussed within the scope of this work. Many problems are presented which are as yet by no means solved and it is quite possible that the over-pro- duction of chlorine, which is an incidental feature of these systems, may lead to further developments of the industrial production of cellulose on very different lines from those which are exploited to-day as almost stereotyped. 176 Imports oF Woop PULP INTO GREAT BRITAIN, WOOD PULP AND ITS USES 1904—1908. (From the Annual Statement of Trade of the United Kingdom). QUANTITIES. 1904. 1905. 1946. 1907 1908. oes Dry. Tons. Tons. Tons, fons. Tons. I’rom Russia -| 9,033} 12,179 | 11,698) 13,558 7> 157501 » sweden . 131,655 |133,564 |127,046 |157,916 |163,074 NOT wa ya 09,213 | 63,948 | 77,047 | 70,957 | 77,665 , Germany 5,609 | 7,186| 7,584 | 15,514 | 23,687 ,, Netherlands 2,131 | 2,622] 25595 | 3; 280 seme ,, Portugal 2,115} 2;482°) "(2,219 | 2 4d Ga , Austria Hungary 2,183.|° °3,163 |. ‘1,765: 4,3050 aie owe ,, United States of Aanecics L188.) 2.917) 92,69 le O42 855 , Other-Foreign Countries 862 349 707 300 212 Total from Foreign Countries /211,139 |228,410 |233,352 |270,188 286,860 Total from British Possessions 953 | 2,964) 7,297 753| 1,795 Total oa ele) 931,374 240,649 [270,941 |288,655 CHEMICAL, WET. Tons. Tons. Tons. Tons, Tons, | From Sweden 7,112) 6,948) 7,261 | 13,295 1)916,310 SiN Ofwa ye. ; “17,6(3.) AVAIL 4) 9,109 | a eae Pemother Foreign Countries 10 As 10 Total from Foreign Countries 24,785 18,075 16,370 99.164 | 27,296 Total from British Possessions : . ae (Canada) 19 950 Total 24,785 | 18,094 | 16,370 | 22,314 | 27,296 MECHANICAL, DRy. : Tons, Tons. Tons. Tons, Tons. From Russia 33199) 42,776 | 1,999)" 08 7a ae » sweden . 2,984 3,922) 1,986) 2.4287) 3-510 a Norway 2,811} 3,553 | - 2,733 2,593 2,192 ,, Other Foreign Countries 154 16 | 11 10 Total from Foreign Countries| 9,148 | 10,267) 6,669) 6.069| 8,073 Total from British Possessions (Canada) Bl 1,453 Total 9,199 | 10,267 6,669.) 6,069) 97626 IMPORTS OF WOOD PULP INTO GREAT BRITAIN 177 9? 9 QUANTITIES. 1904. | 1905. | 1906. 1907. 1908, Mrcu ANICAL, WET. Tons. Tons. Tons. Tons. Tons. From Russia 0,452 | 2,614] 1,686] 2,899; 2,608 » sweden _| 30,741 | 32,940 | 31,212 | 43,610 | 46,019 ENG ae | /224,620 (202,249 229,202 |262,256 277,988 5, Germany : : : 25 20 a 645 799 Other Foreign Countries (ie: 182 64 220 Total from Foreign Countries |260,912 |238,010 |262,164 [509,630 |327,414 From Canada . : f 62,957 | 80,236 | 80,959 | 63,545 | 95,548 | Other British Possessions 31 Se 2 oh Totel from British Possessions | 62,957 | 80,267 | 80,959 | 63,545 | 95,543 | Total . (823,869 |818,277 348,123 |373,175 422,957 (ee a Se ee ee CHAPTER VI NEWS AND PRINTINGS. THE applications of wood pulp, though large and of first- rate industrial importance, are not numerous. Its utilisa- tion, however, in paper-making is essentially one of great influence, and in point of fact this industry at the present time dominates the wood pulp market. In this country there have been several well-marked phases of expansion of the industry. A prominent landmark was _ the repeal of the duties on paper in 1860. By a coincidence this indirect condition of expansion synchronises with the introduction of esparto grass to develop rapidly into an important staple raw material, almost a generation in advance of the wood pulp age. By the year 1880 the importation of esparto had reached 200,000 tons, and it is a somewhat remarkable feature of this industry that the consumption of esparto has shown no growth from this fioure. The wood pulps have been independently developed. “Mechanical” wood pulp or ground wood dates back to the period 1850—60. The chemical pulps in this country were pioneered by C. B. Ekman in collaboration with George Fry in the period 1870—80. ‘This early venture was capitalised by Thomson, Bonar & Co., and worked at Bergvik, Sweden, and Ilford, Hssex. The new industry attracted other pioneer NEWS AND PRINTINGS 179 workers, notably E. Partington in this country, and C. Kellner in Austria, who individually and jointly did much to establish the new order during the following decade. It requires a little calculation to estimate the growth of the industry during this period, 1880—90, since the statistics of importation, in the Board of Trade returns, are a complex return including ‘“‘ Esparto and other Materials”: it was not until 1888 that the returns of wood pulp importation were separately recorded. The growth of the wood pulp trade from 1880 to 1888 represents an estimated quantity of 100,000 tons, and at this later date the industry had become widespread and firmly established in Scandinavia, Germany and America. The English importation has continued to grow, and the figures for the first nine years of the century may be cited :— ’ The total world’s production of “chemical pulp.” is fast approaching 3,000,000 tons. In taking this statistical view of the paper industry we may note the figures arrived at by Krawany, for paper consumption per head per annum, in Kuropean countries :— Keg. Ke. Kg. England . 25°3 Belgium . 111 Russia er? Sweden . 240 Holland .10°8 Greece ease: Finland . 22°56 Italy . ie ior hare i? 128 Germany .19°7 Denmark . 64 MRoumania. 1°4 Norway . 163 Luxemburg 4°8 Bulgaria . 1:3 Switzerland 15:0 Spain. . 44 Bosnia Ae USL France .140 Hungary . 3°6 Servia U0 Austria . Ili: Portupale.. 3°4. Another result of this statistical inquiry is the ascertained annual increase of the world’s production, which at 53 per' N 2 180 WOOD PULP-AND ITS USES cent. is nearly double the estimated increase of other large manufactures, viz., 23—84 per cent. These figures are taken from an interesting paper by Dr. A. Klein on ‘Cellulose, Wood Paper, Artificial Silk,” recently published (Chem. Zeit., 60, 521-—580 (1910) ). | The most significant development in the paper-making art and industry founded on wood pulp is in the production of ‘‘news,’ and we may take ‘‘ News and Printings” as the subject of this chapter, and typical, in fact, of the industrial age we live in. The enormous quantities of mechanical and chemical pulp manufactured to-day are used chiefly in the production of “news” and cheap printing papers. A modern newspaper contains about 70 per cent. of mechanical pulp mixed with 80 per cent. of chemical pulp. In addition to the fibrous constituents the paper will also contain about 8 to 10 per cent. of china clay, and a small proportion of rosin size. As far as the paper mill is concerned, the process of manufacture is almost entirely an engineering problem, since all the materials used are purchased largely in a completely manufactured state, the object being to eliminate chemical processes whenever possible. This is only true of paper mills dependent on outside sources for the supplies of pulp and chemicals, but the tendency of modern practice in such mills is to reduce the question to one of mixing certain ingredients and getting the maximum output of paper at a minimum cost. At the same time chemistry plays an important part in the efficient and economical working of a ‘‘news” mill. NEWS AND PRINTINGS 181 From start to tinish every process is controlled by analysis, while improvements in the quality of the paper are gradually introduced, either by the use of superior wood pulps, or by suggestions that arise from a careful study of the systematic records kept. A general survey of the operations necessary for the production of this class of paper will show the intimate relation between chemistry and engineering in almost any industrial process. Power.—The amount of coal consumed averages 18— 20 cwt. per ton of finished paper. Most of this fuel is required for motive power, though a certain proportion is used in drying the paper during manufacture. The steam engine is employed for this in nearly every paper mill, but in a few cases gas engines worked from gas producers have been tried. The maintenance of an extensive boiler plant on up-to- date principles demands the control of the coal supplies in the matter of weight received, the analysis of same for moisture, ash left on combustion, and calorific value; the systematic analysis of the waste gases from the boiler flues to prevent careless firing of the boilers, and to ensure com- plete combustion; the use of suitable water for boiler purposes, involving the utilisation of all condensed steam and hot water, and the adoption of some efficient process for softening any hard water which must be employed in addition. All these operations are controlled by simple methods of chemical analysis. The theoretical value of a given coal supply having been found by analysis, and expressed in terms of the heat units available, it should be possible to 182 WOOD PULP AND ITS USES determine what proportion has been expended in useful work, the particular stage in the manufacture of the paper at which each proportion has been utilised, and finally what amount has been wasted. Questions of this kind are of great importance, and involve measurements of many factors. Chemicals.—F rom what has been said as to the nature of the operations involved in the manufacture of the modern newspaper, it is evident that the number of chemicals properly so called is not very large. Amongst them will be found rosin and alkali used for sizing, or some form of prepared size; china clay used as a loading; lime for the water-softening process; alum and sundry colour- ing matters and pigments; acid and bleaching powder ; starch, ete. | Oils and greases required for lubricating purposes, and other supplies connected with economical power, also need attention at the hands of the analyst. Wood Pulp.—The exact control of the supphes of pulp is an important part of the duty of the mill chemist. The determination of the air-dry weight of every consignment of pulp is sometimes regarded as a mechanical and simple task, but it is one of considerable responsibility. All pulps, whether delivered in a dry state or in the moist condition, require to be tested for moisture. Chemical pulps are tested regularly for quality, satires larly as to their behaviour with bleach. Some pulps are very difficult to bleach, and consume a large amount of bleaching powder. In many cases where a white pulp is required a ready bleached pulp is used, but this plan is not economical since it is cheaper to treat the pulp at the paper mill than to buy the material already bleached. NEWS AND PRINTINGS 183 Mechanical pulps vary in quality and freedom from coarse fibre. The differences in bulking qualities are very marked and may be measured in the laboratory on small samples readily. Paper.—The examination of the finished paper from the machines in regard to its physical properties of strength, bulk, finish and sizing is a matter of routine in a well- ordered mill. The testing of contract samples in respect of actual composition to determine the percentage of load- ing, the proportions of mechanical and chemical pulps present and the existence of other fibres, as well as the usual physical tests mentioned, is a necessity when making papers to sample. There are many items in manufacture which call for the exercise of careful and painstaking research on the part of the chemist, and when these technical questions are studied exhaustively by him under the needful encouragement of the authorities, the information gradually accumulated is of the greatest value. The systematic correlation of modifi- cations in manufacture, with the improvements in the finished paper by proper classified records which can always be referred to, is perhaps one of the most important points, but one which is almost neglected in the average mill. IMPROVEMENTS IN THE MANUFACTURE oF CHEAP NEWSPAPER. During the last twenty-five years great progress has been made in the production of common paper from wood pulps. The contrast between the old and new methods is best illustrated by reference to the output of a machine. When wood pulp was first used there were few machines 184 WOOD PULP AND ITS USES capable of making a sheet of paper more than 120 inches wide at a speed of 200 to 250 feet per minute, with an average production of 50 tons per week. ‘To-day the modern machine will produce a sheet of paper 170 inches wide at a speed of 500 feet per minute, with an output of nearly 45 tons per day. Preparation of the Beaten Pulp.—The proper proportions of mechanical and chemical pulp are first disintegrated by treatment in large potchers or special machinery, being mixed with a suitable quantity of water, or generally with waste waters from the paper machine. The mixtureis then transferred to a beating engine capable of holding sufficient wet material to produce one ton or more of dry paper, and beaten for about thirty or forty minutes. This is a process far removed from that which obtains in the treatment of rag, when the beating engine giving the best results is only capable of holding wet stuff equivalent to 1 to 2 ewt. of dry pulp, and the operation is only completed after eight or nine hours. To the mixture in the engine about 10 per cent. of china clay calculated on the dry weight of pulp is added. Rosin size to the extent of 1 or 2 per cent. is then thoroughly incorporated, and alum added to precipitate the size which adheres to the fibres. The pulp is suitably dyed to the desired colour by means of pigments or soluble aniline colours. The subject of the beating of pulp is one of great technical importance, since the quality and characteristics of a paper are easily altered by modifications in the process of beating. In an elementary treatise of this kind it is impossible to enter fully into the question, and only a brief indication NEWS AND PRINTINGS 186 can be given of the variations which are obtained as a matter of daily routine. The main object of the beating process is the proper isolation and reduction of the individual fibres after the raw material has been sufficiently boiled and bleached. There Fig. 22.—The “ Holiander” Beating Engine. are many types of machines available for the purpose, but all constructed on the same principle, namely, the circu- lation of the mass of pulp and water in a narrow trough provided with a revolving beater roll which, as it rotates, acts upon the mass drawn between the knives of the roll and a set of knives fixed on the bottom of the trough. The general construction of an ordinary “ Hollander ”’ 186 WOOD PULP AND ITS USES beater is shown in the diagram. ‘The engine consists of an oval-shaped vessel divided into two channels by a “ mid- feather’ or partition fixed along the centre of the vessel, but not extending completely to the ends. In this way the oval vessel is divided into two channels. An adjustable beater roll, which is a solid cylindrical drum fitted with knives projecting from its surface, rotates in one of the channels and revolves above a set of knives projecting from the bottom of the trough. The engine is filled with the re- quired amount of pulp and water, and by the rapid rotation of the beater roll the mixture is constantly circulated round the troughs of the engine and passes continuously between the knives on the beater roll and those which are stationary. The fibres are thus completely separated and gradually reduced. The varied effects produced in beating wood pulps may be illustrated by one or two examples. ‘Thus, if soda pulp is beaten quickly with sharp knives, the beater roll being close down on to the stationary knives, then a soft spongy paper resembling blottings is produced. If on the other hand, a strong sulphite pulp is beaten slowly for a long time—eight or nine hours—the knives being blunt, and the beater roll being lowered gradually during the process, then a close dense sheet of paper, strong and resembling parchment, is obtained. In the latter case the curious assimilation of water by the fibre takes place, with a production of an imitation parchment paper. Probably the beating operation is the most important in the various stages of the manufacture of paper, on account of the great variations which are possible by altering the conditions under which the pulp is beaten, NEWS AND PRINTINGS 187 It is customary in mills where the ordinary type of ‘‘ Hollander’? is used to pass the beaten stuff through a refiner, whereby the fibres, which are more or less inter- locked by the beating, are brushed out. The types of refiners mostly used in this country are the ‘ Marshall” and the “ Jordan.” The Fourdrinier Paper Machine.—The pulp after beating is ready for conversion into paper. It is discharged from the beating or refining engines into large reservoirs or stuff chests, of which there are two to each paper machine. The contents of one chest are supplied to the machine while the second is being filled from the beaters, so that the pulp is uniform and ensures the manufacture of a regular sheet of even weight and thickness. The pulp flows through a number of strainers which serve to retain any coarse pieces of pulp and other impurities. For the fast-running news machine the strainer is a hollow eircular drum, the shell of which consists of a series of curved brass plates bolted together, each scored with fine slits. ‘The drums revolve slowly and are kept in a state of violent agitation, so that the fine pulp passes through the slits and the coarse material is retained. The mixture of pulp and water flows in a continuous stream on to the surface of an endless ‘“ wire.”’ This consists of a wide band of wire gauze stretched horizontally over two rolls, known technically as the “breast roll” and “couch roll.” The stream of pulp is carried forward at a rapid pace, the water finding its way through the meshes of the wire, and the fibres settle down on the surface of the wire cloth interlacing or ‘felting’? with one another. Further quantities of water are removed from the pulp by vacuum strainers or 188 WOOD PULP AND ITS USES boxes fixed under the wire near the couch roll, and the “web” of paper then passes between the couch rolls which compress the fibres, remove a certain proportion of water, and give firmness to the sheet of wet paper. The most recent innovations which have been introduced to facilitate an increased output of paper and at the same time an improvement in the strength of the sheet, have for their object devices for increasing the speed of the paper machine. Amongst these may be mentioned the ‘ Hibel”’ method of manipulating the machine wire. Under this system the wire cloth upon which the pulp flows is inclined at a considerable angle from the breast roll to the couch roll so that the material flows downhill, so to speak. By this simple device it is possible to obtain a rapid flow of a very dilute mixture of pulp containing large quantities of water, which latter is easily removed owing to the slope of the wire cloth. Another improvement is the substitution of a vacuum couch roll in place of the ordinary solid roll hitherto employed, thus obviating the use of a top couch roll. The wet sheet of paper passes over a large roll, part of the surface of which as 14 revolves is submitted to the action of a powerful vacuum, so that the excess of water is removed from the wet sheet of paper. The fibres are felted together and the life of the wire cloth is prolonged. The web leaving the couch rolls is drawn through two or more sets of press rolls, which serve to compress the fibres into a firm adherent sheet. The wet sheet of paper then passes over a number of drying cylinders, which are heated internally with steam. In the earlier machines eighteen to twenty such cylinders amply provided all the drying surface necessary, but in the NEWS AND PRINTINGS 189 modern paper machine thirty-two to thirty-six cylinders are required to dry the paper completely, owing to the largely increased output. The drying of the paper is an important item, because it is desirable to dry the paper as slowly as possible at a com- paratively low temperature. When the number of cylinders is limited, a much higher temperature is necessary to ensure complete drying of the paper, but in such case, while the output of finished paper can be maintained, the strength of the sheet is seriously diminished. The paper is afterwards passed through calenders in order that a surface or finish may be imparted to it. The ordinary calenders fixed at the end of a machine used for the manufacture of news consist of a number of highly polished chilled rolls, and the paper in passing over and under, these rolls is further compressed and at the same time glazed. No further process is necessary for ordinary news, but the reels of paper produced at the end of the machine are re- reeled and cut into the required lengths and sizes. CHAPTER VII WOOD PULP BOARDS LarGe quantities of mechanical wood pulp are used for the manufacture of pulp boards which have many industrial uses such as for boxes, packing cases, cards, calendars, advertisement goods, pienic dishes and a variety of similar articles. In some cases the pulp is mixed with stronger fibrous material such as jute, hemp, and chemical wood pulp, particularly for boxes of high quality which are required to withstand rough usage. The heavy stout boards frequently used for railway carriage panels are made from the best materials and by hand or manual process, the sheets being produced on moulds similar to those employed in the manufacture of hand-made papers. The cheapest qualities of thin boards, of which an ordinary tram-car ticket is a typical example, are produced on the continuous-board machine, which in general construction resembles the ordinary Fourdrinier or paper machine. For certain grades of pulp boards which cannot be made on the continuous-board machine, on account of the thickness, a simpler form known as the single-board machine is used. | The chief advantage of a wood-pulp board as contrasted WOOD PULP BOARDS | 191 with the common strawboard, which it has superseded to a large extent, are to be found in its more attractive appearance, its cleanliness, and above all its bulk, being thick and of light weight. Moreover it has less tendency to erack when folded or bent, and when covered with coloured paper, the colour does not fade as frequently happens with strawboards which have not been carefully made. The traces of alkali often present in common straw- board produce a decided fading of some aniline dyes. Single-board Machine.—Mechanical wood-pulp boards of any desired thickness are produced in sheets of definite size on this machine. It differs very lttle from the wet press used in the manufacture of wood pulp itself, and only a brief note of its construction need be given. The pulp mixed with the requisite volume of water is passed over strainers which remove coarse chips, and pumped continuously into a large wooden vat, containing a hollow cylindrical drum revolving at a slow rate. The surface of the drum consists of fine wire gauze, and as the drum revolves, the pulp adheres to the surface in a regular and uniform laver or skin, while the water passes freely through the meshes of the wire. The layer of pulp comes into contact, as it passes out of the water, with a travelling felt, and adhering to this, is carried away from the vat and drawn between two heavy rollers, which squeeze out the excess moisture. As the thin sheet of pulp is wound up on the upper roller, it forms a sheet of mechanical pulp which gradually increases in thickness, and when the desired thickness has been reached the sheet is immediately cut away from the roller and put aside. ‘The travelling felt passes round the lower roller 192 WOOD PULP AND ITS USES and back to the vat containing the mixture of pulp and water. The process is continuous, and the sheets obtained are then submitted to pressure, thick felts being interposed between the sheets of pulp so that the water drains away completely. The material in this condition then contains about 50 per cent. of dry pulp and 50 per cent. moisture. The sheets are dried, glazed, and cut to any required size, the final thickness of the boards being determined by the pressure applied during the process of glazing. Continuous-board Machine. —This is a combination of the single-board machine and the ordinary paper-making machine, and is used for making “ duplex’’ and “ triplex ” papers. The beaten pulp is formed into thin sheets in two or more vats, and these sheets are brought together between rollers so as to produce one sheet of the required thickness. The board then passes over a large number of steam-heated cylinders, and completely dried. The dry board is also glazed and finished by calenders fixed at the end of the machine, and finally cut up into sheets. No further operations are necessary, the finished board being manufactured and completed by the one machine, the processes following one another automatically. Machines of this kind are frequently fitted with more than two vats, and in such cases some of the vats are filled with common waste material, while two are filled with a high-class well-bleached pulp. In this way, a good board can be produced cheaply, consisting of a low-grade middle, covered on either side with a paper of good quality. The colour of the outer surfaces of the board can be varied. WOOD. PULP BOARDS 193 Box-MAKING. The great demand for boxes as a convenient substitute for brown paper in the wrapping and packing up of goods has resulted in the creation of an important industry. Raw Materials.—The boxes are manufactured from straw- boards, wood-pulp boards, and “leather” boards. The nature of the composition of the raw material may generally be gathered from the descriptions applied, though the term “leather boards” is somewhat misleading. Many of the so-called boards are made from various kinds of specially prepared wood pulp, but in some cases a small proportion of leather clippings is incorporated with vegetable fibres by suitable treatment. The cheap flimsy folding boxes used for wrapping medicine bottles and similar temporary purposes are made from common board which contains little more than waste paper. The boards are brittle and do not stand much folding. The leather boards, on the other hand, are wonderfully strong and tough, capable of being bent and twisted into all kinds of shapes. Classification—The different kinds of boxes made in large quantities from the raw materials described may be classified as follows :— (1.) Plain square-shaped boxes, with corners pasted, and finished off with plain or ornamental paper. (2.) Square-shaped boxes, corners wire stitched. (3.) Square-shaped boxes, with metal-edged corners. (4.) Folding boxes. (5.) Round boxes, made up or stamped. (6.) Tubes and small cylindrical cases. W.P. a) 194 WOOD PULP AND ITS USES Plain Board Boxes.—The boards are first cut into convenient sizes, on an ordinary cutting table worked by hand, or in a rotary millboard cutting machine worked by power. In the rotary machine a large board can be cut up into a number of strips of the required length by means of circular knives fitted on to the shaft of the machine, which knives can be adjusted to any desired degree of accuracy. The strips obtained from the cutter are afterwards reduced to the required width. The square pieces of board are next scored, that is to say, slight cuts are made on the board where the sides are bent up to form a box. If the pieces of board are not scored in this way they crack and break when bent into the form of a box. Machines are also employed in which the cutting and scoring are carried out simultaneously. After the boards have been scored the corners are cut out by simple stamping machines and the box at once made up. The operator bends over two edges of the board to form a right angle, and places the corner thus formed in a stamping press which presses down a small piece of gummed paper of the proper length round the corner fastening the two edges together. This operation is repeated four times in the making of the boxes. The lid of the box is manufactured in a similar manner, due allowance being made in the cutting of the board in order to obtain a well- fitting lid. The boxes are left plain, or finished off with printed labels and ornamental paper. The covering of boxes with ornamental paper is a simple process, the variations being not so much in- the methods employed as in the materials used. Most of the boxes used WOOD PULP BOARDS 195 by drapers are generally covered with a flint-glazed box paper, the edges of the boxes being finished off with coloured paper of a similar character. The edges of the boxes are first covered with thin strips of paper either by hand or by machinery, the top and sides of the box being afterwards covered with the white glazed paper in such a manner as to leave the coloured edges of the box exposed. Boxes produced in this way in large quantities are finished by means of a “banding’’ machine in which a reel of slazed paper is gummed on one side and drawn on to the box which is automatically turned four times by the machine and thus covered. Wire-stitched Boxes.—The board used for this class of box is cut into required sizes and either scored or dented. In the latter case the board is passed through a denting machine which stamps a slight depression along the line which is to form the corner of the box. The ends of the board are then slotted so that the box can be produced by being turned up into shape along the lines formed by the denting machine. The ends are then fastened together by. the wire stitching, in which process small pieces of wire are forced through the ends of the box and clinched. Metal-edged Boxes are generally manufactured from good material, such as leather. boards, because they are intended for constant use. The boards are usually grooved along the bending line, either with a square groove or with a deep V-shaped groove, the latter being preferred as giving the box a neater finish at the corners when completed. The edges of the box and the joints are finished off with 0 2 196 WOOD PULP AND ITS USES metal edging which consists of a thin strip of metal stamped out and provided with sharp projecting points. When this strip is forced into position the projections pass through the board and being turned up by the machine are firmly clinched. ‘The boxes made by this process are very strong and present an attractive appearance. Folding Cases.—The cheap common cases used for packing eggs, patent medicines, and similar articles of domestic use are stamped out from thin cardboard by machinery. The general shape and outline of the boxes having been calculated, a metal forme or template is prepared, by means of which the outline of the box can be stamped out. The forme resembles in principle that used by a printer, but instead of raised type, strips of brass are used and also pieces of hardened steel. When the thin board is placed on the forme and submitted to pressure, the brass strips indent the board along the lines which are to form the edges of the box, and the steel knives cut out the portions of the board which are not required. The two edges which overlap to form one side of the box are fastened together with wire stitching or with glue. In this condition the box can be folded flat, and when required for use it can be opened up and put together as a box very quickly. Postal Tubes, ete-—The many varieties of cylindrical boxes made for postal work, the packing of gas mantles, phonograph records, carbon paper, blue print and photo- graphic papers, and similar purposes, are made by covering one side of a board with glue or some adhesive material, and rolling the board up into the form of a tube on an WOOD PULP BOARDS 197 iron roller, the diameter of which varies according to the size of the bore of the tube. | For short boxes the long tubes are cut up into stated lengths. The caps for these tubes are stamped or pressed out of circular discs of flexible leather board. The whole operation is exceedingly simple and does not seen: any elaborate explanation. CHAPTER VIII THE UTILISATION OF WOOD WASTE Vanrous methods of utilising wood refuse are in practice, chiefly based on chemical processes. The only commercial application of waste wood based on a simple mechanical treatment, and now an extensive industry, is the manufacture of wood wool. Wood Wool.—This is an elastic material much used for stuffing cushions and mattresses; for packing glass, hard- ware, and fragile goods; for filtration, and many other purposes of diverse character. It is very light and bulky, not easily reduced in volume when wetted, and is thus eminently suited to these and similar uses. Any small odds and ends of wood from carpentering and cabinet workshops up to 14 or 16 inches long can be utilised. Special machinery has been devised for converting pieces of wood of all shapes and sizes into shavings of desired thickness. The pieces of wood are fed to the machine by hand. They are seized by rollers which carry the wood forward automatically, bringing them under planing irons and also in contact with pointed knives, the thickness of the shaving being determined by the setting of the plane irons and the width of the shaving being fixed by the position of the knives which produce cuts in the wood parallel THE UTILISATION OF WOOD WASTE 199 to the lengh. One machine is capable of producing 6 to 12 cwt. of wood wool in twelve hours. Sawdust.—Large quantities of sawdust are produced in many industries, and the profitable utilisation of this waste material depends largely upon the quantity periodically available. When the amount is small, it is best utilised as an ordinary packing material, but for this there can only be a limited demand. Some idea of the varied uses of saw- dust may be gathered from the following brief description of the methods in use. :, Sawdust thoroughly mixed with common rosin is con- verted into fire-lighters. Mixed with highly concentrated artificial manures, it serves as a medium for manurial purposes. The sawdust itself has no value as a fertiliser, but it has a capacity of absorbing and retaining liquids. Occasionally the sawdust is first converted into charcoal. Sawdust has also been employed as the source of the carbon in calcium carbide. The sawdust is first converted into charcoal, which is mixed with limestone, and the mixture heated for several hours in an electric furnace. In limited quantities, sawdust is also converted into paper pulp, but the fibre is exceedingly short and of little value, and it is difficult to obtain an evenly boiled material owing to the difficulty of maintaining a proper circulation of the caustic soda, lye, or other reagent in the digestor. Sawdust is also mixed with the concentrated waste liquors from the sulphite wood-pulp manufactories, and then converted into briquettes. These briquettes can be used as fuel or submitted to distillation for the manufacture of wood spirit, acetic acid, and charcoal. 200 WOOD PULP AND ITS USES Producer Gas from Wood.—An interesting application of the use of waste wood is to be found in the generation of ‘“‘ nower gas.’ In Riche’s gas-producer the wood is heated in two suitable retorts, one of which is used for the distilla- tion of the wood, and the second for the decomposition of the gases obtained by the distillation of the wood in the first retort. The combustion is first started in the second or reducing retort. When the heat has been raised to the proper extent, the distillation is commenced in the first retort. The charcoal produced is withdrawn periodically from the bottom of the first retort and thrown into the reducing retort. The distilled gases from the first retort are passed through the heated charcoal placed in the second, and subsequently into the gas holder. The gas produced has a heating value of about 340 B.T.U. per cubic foot, the quantity of gas per 100 kilos. of wood being 100 cubic metres, or about 16 cubic feet of gas per pound of wood. Donkin * states that about 100 small plants of this type have been erected in France and some of the French colonies. An interesting example is to be found in Madagascar, where gas obtained in this way is utilised in two gas engines of 15 and 8 h.p. respectively for the manufacture of artificial ice, the cost of the motive power being one-third of that obtained by usual methods. . Oxalic Acid.—Sawdust and other forms of wood waste yield oxalic acid when treated with caustic soda. Forty parts of sawdust are mixed with strong caustic soda of specific gravity 1°35, and heated in shallow pans until the temperature rises to 220—240° C. The product contains 1 «Gas and Oil Engines.” 3B. Donkin. THE UTILISATION OF WOOD WASTE 201 carbonate of soda and sodium oxalate. This is dissolved completely in boiling water, and the strength of the solution carefully regulated, so that on cooling, the sodium oxalate erystallises out. The mixture is then treated in the hydro extractor to remove the liquid. The crystals of sodium oxalate are dissolved and treated with milk of lime, and thereby converted into calcium oxalate. The latter product is precipitated, separated from the liquor by filtration or any suitable means, and repeatedly washed with water. The calcium oxalate is then decomposed by treatment in a lead-lined vessel, with strong sulphuric acid, the whole mixture being heated with steam, and maintained at the boiling point for some time. The oxalate is decomposed, giving, after treatment with the sulphuric acid, a precipitate of calcium sulphate and a solution of oxalic acid. The precipitated calcium sulphate is removed, and the solution carefully evaporated for the production of crystallised oxalic acid. The amount of oxalic acid obtained may be varied according to the method of heating. Thus the percentage yield is increased by using potassium hydrate as well as sodium hydrate, and also by heating the material in thin layers. The yield of oxalic acid from various woods is as follows :— Spruce. 94°7 Poplar ; 93°0 Beech.-~ . 86°3 Oak . ; 84-4 202 WOOD PULP AND ITS USES Tur Destructive DISTILLATION oF Woop. When wood is burnt under conditions which restrict the supply of air, or heated in closed retorts, it passes through a process of destructive distillation with the production of certain valuable commercial substances. The combustion of wood in a confined space was resorted to in early days for the manufacture of charcoal simply, and large quantities of this charcoal are produced even to-day by the primitive method of stacking wood, covering it with earth and setting fire to the wood at the bottom of the pile. The only substance obtained was the charcoal left when the process was completed, but about 1812 the discovery of the presence of wood spirit and acetic acid in the vapours given off, led to a closer study of the chemical changes taking place. | The products of distillation are chiefly acetic acid, wood spirit (methyl alcohol) tar, gases and charcoal. By slow distillation at a low temperature a maximum yield of acetic acid and tar is obtained. The gas given off during the operation, a mixture of carbon dioxide and carbon mon- oxide, is utilised by passing it through the furnace employed in heating the retorts. The carbon dioxide is reduced to monoxide, a combustible gas which gives off its available heat in the furnace. By rapid distillation at a high temperature, the volatile products are decomposed giving a greater yield of gas and a smaller proportion of acetic acid. The effect of the method of heating is shown in the following table taken from Fischer’s Chemical Technology. In the slow distillation process, the wood was heated slowly THE UTILISATION OF WOOD WASTE 203 for six hours, starting with cord retorts, while in the fast distillation the wood was placed at once in heated retorts and treated for three hours. Percentage yield of distillation products. Wood % pure : Wood. distillate. Tar. Aa Oy | peas shivenad Pe Birch— slow . 51°05 5°46 45°59 5°63 29°64 Toe fast . 42°98 3°24 39°74 4°43 21°46 30°06 Beech— slow . 51°65 5°85 45°80 ed. 26°69 21°66 fast 44°35 4:90 39°45 3°86 21:90 30°10 Oak— | slow : 48°15 a210 44°45 4:08 34°68 il Taste: 45°24 3°20 42-04 3°44 20°10 27 'Ua Larch— slow os “ig Wen | 9°30 42°31 2°69 26°74 21°65 fastes.: <3 43°77 5°58 38°19 2°06 24°06 a2° 17 | Spruce— SLO Ses 46°92 5°93 40°99 2°30 34°30 | 18°78 fast . 46°35 6°20 40°15 178 24°24 29°41 In practice the distillation of wood is carried out with due regard to the nature and quantity of the desired products, and the method of treatment varied accordingly. Steam Distillation. — With pine and woods rich in turpentine oils the material previously reduced to the condition of small chips is heated by means of steam in closed vessels at a pressure of 40 lbs., and the oils distilled off by the steam. This process is usefully employed in the pulp mill, since the manufacture of paper pulp from pine wood can be con- ducted in such a way as to ensure the extraction of the turpentine from the digestors and the subsequent conversion 204 WOOD PULP AND ITS USES of the wood into pulp. The soda process of paper-making is easily adapted, for the ordinary steam pressure is sufficient to drive off all the volatile oils, and most of the resinous matters are converted into soluble soda compounds. Dry Destructive Distillation.—The products obtained from different woods as determined by the Bureau of Chemistry, Washington, are shown in the following table :-— Average yield per cord of wood (128 cubic feet piled wood). , Resinous Hard wood Hard woods. woods. sawdust. | Charcoal (bushels). ; 45 30 30 Crude wood spirit containing acetone (gallons) . ; 10 Acetate of lime (lbs.) : ; 75 120 60 | Tar (gallons) : : : 15 Wood oil (gallons) — Turpentine (gallons) — In the slow distillation process, a maximum yield of solid product is aimed at, with a minimum quantity of gas. Harper gives the results of a test on dry yellow pine :— Yield per cord, air-dry. Gallons. lbs. os Turpentine. : ; 18°64 134°20 3°679 Wood oil , , ; 11°09 86°50 oS 14 Pars A : ‘ : 96°0 846°72 23°216 Acid : : 2 : 96°0 830°49 DIET Cake ; . : ; — 14°74 404 Charcoal . ; — 796:00 21°826 Yellow oil and pitch A 6°78 57°02 1°563 Gas and Loss . : , — 881°33 24°170 3,647°0 100°000 THE UTILISATION OF WOOD WASTE 205 With the rapid distillation method, a maximum yield of eas is obtained, and in this case the process is utilised for the manufacture of illuminating gas or for power gas. All kinds of waste wood material such as sawdust are turned to good account in this way. CHAPTER IX TESTING OF WOOD PULP FOR MOISTURE In the selling and buying of wood pulps the question of associated moisture is of obvious importance, regulated by convention and by standards, it requires to be controlled by actual tests. The mechanical wood pulps are generally shipped from the mills in the form of bales containing moist pulp on the basis of 50 per cent. air-dry pulp. The chemical pulps are shipped usually in bales containing the air-dry pulp. Disputes frequently arise as to the exact air-dry weight of pulp received, the chemical pulps frequently containing moisture in excess of the standard, and the mechanical pulp also containing a larger amount of moisture than 50 per cent. No satisfactory standard method has yet been found for the sampling and testing of wood pulp. When the freshly made bales are shipped from the pulp mill so that the whole of the sheets in the bale are uniform, then it is comparatively easy to take samples from the bale which shall fairly represent the pulp. If, however, the distribu- tion of moisture in the bale has been altered to any extent, either by loss in weight owing to the drying of the outer sheets and exposed edges of the bale during prolonged TESTING OF WOOD PULP FOR MOISTURE 207 storage, or on the other hand if the bales have become much heavier by accidental wetting through rain or other causes, then the sampling is by no means an easy matter. Frequently the water in the bale freezes, and in conse- quence of this much of the water is drawn from the interior of the sheets and deposits itself as a layer of snow or ice between the sheets which lie upon one another in the bale. The bale when opened falls apart most readily just at those points where the surface of the sheet is covered with ice, and it is almost impossible under such circumstances to take out samples that shall fairly represent the whole bale. Jiven when this ice has thawed out sufficiently to resume the form of water, it does not distribute itself evenly through the pulp for a very long period. General Principles.—A certain proportion of the bales which form a consignment are selected for the test. Usually 4 per cent. of the number of bales are taken, due care being exercised in the selection so that the bales are sound, in good condition, and do not exhibit any serious deviations in gross weight. The selected bales are weighed and sampled. The samples as cut are immediately put into bottles, or tins, which are sealed up and taken to the laboratory where they are dried at a temperature of 160° C. and the percent- age of absolutely dry pulp determined. The weight of air-dry pulp is calculated from this figure on the arbitrary basis that 90 parts of absolute dry pulp give 100 parts of air-dry pulp. The analyst gives a certificate in accordance with the following schedule :— 208 WOOD PULP AND ITS USES Woop Putpe Moisture CERTIFICATE. (Form adopted by the British Wood Pulp Association.) THis 1s TO Crertiry that I have tested for moisture a parcel of Pulp, said to consist of bales, marked lying at The samples were drawn by me on ; ; Bales. T. Cwt. Qrs. Lbs. Total gross weight of bales sampled (intact) (For numbers and detailed weights see below.) Weight of Parcels calculated from above . Percentage of absolutely dry pulp in the sample ; 5 : : per cent. moisture in the sample . d * air-dry or moist pulp in the parcel on the basis of 90=100 (air-dry) . i 45=100 (moist) . ip excess Moisture, Fibre . T. Cwt. Gan Lbs. Weight of Pulp to be invoiced . NUMBERS AND DETAILED WEIGHTS OF BALES SAMPLED. Analyst. Difficulties in Sampling.—tIn practice it is found that the testing of wood pulp for moisture offers many difficulties. The uniformity of the moisture throughout the bale is seriously disturbed by the causes already described so that not only is it difficult to select really representative bales, but the work of cutting out samples is also complicated. Various methods are employed for taking out samples of pulp, and at present there is no standard method, although attempts have been made to establish a uniform system. TESTING OF WOOD PULP FOR MOISTURE 209 It is scarcely necessary to enter into any prolonged discussion as to the merits of the various methods each of which are no doubt correct under certain conditions. With pulp that has not been in stock more than three or four weeks any reasonable system would give correct results, but the difficulty is to find a system which woukl give correct results on freshly made pulp and exactly the same results on the pulp after having been in stock several months. Probably the system which finds general favour is that known as the “‘ wedge” method, in which it is assumed that a wedge having its apex at the centre of the sheet of pulp and a base of any desired width at the outer edge of the sheet of pulp represents the sheet itself, taking the correct proportions of the inner and outer sections of the sheet. ‘This may be explained by reference to the diagram in Fig. 23. Let ABCD represent a sheet of air-dry pulp of uniform thickness, measuring 24 inches by 18 inches, and divided into four equal parts—H, the inside portion; H, the outer portion ; and F, G, intermediate portions, thus :— Square inches. Area EK = AP So LOD Areas HK, F SLO UO relent ee ——_ ALOU Areas E, F, G As OD Xe ee bOoe— 524-0 Ayoas tune. Pha Dare X13] = 432°0 Square inches. K =:-108 a Ais: G7 108 rie 108 Total== "432 WOOD PULP AND ITS USES Rn ee nee ne Ol en eens " Ag-s2----— = H - = 24 23. Fic. ile Sele ees Fig. 23. TESTING OF WOOD PULP FOR MOISTURE 211 The dimensions of the various rectangles are all propor- tional, that is, the ratio of the length to the breadth is the same in all cases, viz., 24 to 18. A sample from the sheet which shall represent the whole is obtained by taking equal areas from each of the pieces EK, F, G, H; but in practical testing such a course is impossible, as it would necessitate marking the exact position of the “lines of separation” before the small pieces of equal area could be cut. Another alternative would be to cut a quarter sheet from the whole—an equally impracticable scheme. But a wedge gives four equal-sized pieces from the four areas H, I’, G, H. Let such a wedge having a base of, say, 2 inches, be drawn as shown in Fig. 23. Let Fig. 23a represent the wedge on an enlarged scale, consisting of the four areas e, f, g, h. The area of the whole sheet is 24 inches by 18 inches, or 432 square inches, and the areas of the wedge is that of a triangle whose height is 9 inches and whose base is 2 inches. The wedge contains a series of triangles, viz., (1) the triangle e; (2) triangle consisting of pieces e f; (8) triangle consisting of e, f, g; (4) triangle consisting of pieces e fg h. By calculating the area of each triangle the exact size of the separate pieces e, f, g, h is found. The height and base of each triangle is easily cal- culated :— (1) Base of triangle e Height of triangle ef Base of triangle (efgh) Height of triangle (efgh) Base of e 46 = — giving 1:0 inches. 2 9 212 WOOD PULP AND ITS USES (2) Base of triangle ef Height of triangle ef Base of triangle (efgh) Height of triangle (e¢fgh) Base of ef —- 6865 — = - giving 1°4144 inches. 2 $; The other triangles are treated in a similar manner and the areas readily calculated. (Area of a triangle = 4 base x height.) Square Inches. Triangle hgfe has area 4 (2 X 9) io yh KZ eb eea(1s7815 <7 1925 ea HL ye e(1:4144 X-6°365) — eo ee: Fee uh ees) — 9°25 From the above figures the areas of the pieces e, f, g, h, are :— Square Inches. €—— 220 fp Spay. Og ——e2l20 i RS Hence any sized wedge contains what the pulp maker defines as correct proportions of ‘‘ inside and outside pulp,” at any rate mathematically. Absolute Dry and Aw-dry Pulp.—The exact air-dry weight of pulp is calculated on the basis that 100 parts of air-dry pulp consists of 90 parts absolute dry pulp and 10 parts of natural moisture. This is an arbitrary figure based on the assumption that air-dry pulp contains 10 per cent. of natural moisture. As a matter of fact the air-dry weight of pulp varies according to the conditions of the TESTING OF WOOD PULP FOR MOISTURE 213 atmosphere, but for trade purposes the arbitrary figure selected is convenient. In 1896 Sindall made some experiments with a view of determining the influence of the atmospheric moisture upon the weight of wood pulp. Numerous samples were exposed to ordinary atmospheric conditions for nearly two years, the samples of pulp being weighed two or three times a week and the relative humidity of the air being also noted. The following table was compiled as the result of these experiments, showing the air-dry weight of the exposed pulps, the actual absolute dry weight of pulp being 88 parts in each case. | SHOWING THE, VARIATION OF THE WEIGHT OF PULP DUE TO MOISTURE IN THE AIR, ee pan Mechanical Pulp. page Soda Sulphite Pulp. Average. Average. Average. o1°4 99°03 95°98 96°53 60°00 100°04 96°42 96°85 65°30 100°42 96°91 97°45 taeeU 102°24 98°60 99°30 80°15 102°41 98°21 99°50 82°10 102°78 98°41 99°74 82°70 102°58 98°70 99°69 82°90 102°84 98°78 99°80 83°20 103°56 98°95 100°50 83°90 103°17 98°98 100°68 85°10 103°81 99°42 100°60 86°60 105°138 100°41 101°638 87°50 104°55 99°92 101°04 §8°24 104°64 100°23 100°93 89°10 104°63 100°02 101-14 90°00 105°40 100°70 101-90 93°00 106°82 102°40 103°76 The exact relation between the humidity of the air and the air-dry weight of wood pulp as determined 214 WOOD. PULP AND ITS USES by these experiments may be expressed in the following Ooms | | If the numbers representing humidity form a series in arithmetical progression, then the weight of wood pulp corresponding to those numbers produces a series of figures in geometrical progression, thus :— Humidity = H, H + d, H + 2d, H 4+ 3d, H + 44d, Weight = W, Wr, Wr’, Wr’, Wr, Where digress, If the results given in the table are plotted in the form of a curve, it is possible to correct the errors of observation and determine the air-dry weight of pulp for every 5 degrees difference in the humidity of the air. SHOWING THE VARIATION OF THE WEIGHT OF PULP FOR EACH 5 DEGREES INCREASE IN THE HUMIDITY OF THE AIR. Air-dry Weight of Pulp. Relative Average Humidity. ; difference Constant r. H. Mechanical. a ae and Sulphite. for bi. a0) 98°95 95°90 96°35 0°26 —- 00 99°30 96°10 96°60 0°33 1°25 60 99°70 96°39 96°95 0°42 1227 65 100°20 96°65 | 97°40 0-52 1°24 70 100°80 97°05 97°95 0°68 1°30 75 101°60 97°60 98°68 0°82 1°30 SO 102°50 98°30 - 99°50 Peas | 1°35 8d 103°75 99°38 100°60 1°52 1°34 90 105°25 100°80 102-20 — ae Mean=1:28 | CHAPTER X WOOD PULP AND THE TEXTILE INDUSTRIES Tue celluloses and compound celluloses are produced in definite and characteristic structural forms, and only in such form. By chemical processes such as described in Chapter IL., we may convert the original structural celluloses into its amorphous or structureless forms by way of solutions of derivative compounds. It is clear, however, that questions of form and dimensions underlie every technical problem involved in the applications of cellulose. The following are the dimensions of the more important celluloses, considered as ultimate fibres. Length of Fibre. Diameter. Cotton 20—40 mm. — ine x Flax 25—30 ,, 0:015—0-037 ‘ine textiles. Rhea 60—200 ,, 0:030—0-070 rian 15—25 ,, 0:016—0-050 Jute 15—4:0 ,,_ 0°020—0-028 Coarse textiles Sisal 1:5—6°0 ,, 0°015—0:026 and Rope-making. }) Phormium o'0—18°0 ,, 0°010—0-°020 Breecad (Tracheids) 1:°0—20°0 ,, 0°015—0-020 Paper-making Esparto 05—3:0 ,, 0°010—0-018 It is somewhat remarkable that the most important cellulose, cotton, occurs and is industrially worked as an ultimate fibre or structural unit. Incidentally, it is worthy of mention that cotton is a seed hair, and in physiological function therefore, being con- cerned with a usually perishable tissue, it is not a priori 216 WOOD PULP AND ITS USES associated with permanence. On the same grounds and for the contrary reason we should expect to find in the wood substances which have long continuing or perennial functions, a chemical constitution implying superior stability. The paradox, however, holds that cotton is our type of chemically balanced cellulose and of a higher order of stability than the wood celluloses. To complete this point we must refer the reader to the previous section, which deals with the conditions of per- manence of the ligno-celluloses which are natural compound forms. We have to remember also that a wood cellulose is a residue always of chemical processes. As regards structure the woods are highly complex, whereas most of the textile fibres mentioned above are either bast fibres (bundles) or fibre vascular bundles. In the former case, as in flax, rhea, and hemp, the bundle is simple. It is more complex in the case of jute (see Chap. I.), and still more complex in the fibre vascular bundles of monocotyledons. Ksparto is a heterogeneous aggregate as in the case of the woods. In the mcre complex structures the celluloses are associated with various chemical groups (compound cellu- loses), which are attacked and removed by the various treat- ments of hydrolysis and oxidation by which the celluloses are isolated. For our present purpose we are concerned only with the celluloses in the form of ultimate fibres. These are the unit elements of structure of the yarns and threads which are the basis of textile fabrics. The mechanical properties of these, as well as the processes by which they are mechanically prepared and ultimately spun, WOOD PULP AND THE TEXTILE INDUSTRIES 217 are obviously determined by their simpler elements of form— that is, their dimensions. The mechanical principles involved in the production of fine textile yarns from these discontinuous units, are first, the reduction of these to a common untwisted. sliver, in which they are parallelised; secondly, the drawing and twisting of the fibres composing the sliver in continuous length. The tensile properties of the resulting yarn depend mainly upon the twist, partly upon the adhesion of the more or less closely-spun fibres. There are numerous variations of the process, such as the wet spinning applied to bast fibres and notably flax, the passage of the sliver through a bath of warm water facili- tating the ultimate subdivision of the bundles of fibres in the final drawing and twisting operation. In the coarser textiles, such as jute, it is evident that the spinning unit is an ageregate or bundle of the ultimate fibres, which are too short (2 to 8 mm.) to admit of manipulation. They are worked in lengths, which have reference to the conditions of the machinery, most convenient for preparing, drawing, and twisting. But it must be borne in mind as a fundamental technical fact that the ultimate properties of the yarn are conditioned primarily by the length of the ultimate fibre. This will be evident from the table (p. 282), giving the relative strengths of textile yarns in terms of actual tenacity and apparent elasticity (extensi- bility). We have added to the list the new products known as artificial silk, or lustracellulose. This being pre- pared from structureless solutions of cellulose derivatives may be considered as structureless. In this sense they 218 WOOD PULP AND ITs USES resemble the true silks which are produced in solution in the glands of the silkworm and extruded into the atmo- sphere, the worm performing the mechanical operation of drawing and laying the threads in the specialised form of cocoon. The structureless cellulose, in the form of a thread of regular dimension, presents to us a case of mechanical pro- perties of a substance independently of the grosser structural details which characterise the natural cellulose fibres, and it will be seen that cellulose admits of very severe treat- ment in passing through a cycle of operations and reverting to an amorphous substance which retains much of the structural properties of the original. Reverting now to the fibrous celluloses, there are certain features common to the paper-making and the textile industries. Thus, a web of paper and a textile yarn may be made from the same raw material, and, more- over, have the common characteristic of an agglomerate of discontinuous fibrous elements produced in continuous length. The strength or cohesion of the two fabrics depends in the first place upon the surface adhesion of the fibrous units, but in the case of the textile yarn this is a much less important factor than the “ twist’? communicated by the spinning process. On the other hand the paper web, though devoid of twist, presents certain characteristics in the opposition and adhesion of its structural units, which makes it a more coherent agglomerate than the yarn. Generally this is referable to the wet processes of the paper-maker, which brings the colloidal fibre substance into a condition of hydration or gelatinisation, in which a more intimate adhesive contact of the fibre surfaces is determined. ‘he © WOOD PULP AND THE TEXTILE INDUSTRIES) 219 cohesion is augmented by the pressure to which the web is subjected while still in the wet state and the union of the fibre surfaces is finally cemented by the drying or dehydra- tion of the web. Conversely, when re-wetted a paper is brought -back into approximately the condition of the web as first put together and its cohesion in this state or wet-strength, is only a fraction of that of the paper. | The cohesion of a textile yarn, on the other hand, is only slightly affected by wetting, and the effect indeed is not necessarily in the direction of diminishing tensile strength. . | The main point of contrast between these great divisions of manufactures devoted to the industrial utilisation of the vegetable fibres, is the length of the unit fibre, or fraction of fibre, in the final state of preparation of the raw fibrous material. Generally, we may say that the limit of economic handling in the textile industry is reached with a length of fibre of 83—5 mm. This inferior limit expresses, on the other hand, the outside limit imposed upon the paper- maker for the satisfactory working of his wet web upon the wire cloth of the machine or hand mould, and for the majority of papers a length of 1—2 mm. is a working optimum. This corresponds with an obvious complementary rela- tionship of the two industries, and the paper-maker, up to fifty years ago, was practically limited, as to raw material, to the wastes of the textile industries. In later times there have been notable advances in the method of working up short fibre wastes by the spinner’s dry methods, “‘ ginning process,” and, by special modifica- tions of teasing or carding machines, the utilisation of 220 WOOD PULP AND ITS USES these short fibres has been carried to extreme limits. As a question of cost of production it is found, however, that the paper-making process has considerable advantage. The problem then arises of converting the continuous length of paper into a textile yarn, with the associated question of the actual utility of the product. The elements of the problem are these :— (1) The subdivision of the web of paper into strips of suitable dimensions. | (2) The rolling of these strips continuously into the cylindrical form. | (3) Subjecting the cylindrical length of paper “ felt” to a twisting operation so as to increase its tensile strength to a Maximum. Having by these processes appreciated to a maximum the tensile qualities of the fibrous agglomerate, we still have to reckon with the intrinsic limitations of quality, due to shortness of fibre, on the one hand, and the fact that when wetted the product loses its cohesion. This is a general and somewhat “ theoretical’’ exposé of the technical basis of an industrial movement which has been in progress since 1891, toward the utilisation of paper in the form of a textile. It may be noted that this move- ment, though quite new to Europe, is based upon old- world practice, for the Japanese have for centuries used paper as a basis of string or twine, twisting paper strips of convenient width into the cylindrical form, and also piecing successive lengths to produce a virtually continuous fabric. This, however, was a manual operation performed upon the finished paper, and the product is only crudely suggestive of the pulp yarns which have been evolved through various WOOD PULP AND THE TEXTILE INDUSTRIES 221 stages of perfection by the work of EKuropean inventors bringing to bear upon the problem the resources of modern mechanical appliances. The development of this industry is mainly due to the enterprise of a succession of German inventors, and an excellent account of their labours is contained in the treatise of Prof. E. Pfuhl, ‘‘Papierstoffgarne (Zellstoffgarne, Xylolin, Silvalin, Miella) ihre Herstellung, Higenschaften und Verwendbarkeit,’ published by G. Hoffler, Riga, 1904. This treatise on ‘ Paper-pulp-yarns, their pre- paration, properties and applications,” is a very complete technological account of the matter, to which the specialist student must refer. In the general account which follows we have made free use of the matter of the treatise, and we acknowledge our indebtedness to the author and publisher. It appears that the evolution of the industry is set forth in the subjoined outline of inventions, as embodied in German patents. Practical success is claimed to have been achieved by three of these systems, each of which represents a consolidation of two or more patented inventions :— (a) The system of Claviez & Co. is based upon a finished but unsized paper as raw material. This is cut into fine strips, of a few mm.’s width, each strip being separately wound on a bobbin, which is then transferred to a spinning or twisting frame. In the form of twist it is subject to a rolling process to consolidate the thread, and this treat- ment is repeated, after moistening the thread, in a second machine, the speed of which is adjusted to produce a certain drawing effect. The spindle designed by Claviez for the spinning or 222 WOOD PULP AND ITS USES twisting of the paper strips is represented by the accom- panying figure (Fig. 24), the spool or reel carrying the paper strip of 2—3 mm. width is carried on the hollow brass axis b, which is held in position on the spindle s by means of springs. The fliers f rotate in the same direction in which the paper strip was wound on the spool; the strip is thus twisted and drawn off through rollers under suitable tension. The yarns pro- duced under this system are known as ‘‘ Xylolin,”’ and they are stated to have firmly established themselves in the textile industry, competing chiefly with jute yarns. A considerable refinement in pro- duction has been aimed at in the two sroups of inventions about to be Peed nmdlon ter described, for which the starting twisting paper-strips. point is not a finished paper, but the _@ carries the con- wel in the unfinished condition in tinuous length of paper i ay : of 2—3 mm. width: which it 1s delivered from the press EEO CS rolls of the paper machine. erat Scie nis (b) The Kellner-Turk system is the consolidated result of the inventive work of the late Carl Kellner, of Hallein—a well-known pioneer of the wood pulp industry—and of G. Turk, of Bad Gastein. The main patents are those of 1891 (D. R. P.-78601) and 1892. (. R.. P.. 79272) “andthe claims are similar, the former indicating the formation of a pulp-sliver by taking moist paper strips as delivered from a cylinder paper machine, and subjecting them whilst still WOOD PULP AND THE TEXTILE INDUSTRIES = 223 on the cylinder wire to a rubbing and rolling treatment by which they are rounded and consolidated; the latter patent indicates the same general plan of manufacture, but the rolling of the strips takes place after they have left the machine wire. ‘The production of the paper or pulp strips is not patented. ‘This 1s effected by the special construction of the wire cloth of the paper-making cylinder, which is an alteration of impervious brass strips with the ordinary 60— 70-inch mesh wire cloth; the pulp is deposited on the latter only. These patents were acquired in 1900 by the Patentspinnerei A.G., in Altdamm, Stettin, in whose hands the process was further developed in the direction of the Turk patent. The main feature of the treatment of the strips is the process of conversion from the flat to the cylindrical form, under which there is an incidental consolidation of the fibrous aggregate. This effect is produced by passing the strips through a special apparatus, the principle of which may be traced to an invention of O. Schimmel & Co., Chemnitz, described in the German patent 76126, above cited. ‘The invention was in its inception applied to the ‘“‘lap’’ of dry-carded short fibre as delivered from a textile carding machine. The lap delivered at the full breadth of the card is received between a pair of rollers which divide it by a peripheral cutting arrangement into narrow strips, which pass forward to the rolling apparatus. This consists of an upper and under endless band of leather in close contact, disposed for motion in the horizontal plane, each round a pair of rollers moving in geared connection. The rotation of these rollers carries forward the now divided strips, but an alternating movement in the direction at ’ 224 WOOD PULP AND ITS USES right angles is communicated to the leather bands by eccentrics, and this movement is in turn communicated to the strips as they travel forward, under which they are continuously rubbed and rolled into cylindrical form. They ©. 6. © Gy. 1 ‘4 1 4 | | A I ; A ” P \ i / a | ! Z Ha ! ag ! : a a 1 1 ‘4, Po gg ed 1 1 da 1 if 4 ! | fe) @)~ ~ 1 | a \ 1 | | ene # La) ras Be | H . sie Rod wl} i eae ( y ee ED i Sey ia Cigaae} : eae E Sa SS — Re SScem Aa = as eae eee ae Q Ze <2 os ee Sed EE Spee nae Sees) ea=2 = Fy ia ee pees bitsoe | Skt pS atsv) acd 4, Un i, ) Nil Ecc asd Bs | Oak ies || ZZ Hi Ws 1 oe OH iS ZZ . = _ = =a Fic. 25.—Machine for rolling flat strips of prepared short fibre (sliver). The ‘lap’ is taken from the card P, sub-divided into strips in passing R R, rolled at N N, and delivered into cylin- drical boxes or cans, TT. (O. Schimmel, D. R. P. 76126.) are then suitably laid down in receivers, to be transported to the spinning or twisting frames (see Fig. 25). On the Kellner-Turk system, as applied to the wet pulp strips, a similar apparatus and process succeeds the press- rolls of the paper machine. ‘The endless bands of the rubbing and condensing rollers are in this case made of indiarubber. WOOD PULP AND THE TEXTILE INDUSTRIES) 225 The third operation, that of spinning or twisting, is carried out on the still moist thread. There are various devices employed in the textile industry for conferring the high degree of twist which characterises the textile yarns in their final forms; the same principles and forms of machine are pressed into the service of the paper-pulp- spinner. The twisting is mostly carried out on “ Ringzwirn- maschinen,” ring-spindle machines, i.e., frames carrying 60—70 spindles on the side. In making weft yarns, the delivery of the spun yarn is varied so that it may be wound directly into cops, or on to tubes placed over the spindles. There are two limitations to the efficiency of this system; one is in the mode of making the pulp strips on a cylinder machine. The alternative process and machine, based on the flat-running Fourdrinier wire, with its much higher productive efficiency, is adopted by them as the basis of the competing system which we shall next describe. The contrast of these two methods of converting beaten pulp into paper is well set forth in C. Hofman’s Handbuch der Papierfabrikation, ed. 1897, page 858. The second limitation of efficiency—that is, in output and therefore economic production—is in the speed of the machine and process of rounding and consolidating the strips. Taking 12—15 m. per minute as the speed of running, a machine of 80 spindles will produce in length from, 12° 80°x< 60 x 24 — 1,382°400' m: to 15 ‘x 80 x 60 X 24 = 1,728,000 m. per diem: these lengths represent 460 to 576 kilos. of a No. 3 yarn, or 115 to 144 kg. of a No. 12 yarn. In actual working, allowance has to be made for unavoidable breaks and stoppages, and the output is - taken at 30 per cent. less than these figures. It may be noted W.P. Q 226 WOOD PULP AND ITS USES that a beating engine (Hollander) of 160 to 200 keg. capacity (dry pulp), dealing with four charges in the twenty- four hours, would feed two of such special machines. In summing up his notice of this system, Prof. Pfuhl expresses himself as follows (page 33) :—‘“‘It is probable that a number of circumstances, in addition to the not very satisfactory output of the sliver machine, have contributed to the present position (end of 1906) of the system, which is that after many years of existence, as indicated by the dates of the patents, 1f remains without industrial extension.” In connection with the development of the Kellner-Turk process, a number of patents have been taken by Leinweber, which have been acquired by the Altdamm Company. These inventions have reference to details which are found to be essential factors of economic production, such as the sub- division of the web of pulp into small strips (D.R.P. 140011). The mode of distributing these to the further operations (140,666) a further patent (140012) has reference to the rounding of the strips to a sliver by causing them to pass through a funnel, the tube of which is of spiral or other special construction, this treatment immediately preceding the spinning or twisting. System of R. Kron. ‘‘ Silvalin” yarns. It will have been evident during this discussion that wood-pulp ‘‘ spinning” is a hybrid process: a cross adapta- tion of well-known paper making and textile methods to the production of a particular type of fabric, and involving in a very special sense the question of cost of production. It may be noted in illustration of this point that while papers and staple textiles are produced and sold under a very wide range of costs and prices, the new industry in WOOD PULP AND THE TEXTILE INDUSTRIES 227 the hybrid products depends mainly upon cost of production. The system which consolidates the inventions of Messrs. Kron claims important progress in this essential element of success. In the first place, the production of the original pulp-strips is “‘intensified” by employing the ordinary Fourdrinier machine at its full width, the web being sub- divided into narrow strips by an arrangement for projecting jets of water upon the web at such distances that the web is divided into 100—500 strips per metre. The separation of the strips is, however, not thus completed; they are wound up on a roll of the full width, and are afterwards separated and detached as discs. It is based upon the following patents, of which the subject-matter indicates the essence of the several inventions :— | I. Main patent (K. 23200 vii/76c). A process for twisting or spinning the cellulose (pulp) directly from pulp-rolls. (a) Addition-patent I. (KX. 23887 vii/76c) for winding up the wet-web at the breadth of the machine to be after- wards divided in pulp-dises of suitable narrow width, (b) Addition-patent II. (K. 23926, vii/76c). Improve- ments in the manufacture of pulp-rolls in a moist but coherent state. II. Main patent (K. 25168, vii/76c). Process and apparatus for winding up moist strips of paper pulp, etc. III. Main patent (K. 25043). Process and apparatus for sub-dividing a web of pulp (as on the wet end of a paper machine) into strips. IV. Main patent (K. 26001). Apparatus for direct delivery of moist pulp strips. V. Main patent (K. 25036). Spinning machine for preparation of detachable cops. Q 2 228 WOOD PULP AND ITS USES The succession of operations in the Kron system is as follows :— 1. The formation of the web on the Fourdrinier wire ; its sub-division into strips by the impact of jets of water for the number of strips required to be formed. 2. The pulp-strips are subjected to the action of press- rolls for the gradual removal of water and progressive solidification of the fibrous aggregate; it is then further dried by heat on a steam-heated cylinder ; and then wound up in what is termed a magazine roll, which thus holds a series of discs in close contact. These are detached as required for the further operation of twisting, and are disposed for winding off in a horizontal or inclined position beneath the spindles. | 8. The winding off and twisting involves the passage through the machine which is the subject-matter of patent No. 4 (ante) from which the strips are delivered continuously to the spindles. These have a speed of 3,000 to 8,000 revolutions per minute, with the sliver travelling at 8 to 16 metres per minute, according to the size of the yer and the degree of twist required. The following table of results of tests of tenacity and ‘elasticity’ more particularly illustrates the technical features of the wood-pulp “‘ spinning” systems :— Metrical count. Breaking strain Extensibility in terms of per cent. breaking length. Silvalin strips (dry) 2,891 2,390 3°06 satay ars. : 2,900 4,810 6°44 Altdamm (Tiirk) aes . 18,158 4,170 2°84 Strips rounded (sliver) . 8,222 5,014 2°24 4 : 8,408 5,187 Phas Finished yan . . 12,100 6,413 3-06 WOOD PULP AND THE TEXTILE INDUSTRIES) 229 From his extended investigations of these products Prof. Pfuhl concludes that this class of yarns made from pure wood-cellulose have a mean breaking length of 5 to 7 km. with an extensibility of 6 to 7 per cent.; and these constants define a textile quality sufficiently high for their utilisation under the ordinary conditions of wearing, both as warp and weft. The warps of wood-pulp yarns require no previous “dressing” or sizing. The finished fabrics, it may be mentioned, have about one-half the strength of jute fabrics of the same make and weight. In regard to the conditions of utilisation of such fabrics, it is to be noted that, when wetted, they lose their tensile quality entirely ; and although they regain their strength in drying, it is evident that the defect in question is a serious limitation of their utility. (b) Cost of Production of Silvalin Yarns.—The estimates of Prof. Pfuhl are based upon a daily output of 6,000 kg. or 1,800 tons per annum, involving 2,160 spindles running eleven hours; the corresponding production of sliver-strips running continuously, 2.e., twenty to twenty-four hours per day. In the estimates, the production of a No. 3 (metrical) yarn is considered. The capital outlay is summarised as follows :— Marks. Site and land, 15,000 kr.... es Lo SSI Buildings, 2,000 mr., ete. a Aud LOO Machinery and plant... OF ... 809,500 Business capital ... ee ie ... 126,800 523,000 These represent an annual charge of about 36,000 m. and adding salaries the establishment represents a charge of 230 WOOD PULP AND ITS USES 56,807 m. per annum. Wages are estimated at 60,320 m., and coal (at 20 m.) 48,160, adding for lighting, packing, etc., 41,000 m. The total annual charge is 201,287 m. This on the basis above set forth gives a cost of production per ton of 111°88 marks. Adding 20 marks for one patent licence, we have a total cost of 181°83 marks. Comparing these costs with those of spinning jute to yarn of the same count, which was estimated at 100 to 120 m. under similar conditions, it is seen that they are some 10 to 20 per cent. higher. The respective raw materials have now to be brought into account, viz., sulphite cellulose at 15 to 18 m. per 100 kg., and jute at £10 to £14 perton. The final comparison is made in the following terms :— | Marks for 100 kilos. Jute warp yarn, No. 6... 34 43 Jute weft yarn, No. 5, 4 31 39 Silvalin yarn, No.5, 5... 28 32 Total cost of production Physical Properties and Application of Wood-pulp Yarns and Fabrics.—It has already been indicated, and is, in fact, more or less self-evident that wood-pulp yarns are limited in their utility. In measuring the utility a number of general principles have to be taken into account as well as the practices and conventions of the textile industry which follow fromthem. The numerical basis of measurement or weight length in the textile industry takes a number of conventional forms. The trade in coarse yarns which alone come into considera- the ‘counts of yarn” is the relationship, which tion here, is mainly concerned with flax, hemp and jute or bast fibre yarns, and low grades of cottons. Thus we have WOOD PULP AND THE TEXTILE INDUSTRIES 231 the English units or yarn numbers for bast fibre yarns = the number of leas (of 800 yards) in the pound; for cottons the number of hanks (of 840 yards) in the pound. The jute trade (Dundee) takes an inverse measure in terms of the “‘ spindle” of 14,400 yards, the number of pounds in this length being the yarn number. For wood-pulp yarns the simpler metrical numeration obtains, viz., the number of metres (unit of length) to the gram (unit of weight). The following table, of the metrical yarn numbers and their equivalent in the conventional units will be found useful. Table of equivalent yarn ‘‘ numbers” or WEIRD length description compared with metrical counts. Metrical counts: Cottoncount: Flax counts: Jute counts : metres per n. (840) yds. n. (300) yds. lbs. per 1 grm. per lb. per lb. 14,400 yds. 1°0 et UO: O0 Lares. 1G 545i ee cs ee ORO GU oiete. 1°0 Hee 2BOO Mw @.. tee Lie O:O05ees.. OOS (anaes 1:0 tee to 29°0 cee CA ee 450) mt 1°0 The strength or “tenacity” of yarns is determined as a breaking-strain, but usually expressed as a breaking-length, that is, the length of the breaking-weight of the yarn itself. This is comparable at once with the sectional breaking- strain usually applied to solid substances. For where L expresses breaking-length, s specific gravity, and k the breaking-strain per 1 mm. of sectional area, LZ X s = k. Breaking-Length.—lt is an expression which eliminates two of the three dimensions, that is, it is independent of the sizes of yarns or threads, as of the thickness or width 232 WOOD PULP AND ITS USES of fabrics such as paper produced in sheet or web. It will be noted as a conventional expression, but of very great “convenience,” and gives a comprehensive or aggregate expression of tensile quality, and thus is applicable to the most diverse substances and in their most varied form. Fracture of a textile yarn or paper is accompanied always by elongation under the strain; this of course is a certain measure of true elasticity. The latter would be defined as the amount of .extension of which the fabric is capable, with the condition of reverting to its former dimen- sions when the strain is removed. This quality, however, - is seldom defined or tested in textile fabrics. Extensibility is usually expressed as the total percentage elongation sustained at or under the breaking-strain. The following table of these quantities applies to the most important textiles. Breaking Length. Kilometres. Elasticity. ¢ Cotton yarns a .. 13—14 3°97 Ramie yarns - .. 11—12 0-S—1°'8 Flax yarns, wet spinning.. 12°4—19°5 1:1—1°8 Mean averages for ean averag Flax and tow yarns, dry Commercial eas 2 spinning .. a .. 11:8—12°4 2°5—3°7 Products. Jute yarns + = e ao 2°0 Lustra cellulose average .. 12:0 2°0 Artificial silks, extremes.. 8°0—14:0 7:0—18°0 The mechanical properties of papers are expressed in the same terms, and it is interesting to compare the range of numbers for the highest classes of papers :— Breaking Length. Elongation. Metres. Per cent. Rag papers, Manila papers and wood pulp papers (air dry) ... 4,000—8,000 ... 3°8 It is evident from these numbers that the shorter units WOOD PULP AND THE TEXTILE INDUSTRIES 233 common to papers produce a texture approximating in mechanical properties to the lower grades of spun yarn. From the preceding exposé it would appear that inventors have endeavoured to overcome the unfitness of paper as such for textiles, or weaving uses, by changing the form and usual dimensions of the web of paper. The stages in the productions of a cylindrical product or yarn are (1) cutting, (2) rolling and (8) subjecting the cylindrical rolled strips to a twisting process whilst in a moist condition. The effects of these treatments in increasing the solidity and resistance of the agglomerates is shown by the following figures :— Breaking cee Elongation. km Per cent. Plane strips, dried emi ee el: 4: 17 ge Mee Rolled into cylindrical form... DLO see wee Rolled and twisted os Be 641 ... 3°06 The following numbers have reference to wood-pulp yarns as industrially prepared : Silvalin (Kron process, 1908—4) : Menneome24 0 toctsme rn) ea 5498. "Gis Maximum observed oe e S50 4a LOD Minimum observed ae *. AS1 Oar ee 9 Altdamm (Turk process, 1903—4) : Mean of 90 tests a i. IGE aes Ayal Maximum observed ee ae TEE Bs etna LEG Minimum observed ne cr O,ULO ee eee As a chemical individual wood cellulose differs but little from cotton cellulose ; and when only chemical relationships are involved, there is an obvious probability of the former being able to substitute cotton as a basis of manufacture. 1 Km. is the contraction for kilometre. 234 WOOD PULP AND ITS USES For such substitution there is always the inducement of relatively low market price. SPECIAL CELLULOSE INDUSTRIES. There are several important industries which have been developed upon the characteristic properties of derivatives of cotton cellulose. The modern industry of high explosives is based upon the nitric esters of cotton, which in certain cases are associated with the corresponding nitrates of glycerine. As shown in Chapter II. cotton can be nitrated, that is, combined with nitric acid by simple methods and without any evident structural change. The nitro-cotton, or gun cotton, has the external appearance .of ordinary cotton, but is harsher to the touch, and the addition of the large weight of 70 or 80 per cent. due to the combination with nitrate groups, causes minor structural changes which can be well observed under the microscope. The properties of gun cotton are primarily those associated with rapid or explosive combustion ; combination with the nitric groups introduces so much oxygen into the molecule that the new compound has all the elements or internal conditions for complete combustion, whereas ordinary combustion depends upon the gradual supply from without of atmospheric oxygen to the burning body. When eun cotton is fired, there is a rapid propagation of the. combustion, and when this takes place in an enclosed space detonation occurs, with rupture of any containing vessel, due to the enormous development of gas’ at high temperature. 1 The products of explosion of the nitrate are represented by the equation 2 Co4H 3.05 (NO3H)i = 24°CG0 + 24 CO, + ity H, + 12 H,O + 11 N, and the heat evolved is 2,200 calories per 1 gramme. WOOD PULP AND THE TEXTILE INDUSTRIES 238 The cotton nitrates are soluble in a number of organic liquids in which they swell up and pass into homogeneous solution ; with limited proportion of such solvents, and mechanical means, the fibrous nitrates may be worked up into structureless plastic masses, which can be drawn or moulded into threads or rods, or rolled into sheet. It is an important discovery that glycerine or nitro-glycerine is a solvent of nitro-cellulose. Nitro-glycerine resembles nitro- cotton in fundamental combustibility, and is similarly a high or blasting explosive, even more powerful than nitro- cotton, owing to the somewhat higher relative proportion of oxygen. It sounds like a paradox that on bringing these two high explosives together a mixture results which has the properties of restrained combustion, or regulated explosion. These bodies worked together in suitable proportions pro- duce a plastic mass which can be drawn, as above stated, or shaped. When flame is communicated, there is a regulated combustion proceeding from the external layers to the * centre of the mass. Explosives of this order can, in fact, be used as propulsive explosives, that is for military ammunition; the ordinary forms are cordite, balistite, etc. It would appear to be possible to replace cotton for the manufacture of nitro-cotton by, the wood celluloses, but there are many reasons, partly of constitution, and partly having to do with the external characteristics or fibrous forms, which have prevented this from taking any deep root, and we can therefore hardly enter into the specialised technology of gun cotton and explosives as a development of wood-pulp industry. The same may also be said of the very important industry in articles known as celluloid, xylonite, etc. ‘This 236 WOOD PULP AND ITS USES art and industry is based upon the plastic qualities of nitro cellulose when treated with suitable solvents, and ~ the plastic mass obtained by incorporating the fibrous nitrates with special solvents and completing the mixture to a homogeneous mass by means of mechanical appliances, can be shaped into any required form. There are particular reasons why this industry also has not availed itself of the supplies of wood cellulose of which the market value is approximately one-third that of the forms-.of cotton which are ordinarily used. These reasons, as previously indicated, are partly in the. relative inconvenience of handling the short fibres of the wood celluloses: and partly from the particular features of instability characterising compounds which are potentially self-destructive. Gun cottons and the lower nitrates of cotton are “unstable”? as originally produced owing to the presence of sulphuric acid residues in combination. These are eliminated by exhaustive washings and successive boilings with water. When so purified and “sterilised” they may be kept for prolonged periods without change. But other celluloses are constitutionally differentiated from the normal cotton cellulose, and contain a proportion of groups of less intrinsic stability: these nitrated to the same degree are correspondingly less stable, and liable to spontaneous decomposition. Hence a lower stability of the entire complex and unsuitability for these industrial uses. | Cellulose Acetates.—The highly combustible and explosive nature of the cellulose nitrates imports a considerable danger in the manufacture and use of celluloid or xylonite. An important use of the nitrates is for the manufacture of WOOD PULP AND THE TEXTILE INDUSTRIES) 237 photographic films, and in ordinary use this has not led to any serious catastrophe. On the other hand, the film employed to carry the photographic picture in the kine- matograph, the picture being projected on to a screen by means of powerful illuminants, is a combination of risks, which has led to several disasters. It is a well-known objective of inventors to discover an efficient substitute for the nitrate. Cellulose acetate is an ester of cellulose which is a close analogue of the nitrate, is also soluble in organic solvents, and may be shaped in admixture with these in any desired way. The first serious attempts to prepare the cellulose acetate on the industrial scale date from 1890. It was found by ourselves that certain forms of cellulose can be brought into reaction with acetylating reagents in presence of zine acetate, and such process was carried out on an industrial scale. Further investigations of other chemists led to the observation that cellulose combines readily with acetic anhydride in presence of sulphuric acid relatively in small quantity, and taking part only in determining the main reaction. Such a process, the subject of a series of patents by Lederer (see p. 240), has led to considerable economy in the production of the acetate, and the matter is being industrially developed in one or two countries. The acetate film answering all the requirements of photographic use is still, however, in the embryo stage of development. Owing to the simplicity of the reaction and the relative inertness of acetyl groups, there is every reason why the wood celluloses should answer all requirements for this industry. The reaction is usually carried out with a mixture of glacial acetic acid and acetic anhydride in equal 238 WOOD*PULP AND Ips sins proportions to which the calculated small quantity of sulphuric acid is added (Lederer); in contact with this reactive mixture, the celluloses are gradually and pro- eressively attacked and pass into solution: Low tempera- tures only are required, and 50°C. is the general maximum. The product is obtained asa highly viscous liquid, that is, a solution of the ester in the excess of the reactive mixture. The mixture is treated with water, which precipitates the ester, and, by suitable mechanical means, this is effected in a state of minute subdivision of the ester, so that it is easily washed. When dry it dissolves to bright solutions in its special solvents, which are chloroform, ethylene chlorides, acetic acid, phenol, etc. It is to be noted that these solvents present difficulties in use, and they are by no means so convenient as the solvents used for the nitrates. Variations of the process, however, have led to the pro- duction of acetates soluble in acetone, a solvent which is free from objection in use. An important question of cost necessarily enters as determining the extent of application of these bodies. Owing to the relative high price of acetic anhydride, and the necessity of using an excess of reaction mixture, the costs of acetate obtained as above. described is relatively high. In employing solvents, which are lost in the working of the acetate to particular forms, the cost is added to. Whereas cellulose nitrates can be bought in the open market at from 1s. to 2s. per lb., the acetates stand at a multiple of these figures, viz., 6s. to 9s. a lb. It is evident that such prices exclude applications save such as are relatively independent of cost. Another point to be noted in connection with these WOOD PULP AND THE TEXTILE INDUSTRIES 239 acetates is that while the reaction is direct, and, in one sense, simple, there is no doubt that the use of acid catalysts brings about the breaking down of the cellulose ageregate by hydrolytic change, from which results a loss of structural properties. The acetates so produced and converted into continuous solids are relatively brittle. Processes which overcome these objections depend upon the use of neutral or saline catalysts, such as zine chloride. These appear to determine the ester reaction under con- ditions which do not involve hydrolysis or, at least, involve it to a much less extent. The products of such reactions are what may be considered the normal series of acetates. The reaction of cellulose with acetic anhydride in the presence of zinc chloride as catalyst, and glacial acetic acid as diluent can be observed through a remarkable series of eradations up to the extreme or maximum point. If cotton is used, or more particularly cotton yarn, it is easily seen that the lower acetates are formed without any sensible modification of the cellulose or yarn. Acetyl groups may be introduced into the cellulose molecule with an increase of weight up to 26 to 86 per cent., producing an acetylated derivative unchanged as to form, showing certain new properties in respect of lower attraction for atmospheric moisture, and for those colouring matters which dye cotton directly. When carried to higher stages, the further intro- duction of acetyl groups cause a notable swelling of the cellulose, and, finally, as the stage of tri-acetate is reached, the product passes into solution. This method of acetyla- tion is economical by reason of the fact that there is a very high utilisation of the acetic anhydride. A further point of economy arises in the application of 240 WOOD PULP AND ITS USES the acetate, since for certain purposes the reaction mixture itself can be employed. This avoids the process of separa- tion of the ester, in which the solvent is lost, or so diluted as to have a much depreciated value; and, moreover, the separated ester requires again to be treated with solvents, which become an added cost. These difficulties, which appear of small magnitude, have effectually impeded the development of the applications of the product. A general bibliography on the subject since 1895 will indicate the directions in which specialists may inquire for evidence of the influence of these difficulties on the evolution of this cellulose ester. GENERAL BIBLIOGRAPHY OF CELLULOSE ACETATES. Original papers. Schutzenberger and Waudin. Comptes Rendus, 68, 814. Franchimont. Berl. Ber. 12, 2059. Cross and Bevan. Journ. Chem. Soc. (1890), 57, 1. 1905 Cross, Bevan and Briggs. Berl. Ber., 38, 1859, 3531. Haeussermann. Chem. Ztg., 29, 667. 1906 Ost. Zeitsch. Angew. Chem., 19, 993. 1907 Berl. and Watson Smith. Berl. Ber., 40, 903. L003 aes a Journ. Soc. Chem. Ind., 534. F. Beltzer. Mer. Sci., 22, 648. Knoevenagel. Chem. Zeit., 32, 810. 1895-1905 Cross and Bevan. “* Cellulose.” “¢ Researches on Cellulose,” I., ‘‘ Researches on Cellulose,” II. The following patents. 1894 Cross and Bevan. 1900 Lederer. . 96761. ~ 11749. Ct et bt be ih Ost toed 1902 Landsberg. . 4886. », Lederer. . 7088. } eesti. . P. 708457. WOOD PULP AND THE TEXTILE INDUSTRIES 241 Miles. Farbenf. Elberfeld. Balston and Briggs. F. Rayer & Co. Lederer. Badische, A. 8. F. Miles. Fabr. Prod. Chim. Flora. Akt. Ges. f. Anilin. Farbenf. Elberfeld. Corti. Lederer. F. Bayer & Co. Knoll. Badische, A. 8. F. Lederer. Fischer. Knoll. Benne. Soc. Anon. Explosifs. Lederer. Knoll. Donnersmarck, K. A. W. 9) Lederer. aq HAC HG OHO ROR eR dda ee Hat nett th PWN Etter t thon aomn P, 733729. P, 734123. P. 738533. 10243. 7346. Pan b40 bl . 347906. 19330. 9998. 1939; F. P. 362721, 368738. P. 809938. P. 816229. . 19107, 26502. . 368766, 371357. 371447. 369123. . P. 373994, 812098. 3108. 374370. ee 290 . 2026, 2026A, 2026B. . 373994. . 383636. . P. 210519. . 385179. ts 9020933 p dey tse N Og ey 7743. . P. 922340. . 400682. ES 11625, The derivatives above described are themselves esters or compounds of cellulose and acid groups, and are treated or manipulated as such. Thus, the solutions of both the nitrate and acetate can be drawn or spun to a thread, which, when sufficiently fine, is an artificial silk. The nitrate is the basis of the earliest, and still very successful, W.P. R 242 WOOD PULP AND ITS USES method of producing these artificial textiles, nitro-cellulose is only a stage in a cycle of industrial operations. The nitrate is readily denitrated, that is, its nitro groups may be removed with regeneration of cellulose. The earlier forms of artificial silks were not so treated, or, at least, only partially denitrated, and therefore were necessarily highly combustible, if not explosive. This property very con- siderably prejudiced the earlier attempts at utilising them : this form has, however, given way to the denitrated or cellulose product, which is now an ordinary staple textile. The acetate in the form of thread or artificial silk could be used as such, as it is not more combustible than ordinary cotton. It is a product, however, that is still only an industrial curiosity, and has not taken any prominent position, probably owing to the cost of production of the original acetate which, for the reasons given, is necessarily high. A further difficulty in the same direction is the added cost of redissolving the products in solvents, which are lost during the spinning process. ‘There appears to be, however, a prospect of producing a thread to compete with the artificial silks already established, by spinning or draw- ing the original reaction mixture in the case of the normal series of acetates. We have already described a peculiar compound of cellu- lose, which resembles the above in being formed by com- bination of cellulose with acid groups; but the compound is soluble only in alkaline liquids, and, moreover, is” unstable, that is, decomposes spontaneously with reforma- tion of cellulose. This compound is the sulpho-carbonate, or xanthogenic ester of cellulose, generally known as ‘“‘Viscose.”” This compound was described briefly in an WOOD PULP AND THE TEXTILE INDUSTRIES 243 early chapter, and its capabilities of regeneration in struc- tural modifications were indicated. Viscose has been used in a number of industrial applications, all of which depend upon this essential property. (1) In thread or yarn, it is an artificial silk. (2) In plane or sheet form it is a transparent film. (8) Solidified in masses it is a solid, which, when dried, can be shaped or turned in the lathe to any required form. The cellulose can also be mixed with solid bodies in preparing mixed agglomerates in which the structural qualities of the cellulose as the binding or agelomerating medium assert themselves, even when diluted with large proportions of foreign inert matters. (4) In less definite forms, but exerting the same technical effects, viscose is used in sizing paper and textiles, and for various other applications. For the general reasons above stated these industries are not necessarily connected with wood pulps, since they are more generally applications of cellulose, As a matter of fact, however, the wood pulps are a most convenient form of cellulose for the manufacture of viscose, and we may therefore give a few particulars in elucidation of these newer developments. The first stage in the “‘ viscose process”’ is the conversion of the cellulose into alkali cellulose by treatment with caustic soda solution at mercerising strength (15°0O—20°0 per cent. NaOH). The limits of composition of this product are Per cent. Cellulose . sae! i : 25—30 Caustic soda (NaOH) : : 12°5—15. Water. : : ¢ : 62°5—55 R 2 244 WOOD PULP AND ITS USES There are two methods of treating the wood pulp (cellu- lose) with the alkaline lye. The first is to reduce the wood pulp in a kollergang with sufficient water to bring about the disintegration of the sheets, and then add the calculated quantity of caustic soda dissolved in such a quantity of water as to produce a mixture of the above composition. The second method is to steep the sheets in excess of a lye of 17°5 per cent. NaOH, lift, drain from the excess, press to a calculated weight, and then grind in a kollergang or mixer to secure even incorporation of the mercerising reagent with the cellulose. The alkali-cellulose is a voluminous semi-dry mass resembling bread-crumbs in appearance. It can be stored in masses without change of composition by drainage. The alkali-cellulose is protected during storage from access of atmospheric air—that is from the action of atmospheric carbonic acid. The second stage in the process is the reaction of the alkali-cellulose with carbon bisulphide. This takes place spontaneously at ordinary temperature. It is important to carry out the reaction in a closed vessel to prevent loss of the very volatile bisulphide. The vessel ordinarily used is of the form and construction of a churn. In dealing with large masses it is found of advantage to replace the simple barrel or cylinder by a vessel of hexagonal or octagonal form. The charge of alkali-cellulose having been intro- duced, the quantity of bisulphide is poured upon the mass, the vessel closed at the man-hole and slowly rotated, to secure even admixture and distribution of the contents. The reaction is attended with a rise of temperature of 3 to 7°C. according to the mass, initial temperature and other WOOD PULP AND THE TEXTILE INDUSTRIES) 245 conditions of reaction. The mass changes in colour to yellow, and the action is arrested at the moment that it begins to lose its voluminous free condition. The completed product tends to agglomerate, and for the purpose of making a solution it is important that this should be stirred into water before the stage of agglomeration is “reached. There are in fact two ways of working up the xanthate: the first is by the action of water to a solution of 10 to 12 per cent. cellulose strength, the second, the agglomeration is completed by the action of heavy masticating rollers, such as are used in the manipulation of indiarubber. The latter method is, however, only used in connection with the making of solids which are shaped into cylindrical form as a stage in the preparation of the solids known as viscoid or viscolith. The viscose solution is the starting point for the prepara- tion of artificial silk. For this industry the crude solution is subjected to filtration which requires to be of a very searching kind. In spinning or drawing the silk the solution has to pass through orifices of fine dimensions, 0°1 to 0°15 of a millimetre, and hence it is important to eliminate all residues of insoluble matter. The xanthate or soda salt of cellulose xanthogenic acid is the basis of viscose. It is accompanied by by-products of the original reaction and moreover, as it tends to spon- taneous decomposition by interaction of the alkali with the sulpho-carbonic residues in combination with the cellulose, there is an accumulation of these by-products at the expense of the xanthates, which hold a steadily diminishing pro- portion of the characteristic group. The spontaneously 246 WOOD PULP AND ITS USES diminishing ratio of these groups to the cellulose is attended by diminishing solubility of the cellulose complex. Further, the by-products are soda salts of the carbonic and sulpho-carbonic series, and are precipitants of: the cellulose compound. In both directions therefore there is a tendency for the viscose to revert to the solid state. A solidified viscose is a coagulated xanthate, and may be washed in water, and then redissolved in caustic soda solution. The final stage in the reversion is cellulose itself, which is reached only after prolonged periods at ordinary tempera- tures. These phenomena are made use of in several of the applications of viscose, as 1n the engine sizing of paper and the sizing and finishing of textiles. The decomposition is hastened by the interaction of the soda salts with salts of zinc or magnesia, and these are employed in the process of paper sizing. Another characteristic decomposition is that determined by salts of ammonia. Viscose in contact with sulphate of ammonia in solution interacts quantitatively; the soda is converted into sulphate and is replaced by ammonia (base) in both the by-products and the xanthate. These ammonia compounds are extremely unstable, and therefore there is a very rapid decomposition of the xanthate to cellulose (hydrate). ‘This reaction is the basis of one of the methods of spinning or drawing to artificial silk. Another method which also fulfils requirements of the spinning process, is that of treatment with acids, which bring about a still more rapid decomposition. Notwithstanding the rapidity of action the cellulose WOOD PULP AND THE TEXTILE INDUSTRIES 247 hydrate adapts itself perfectly, and shows the same con- tinuity of substance and resistant quality as in the case of the saline baths. In regard to mechanical methods, these are two, in principle and detail. 1. The solution is projected from a fine glass tube: each individual thread is thus formed apart, and a certain number of these are united into a compound thread by passing through a glass loop in the coagulating or decomposing bath. The compound thread with its 14 to 18 elements is manipulated in the untwisted state, in the first instance ; at a later stage, as a special operation, it receives the twist of 100 to 200 per metre. An ingenious method of combining these operations is the centrifugal spinning box of Stearn and Topham. This is a box of special construction rotating at a high rate of speed on a vertical axis. In this case the compound thread is directly produced in the coagulating bath by projecting the viscose through a plane cap or nozzle of platinum perforated with 14 to 18 holes. Each hole con- tributes a thread, and these are drawn forward in the coagulating bath as a compound thread, which ascends and is taken vertically up and down over a glass roller to fall into a funnel which communicates with the rotating box. The centrifugal motion has the effect of drawing the thread forward, twisting it, and laying it peripherally in the box as a hollow or annular cocoon, The hydrated thread in this “‘cake”’ form is removed from the box at intervals, re-wound into skeins and further manipulated for purification of the cellulose. The industrial applications of viscose necessarily involve 248 WOOD) PULP ANDAITS USkKs a multiplicity of detail both chemical and mechanical. Chemically, the product is difficult to handle by reason of its alkalinity and the large proportion of derivative sulphur containing groups which are characteristic of the product and by-products. When these are decomposed, the. products are sul- phuretted hydrogen and other odorous derivatives. When the decomposition takes place spontaneously, the alkaline reaction being maintained, the products are carbon bisulphide and traces of other sulphur derivatives. The mechanical difficulties of handling viscose are largely a question of materials, that is, of materials having the power of resisting the attack of the associated products whether in the original condition or under the condition of decomposition by the reagents above indicated. It would be outside the scope of this work to deal with these matters in detail. A large number of inventions dealing with these methods and details have grouped themselves around the original invention, which dates from 1892. These inventions and developments are so numerous that they form the subject of a monograph of 127 pages, with 88 pages additional, devoted to the patent literature. We give the title of this work in full: ‘‘ Die Viscose—ihre Herstellung, Higen- schaften, and Anwendung,” von Dr. B. M. Margosches in Brunn. Leipzig. LL. A. Klepzig. This monograph is extensive, and in fact complete, and it is therefore unnecessary to duplicate this contribution to technical literature. In the course of discussions in this and preceding sections, we have not dealt directly with the commercial aspects of WOOD PULP AND THE TEXTILE INDUSTRIES 249 the wood pulp industries nor with the subject of their money or selling values. These involve questions of minute detail, anda special aspect of these industries outside the scope of the present work. But we may deal in a very broad and general way with these values, as an illustration of an important principle of technology, that is, the appreciation of value of a raw material worked up by the agencies of chemical reagents, coal and steam, and manual labour, into a finished manufactured product. The German language, we may note in passing, provides the apt term ‘“‘ vered(e)lung”’ which means literally “ennobling,” for this process of adding value to raw materials and the special term connotes the general idea and aim of manufacturing industry. We have to borrow a Latin equivalent, and this suggests that the idea of ‘appreciation ” 1s somewhat of an exotic. However the associated ideas may be expressed and assimilated the facts are equally striking and interesting, and in the case of the cellulose industries they may be stated in the form of an ascending scale of related values as follows:— (a) 1 cubic metre of wood weighs 400—500 kilos. and is worth in the forest, say ANB (b) Used as fuel it has a “burning” value, say O 6 O (c) As mechanical wood pulp it is worth, say . O 7 (d) Treated by the bisulphite or alkali process it would yield 150 kilos. of pulp, say Se ES (e) Transformed into paper the pulp or cellulose is worth, say . : : : - ee SAR ANGS AS 250 WOOD PULP AND ITS USES (f) Transformed into wood pulp yarn, it is worth, say . 2 69a (g) Transformed into artificial “ilk or Iatre cellulose, it is worth, say+~ < » .) 9 See These figures cannot be stated more exactly, that is, represent actual selling values; but fractional variations would not affect the general scale of values which mounts in multiples from 1 to 50. Specialists are aware that these achievements in ‘“‘ veredlung’’ by no means exhaust the possibilities of cellulose technology and industry. 1 This interesting industrial record we owe to Dr. O. Witt and Max Miller. CHAPTER XI SPECIMEN PAGES—VARIOUS TYPES OF PAPER Turs chapter embodies specimen sheets of paper selected as types, with a description of their characteristics. The selection is designed to bring out the position of wood pulps, in their various forms, as staple paper-making raw material. In establishing this position there have been, of course, the two elements of competition: first, technical effect ; and second, cost. As a result of the competition, the wood pulps have largely displaced cotton, jute and esparto. The general result of their introduction has been to cheapen production, with no sensible lowering of general quality. It is unnecessary again to point out that ground wood or “mechanical” wood pulp has many undesirable character- istics, and, of course, it is rigidly excluded from papers for documents of permanent value. But even this “Cinderella’’ fibre has proved of great practical importance and utility, in enabling papers to be produced at a cost commensurate with the enormous demand for cheap publications. The careful comparison of these papers, with attention to the full specification of characteristics printed on each sheet, will enable the reader to draw his own conclusions as to the extent to which wood has vindicated its present position as of first-rate importance. BIBLIOGRAPHY TITLE AND AUTHOR. Beitrage zur Kenntnis der Che- mische zusammensetzung des Fichtenholzes. . P. Klason. Berlin, 1911: Borntraeger. Cellulose, 1895. Researches on Cellulose, I., 1901. Researches on Cellulose, IT., 1906. Cross & Bevan. Chemistry of Papermaking. Griffin & Little. New York, 1894: Lockwood. Die Chemie der Cellulose. G. Schwalbe. Borntraeger. Die Cellulose Fabrikation. Schubert. Berlin, 1906. Etudes sur les Fibres Végétales textiles. M. Vetillart. Paris, 1876. . Carl. Berlin, 1910: Max Introduction to Vegetable Phy- siology. J. Reynolds Green. 1900. Paper-maker’s Pocket Book. J. Beveridge. Papierprufung. Herzberg. 3rd edition. Berlin, 1906. Pflanzen Faser. Hugo Mueller. Reports Vienna Exhibition, 1873. CHARACTER OF SUBJECT-MATTER. Theoretical investigation of con- stitution of pine wood. Systematic account of the chem- istry of cellulose and deriva- tives, and special accounts of researches to date. Modern account of wood pulp processes. A compilation on various works on cellulose. A practical text-book dealing with wood pulp processes. A standard book of reference on vegetable fibres, dealing with minute structure and correla- tion of microscopic charac- teristics with industrial uses. A standard text-book of plant physiology. Tabulated constants and numeri- cal statistics incidental to manufacturers. Original investigations on vege- table fibres. 264 TITLE AND AUTHOR. Plant Structures. Coulter. New York, 1900. Praktischer Handbuch der Papier- fabrikation. Hoffman. Berlin, 1897. Technologie der Fabrikant. E. Kirchner. Biberach, 1905-7. The Paper Trade. A. D. Spicer. London, 1907. Die Viskose ihre Herstellung Eigenschaften und Anwen- dung. Leipsic, 1906. Mar- gosches. WOOD PULP AND ITS USES CHARACTER OF SUBJECT-MATTER. An excellent book, dealing with plant morphology. Thorough manufacturing details. Engineering details. Original collection of statistics. ARTICLES. ‘* Paper’ in Spon’s Encylopedia of Useful Arts. “Cellulose,” ‘‘ Paper.” Thorpe’s Dictionary of Chemistry. J OURNALS. Papermaker. Papermaking. Paper Trade Review. Paper, Box, and Bag Maker. Paper Trade Journal. Berlin. Papierzeitung. Papier Fabrikant. Wochenblatt fuer Papierfabrikation. New York. Biberach. INDEX ee A. AcETATES of cellulose, 36, 48 bibliography, 240 cost of production, 238 solvents, 238 Aceto-sulphates of cellulose, 49 Acid-sulphuric esters of cellulose, 48 Afforestation, 79—85 Aleohol from waste liquor, 128 Alkali-cellulose, 50 Alkalis, action upon cellulose, 52 sawdust, 199 sulphite Angiosperms, 4 Aniline sulphate, 114 Annual rings, 19 Aromatic bases, 70 Artificial silk, 41 Assimilating organs, 4 tissue, 16 Autoxidation, 29 B. BARKING machine, 96 Bast, 18 Beating, 184 . Beech wood, 29 Benzoates of cellulose, 86, 49 Beveridge, 134 Birdseye grain, 24 Bisulphites, 58 Bleaching of wood pulp, 147, 152, 173, 174 powder _ liquors, analysis, 147 consumption, 153—162 effect of keep- ing, 148 residual, 149 strength, 147 Board machines, 191, 192 Box-making, 193 Breaking length, 40 Breast roll, 187 Brown wood pulp, 109 Burr, 24 C. Catuuvs plate, 18 Calorific value of wood, 27 Cambium, 20 Canadian Forestry Convention, 82 Castner-Kellner system, 175 Cell, 9 Celluloid, 235 Cellulose, 29 acetates, 36, 48, 238, 240 266 Cellulose, acetates, bibliography, 240 aceto-sulphates, 49 acid-sulphuric esters, 48 action of alkalis, 52 benzoates, 86, 49 compound, 55 constitution, 46 decomposition, 54 denitration, 242 double salts, 86 esters, 36, 45, 47, 234, 242 group, 90 mixed esters, 50 nitrates, 36, 234, 242 oxidation, 52, 53 relative values of different forms, 249 solvents, 47 special industries, 234 Chemical wood pulp, 28, 120 history, 91 list of inventions, 28, 120 Chlorine, 58, 116, 165 Chromic acid, 538 Claviez system, 221 Cold ground pulp, 97 Collateral bundles, 21 Collenchyma, 16 Colloids, 33 Comparison of sulphite and soda wood papers, 185—140 Composition of sulphate liquor, 140 waste — sulphite liquor, 124 Compound celluloses, 55 Concentrator, 143 Conducting tissue, 13 Constitution of cellulose, 46 Cork, 15 Cortex, 15 INDEX Cost of afforestation, 83 Couch roll, 187 Cross and Bevan, 41 Crystalloids, 33 D. DENITRATION of cellulose, 242 Densities of various woods, 25 Destructive distillation, 54, 202 Dextion, 125 Dicotyledonous stem _ structure, 18 Dimethylparaphenylene diamine, 70, 114 Dorenfeldt, 126 EK. Economica bleaching conditions, 144 Eibel system, 188 Ekman and Fry, 94 Elasticity, 40 Electrical units, 1683—165 Electrolytes, 34, 165 Electrolytic bleaching, 162 Epidermis, 15 Exogenous stem, 19 Explosives, 239 Extensibility, 40 ie FELTING, 187 Ferments, action upon cellulose, 53 Fern, structural features, 3 Ferric-ferricyanide, 68, 114 INDEX 267 Fibres, 11 length of various, 215 Films, 43 photographic, 237 Forestry, 78 Fossil resins, 75 Fourdrinier paper machine, 187 Furfural, 55, 61 Gs GELATINE, 33 Ginning process, 219 Grain, 22 Grinder, 98 Gun-cotton, 234 Gymmnosperms, 4 lak Haas and Oettel apparatus, 166 Hardness of various woods, 26 Hargreaves-Bird process, 175 Heart wood, 20 Hemicellulose, 56 History of chemical pulp, 91 mechanical pulp, 90 Hoffmann, 124, 225 Hollander, 185 Hot ground pulp, 97 Houghton, 92 Humidity of atmosphere, effect upon various pulps, 213 Hydriodic acid, action cellulose, 638 Hydrobromic acid, action upon cellulose, 51 Hydrochloric acid, action upon cellulose, 52 Hydroxy furfurals, 70 Hypochlorites, action upon cellu- lose, 52 W.P. upon J. JORDAN refiner, 187 Jute fibre, 29 xanthogenic acid, 68 Ke KELLNER-TURK system, 222 Kirschner, 100—105 Kraft papers, 134 Kron system, 226 ai LIGNIFICATION, 29 Lignified vessels, 25 Ligno-cellulose, 80, 56—64 bleaching, 65—67 esters, 65 photochemical TL Lignone, 80, 57—64 action of bisulphites, 58 chlorine, 58, 116 constitution, 66 effect on chemical reactivity, 68 sulphonates, 65, 124 Lignorosin, 127 Lustra-cellulose, 42 phenomena, M. MaGnesium hypochlorite, 166 Manufacture of chemical wood pulp, 120 mechanical wood, 96 Marshall refiner, 187 Measurement of timber, equiva- lent table, 88 Ss) 268 Mechanical tissue, 18, 16 wood pulp, 27, 96 determination in papers, 111—119 manufacture, 96 output under varying condi- tions, 100—105 Medulla, 19 Medullary rays, 19, 24 Meristematic tissue, 20 Mestome, 13 Methoxyl, 63 Methyl groups, percentage in various woods, 64 Metrical yarn numbers, 231 Micro-chemical reactions of fibres, 113 Microscopic analysis, 112 Mixed esters of cellulose, 49, 50 Monocotyledonous stem struc- ture, 21, 22 Multiple effect evaporator, 1388 Ne 4 ‘‘ News”’ and Printings, 178 mill, economy in work- ing, 180 Newspaper, composition, 180 improvements in manufacture, 183 Nitrates of cellulose, 86 Nitric acid, 60 O. Osmasis, 34 Oxalic acid, 200 Oxidants, 52 Oxycellulose, 53 INDEX z, PapER pulp yarns, 220 Para-abietic acid, 22 Parenchyma, 12 Patent Spinnerei, 228 Pentosan, 62 Permanganates, cellulose, 52 Phenols, 69, 114 Phloem, 18 Phloro-glucinol, 69,114 Photo-chemical phenomena, 71 Photographie films, 237 Photosynthesis, 6 Physical properties of woods, 25 Pinchot, 81 action upon Pith, 19 flecks, 25 rays, 19 Pollution of streams, 129 Porion evaporator, 137 Power, 181 Printing papers, 70 Producer gas from wood, 200 Q. Quick cook process, 121 R. Reactions of decomposition, 51 Refiners, 187 Relation of yarn to paper, 218 Residual bleach liquors, 149 Russell, 29, 71 SAP wood, 20 Saponification, 48 Sawdust uses, 199 INDEX Schimmel, O., & Co., 223 Schuckert’s electrolyser, 172 Sclerenchyima, 16 Screening, 105 Secretionary products of plants, 25 Sheathing tissue, 16 Siemens & Halske electrolyser, 168 Sieve tube, 18 Silvalin yarns, 226 Slowcook process, 122 Soda process, 131 recovery, 136 Sodium hypochlorite, 163 Solvents of cellulose, 47 Sources of supply, 76 Spermatophytes, 3 Spinning of textile yarns, 217 Starch, 82 Steamed wood, 109 Stele, 15 Stem structure, contrast of monocoty! and dicotyl, 14 Stereome, 13 Strehlenert, 41 Strength of various woods, 26 wood pulp yarns, 228 Sugars, 34 Sulphate liquor, analysis, 140 process, 189 Sulphite liquor, 122 process, 121 Sulpho-carbonates, 39 Sulphuric acid, 51 Ate TEMPERLEY, 150 Tenacity, 40 Tensile strength, 40 269 Testing wood pulp for moisture, 206 Tetmayer, 26 Textile industries, 215 yarns from paper, 220 Tilghman, 92 Tintometer, 161 Tower system of bleaching, 142 Tracheex, 18 Tracheids, 18 ve VASCULAR tissue, 14 Vessels, 11 Viscose, 389, 48, 242—249 spinning, 245—247 W. WasHInG and finishing, 130 Waste sulphite liquors, 123 composition, 124 sizing products, 125 Wedge method of testing pulp, 209 Wet press machine, 108 Wood, 18 calorific value, 27 composition, 120 digestion in water, 109 standards of measurement, 85 Wood pulp bleaching, 141 boards, 190 chemical, 28, 120 list of inventions, 95 imports, 176 270 Wood pulp, mechanical, 27, 96, 100—105, 111—119 production in various countries, 77—79 sources of supply, 76 trees, 89 yarns, 220 cost of produc- tion, 229 physical proper- ties, 280 strength, 228 BRADBURY, AGNEW & CO. LD. INDEX Wood waste, utilisation, 198 wool, 199 ».G XANTHOGENIC ester of cellulose, 39, 43, 242, 2438 jute, 68 Xylem, 18 Xylolin, 222 Xylonite, 235 PRINTERS LONDON AND TONBRIDGE. SPECIMEN PAPER. Nowl: Trade Description. Heavy Imitation Art. 46 lbs. Demy = 480 sheets. (Messrs. Spalding & Hodge.) Price 23d. per Ib. RESULTS OF TEST. WEIGHT OF REAM. Demy 174"’ x 224’ = 480 sheets Gramines per square metre THICKNESS. Single sheet STRENGTH. Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction Tcl lleyey, Cross direction 9°3 lbs. Mean tensile strength of paper BREAKING LENGTH BREAKING WEIGHT PER SQ. MM. OF SECTIONAL AREA Loss oF STRENGTH DUE TO FOLDING, On folding 4 times mean % loss On folding 12 times mean % loss BuRSTING STRAIN, Lbs. per square inch required Grammes per square centimetre ASH. Percentage of loading ... FIBROUS COMPOSITION, Esparto _... Ane Sulphite Wood “46 lbs. ‘0058 ins. 11°7 lbs. 2269 yds. 51-395 65°0% 24:0 lbs. 30°4% 80% 20% 171°1 gms. ‘147 mm. 5°32 Kilos. 2073 Metres. 2413 gms. 1687 gms. VOLUME COMPOSITION. Grammes per C¢.Cc. Percentage composition by volume. Paper Fibre Ash Fibre 1163 “809 354 53°9 Ash Air space 14°2 | 31°9 = ae aoe ee fT ahayV . ‘ bah oe Se: . Napier SPECIMEN Paper. NO. 3. Trade Description. Sulphite Printing. 21 1bs. Demy = 480 sheets. (Messrs. Lepard & Smith.) Price 24d. per lb. RESULTS OF TEST. WEIGHT OF RAAM. Demy 173” x 223” = 480 sheets 21 Ibs. Grammes per square metre ... 78°1 gms. THICKNESS. Single sheet “o Le .. ‘0033 ins. °*084 mm. STRENGTH. Tensile strength on strips 15 mm. wide Machine direction 7-4 lbs. Cross direction 2p Dss Mean tensile strength of paper 5:0 lbs. 2°27 Kilos. BREAKING LENGTH .. ase ... 2125 yds. 1938 Metres BREAKING WEIGHT PER SQ. MM. OF SECTIONAL AREA ... : 1800 gms. Loss oF STRENGTH DUE TO FOLDING. On folding 4 times mean loss 34:0 °/, On folding 12 times mean loss 40-0 °/, BURSTING STRAIN. Lbs. per square inch required 9°5 lbs. Grammes per square centimetre 668 gms. ASH. Percentage of loading ... bao) DST FIBROUS COMPOSITION. Sulphite wood ... po 53 100 °/, VOLUME COMPOSITION. Percentage composition by volume. Grammes per €.c. Paper Fibre Ash Fibre Ash Air space 929 725 “204 48°3 8°2 43°5 SPECIMEN Paper. No. 4. Trade Description. Imitation Art. 22 lbs. Demy = 480 sheets. (Messrs. Lepard & Smiths, Ltd.) Price 28d. per lb. RESULTS OF TEST. WEIGHT OF REAM. . Demy 173” x 223” = 480 sheets 22 lbs. Grammes per square metre... 81°8 gms. THICKNESS. Single sheet “es a .. ‘0030 ins. °076mm. STRENGTH. Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction 9°4 lbs. Cross direction 4°7 lbs. Mean tensile strength of paper 7:1 lbs. 3°23 Kilos. BREAKING LENGTH .. aes .. 2880 yds. 2633 Metres. BREAKING WEIGHT PER SQ. MM. OF SECTIONAL AREA ... 2834 gms. Loss oF STRENGTH DUE TO FOLDING. On folding 4 times mean loss 549 °/, On folding 12 times mean loss 69:0 °/, BURSTING STRAIN. Lbs. per square inch required 15°1 lbs. Grammes per square centimetre 1055 gms. ASH. Percentage of loading .. She, eee Fiprous ComMposiTION. Esparto ... ies ond it 90 % Sulphite wood ... oe % LOM E VOLUME COMPOSITION. Percentage composition Gramm r ¢.e. BS, POPES by volume. Paper Fibre Ash Fibre Ash Air space 1-076 816 ‘260 54°4 10°4 35°2 SPECIMEN Paper. No. 5. Trade Description. Esparto Printing. 22 lbs. Demy = 480 sheets. (Messrs. Lepard & Smiths, Ltd.) Price 2Zd. per lb. RESULTS OF TEST. WeicHt oF REAM. Demy 173%” x 223’’ = 480 sheets 22 lbs. Grammes per square metre ..,. 81°8 gms. THICKNESS. Single sheet ae ae .. 0034ins. -*086 mm. STRENGTH. Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction 9°5 lbs. Cross direction Dro Lbs. Mean tensile strength of paper 7°4 Ibs. 3°37 kilos. BREAKING LENGTH ... =. ... 8002 yds. 2745 metres. BREAKING WEIGHT PER SQ. MM. OF SECTIONAL AREA ... : 2613 gms. Loss OF STRENGTH DUE TO FOLDING. On folding 4 times mean loss 324 °/, On folding 12 times mean loss 44°6 °/, BURSTING STRAIN. Lbs. per square inch required 17:2 lbs. Grammes per square centimetre 1198 gms. ASH. Percentage of loading ... sta DOSY fe FIBROUS COMPOSITION. Ksparto ... Bs a D4 80 °/, Sulphite wood ... hea ahs 20 Che VOLUME COMPOSITION. Grammies per ¢.¢. | Percentage composition by volume. Paper Fibre Ash Fibre Ash | Air space 952 ‘790 “162 52°7 6°5 | 40°8 ae ig / ’ Bi dig a ‘ “4 “ ‘ ie ee ee Se = - ps ie A 9 AS Dyine tp tens’ ro ad Zz 4 ee ae ey ; rs me tf vn utbe Vol 6 Cue Nee sa Sod ‘ Slee NY ey ; soe Cen) sit Ttee te OE =e ' ; £ a wit he OURAN Biys, ie 2 7 , - od i abi aily ah OR te ae tae ‘ * ee 2 be ; oe ip ice Na) ett LIS Saree are “i . : MG a Wn EA ¥ a Rea" raion old [2 GON ORE ee SER itt Grete pee ; Cray as ‘2 as eae gt “7 WE A ‘ : § Jae ; : ae 2 bs sn nS er f PEt te vay fu ny a rb Hz Wye tm / CLM, “Peres, 5 NW rie A as AM no aaa TTL ome ' > hin ; ‘ee cineki Sak % Lid ty aye ae mt OE wets ? ek Gee 4 ; we { meRiCg cube riy cht ase Tobe iy ae ve r eH Res Hit rlonhiE y ines" “a = ah. dtl’ NGPA) Bele ey ona eee Te thre eee Ot eee sy a rw: 4 : ~) 3 ” ‘ 2 \ ee ? CUPL CET, Sa aus Si res Sau ey Ea AE : : ee AR Ae TEE ert LH ONtARER 2d 71 bom S >, oF ah AH s FAP co VCK ; 7 Danie ac and Poa res ee "ee os ‘ a ; ‘2. ae 1 eng 27 st +> wh iii ye ‘ fy y 7 i ey : » Vat veck aan. eorth €L Eanitet Avr -e ‘ - ‘ : ‘i . i Kian ante s i ? 4 ' frei pry a ont Bee A Ge | xt , * an | j al & ( shy pe 6 7) "Lavi GAR ae a4 2 dal ES wy ri) ‘ “ a x fal : 2 ys : \ pra |. 7 .. ; 7 re \ VaNES vr) APLEDRADP ta) it eyita't 4 J aie - F is f , s * . x » j Pony #0’) : felt f bys ais SPECIMEN PAPER, No. 6. Trade Description. High-class Art Paper. 41 lbs. Demy = 480 sheets. Prices on application to Messrs. C. Morgan & Co. RESULTS OF TEST. WEIGHT OF REAM. Demy 173"’ x 224’’ = 480 sheets Grammies per square metre THICKNESS, Single Sheet oid aS STRENGTH. Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction 13°8 lbs. Cross direction 74 Ibs. Mean tensile strength of paper BREAKING LENGTH ... es ote BREAKING WEIGHT PER SQ. MM. OF SECTIONAL AREA Loss OF STRENGTH DUE TO FOLDING. On folding 4 times mean % loss On folding 12 times mean % loss BURSTING STRAIN. Lbs per square inch required Grammes per square centimetre ' ASH, ; Percentage of loading ... SIZING. Percentage of gelatine .., ase FIBROUS COMPOSITION. Esparto ... Zen wr ae Sulphite Wood ... ace be 41 lbs. *0052 ins. 10°6 lbs. 2306 yds. 49°1% 63°2% 23°3 lbs. 29:0% 5°43% 45% 55% 152°5 gyms. 132 mm. 4°85 Kilos. 2114 Metres. 2488 gms. VOLUME COMPOSITION, Grammes per ¢.c¢. Percentage composition by volume. : irene Gela- Fibre | Ash tine 063 Paper 1152 | °755 334 Fibre | Ash 50°3 | 13-4 Gela- | Air tine | space 4:7 31°6 SPECIMEN PAPER. No. 7. Trade Description. Common Art Paper. 388 lbs. Demy = 480 sheets. (Messrs. Lepard & Smiths.) Price 23d. per lb. RESULTS OF TEST. WEIGHT OF REAM. Demy 173"’ x 224'’ = 480 sheets 38 lbs. Grammes per square metre ... 141°4 gms. THICKNESS. Single sheet San ee PeNOODS Mise 135 mm. STRENGTH. Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction 11°8 lbs. Cross direction 4°8 lbs. Mean tensile strength of paper 8°3 lbs, 3°76 Kilos. BREAKING LENGTH ... as ... 1950 yds. 1778 Metres. BREAKING WEIGHT PER SQ. MM. OF SECTIONAL AREA ... Gs 1858 gms. Loss OF STRENGTH DUE TO FOLDING. On folding 4 times mean % loss = 410% On folding 12timesmean %loss 48:2% BURSTING STRAIN. Lbs. per square inch required 18°2 lbs. Gramumies per square centimetre 1275 gms. ASH. Percentage of loading ... 3 28°3% SIZING. Percentage of gelatine... eS SOU FIBROUS COMPOSITION. Sulphite Wood .., 8 Ss 90% Mechanical Wood Suis a 10% VOLUME COMPOSITION, Percentage composition Grammes per ¢.c. by volume. ee 2 Gela- ; Gela- | Air Paper | Fibre | Ash ihe, Fibre | Ash tine. | space. 1:047 | °710 ‘296 041 47°3 11°8 3°0 37°9 mS +3 C= be RESULTS OF TEST. ‘Weicnr oF “Raat. Demy 173" x 224'' = 480 cHowtne 14 lbs. - Grammes per pees metres. so THICKNESS. Z _ Single sheet Was ski 0041 ins. _ greenorn. Tensile strength on attra 15 mm. wide (Leunig’s machine) — Machine direction =~ 5*51bs. © Cross direction — 2°4 lbs. “ Mean tensile strength of paper 4°0lbs. — 1°81 Kilos. Breakina LENGTH... ... ... 2550 yds. 2324 Metres, EIS ae WEIGHT OF SQ. MM, OF SECTIONAL AREA... _... . 1161 gms, roe OF : STRENGTH DUE TO FoLDING. 3 On folding 4 timesmean % loss 10°:0% On folding 12 times mean % lose 20°0% Bursting STRAIN. | Libs. per square inch heats 81 lbs. Grammes per square centimetre ASH, ean Seek Percentage of loading ee 42% FrBrovs CoMPOSITION. : * - Sulphite wood .... 10% Mechanical wood 90% _ VOLUME’ CoMPOSITION, ee Percentage composition ee per ¢.c. “by volume. Paper | Fibre. Ash | Fibre | Ash | Airspace 500 ‘479 ‘O21 | 819 0°84 67°3 By ar Ay sf x 50 SercrmEN Paper. No. 9. Trade Description. High-class News. 18 lbs. Demy = 480 sheets. Prices on application to Messrs, C. Morgan & Co. RESULTS OF TEST. WEIGHT OF REAM. Demy 174" x 224’ = 480sheets 18 lbs. Grammes per square metre ... 67°0 gms, THICKNESS, Single sheet... act ». 0045 ins. 114 mm. STRENGTH Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction 6°3 lbs. Cross direction 4°1 lbs. Mean tensile strength of paper 5:2 lbs. 2°36 Kilos. BREAKING LENGTH ... sen ... 2578 yds. 2350 Metres. BREAKING WEIGHT PER SQ. MM. OF SEcTIONAL AREA ... ae 1878 gms. Loss or STRENGTH DUE TO FOLDING. On folding 4 times mean % loss 154% On folding12timesmean%loss 19°2% Bourstine STRAIN. Lbs. per square inch required 11°4 lbs, Grammes per square centimetre 808 gms. ASH. Percentage of loading ... ph 3°3% Fisrovus COMPOSITION. Sulphite Wood ... i Res 80% Mechanical Wood oe pan 20% VOLUME COMPOSITION. ‘ Grammes per ¢.c Percentage composition by volume. Paper | Fibre Ash Fibre Ash _ |Air space 587 568 019 37°9 08 61°3 SPECIMEN Paper. No. 10. Trade Description. Bulking Antique Wove Printing. 18 lbs. Demy = 480 sheets. Prices on application to Messrs. C. Morgan & Co. RESULTS OF TEST. Wriant or Ream. Demy 174" x 224'’ = 480sheets 18 lbs, Grammes per square metre ... 67°0 gms, THICKNESS. Single sheet ode ao ... °0066 ins. "168 mm, STRENGTH. Tensile strength on strips 15mm. wide (Leunig’s machine) Machine direction 7°7 lbs. Cross direction 4°2 lbs. Mean tensile strength of paper _6°0 lbs. 2°72 Kilos. BREAKING LENGTH ... tee ... 2975 yds. 2710 Metres. BREAKING WEIGHT PER SQ. MM, OF SECTIONAL AREA ... ae 1081 gms. Loss OF STRENGTH DUE TO FOLDING. On folding 4timesmean% loss 35°0% Onfolding12timesmean%loss 41°7% Bursting STRAIN. Lbs. per square inch required 13:1 lbs. Grammes per square centimetre 914 gms. ASH. Percentage of loading ... ie 75% Fisrovus CoMPosirTIon. Esparto ... seh ies ses 95% Sulphite Wood ... ee me 5% VOLUME COMPOSITION. Grammes per ¢.c. Percentage composition by volume. Paper Fibre Ash Fibre Ash _ Air space “400 °370 030 24°7 12 74:1 Oy ibe ils. eee IO IN il SPECIMEN Paper. No. 11. Trade Description. Cartridge. (Messrs. Lepard & Smiths.) Price 23d, per lb. RESULTS OF TEST. WEIGHT OF REAM. Demy 174"’ x 223'/' = 480sheets 29 lbs. Grammes per square metre THICKNESS. Single sheet As ae .. °0055 ins. STRENGTH. Tensile strength on strips 15 mm. wide (Leunig’s machine) Machine direction 14°5 lbs, Cross direction 5°8 lbs. Mean tensile strength of paper 10:2 lbs. BREAKING LENGTH ... 8139 yds. BREAKING WEIGHT PER SQ. MM, OF SECTIONAL AREA ... - Loss or STRENGTH DUE TO FOLDING. On folding 4 times mean % loss 30°4% On folding12timesmean%loss 40°2% BurRsTING STRAIN. Lbs. per square inch required 19°8 lbs, Grammes persquare centimetre ASH. Percentage of loading ... 9:5% Fisrous CoMPOSITION. Sulphite wood oe Ae 99% Mechanical wood ao or 1% VOLUME COMPOSITION. Grammes per C.C¢. Ash 073 Fibre 46°5 Fibre 698 Paper ‘T71 Ash 29 lbs. Demy = 480 sheets. 107°9 gms, "140 mm. 4°63 Kilos. 2865 Metres. 2207 gms 1391 gms. Percentage composition by volume. Air space 50°6 Y SAU eae hae a “f : sey use Mt ae pratt ere WF <- 4 pe © - time e a As ud » io ae eel ‘ ey Wikete, nels * vm eo te . AN tig Laie , upe Sipe § tig ” —_ 7, res a 3, wie? ‘ : - or ae Nee mae i% ; “m oe ; - Sy " . ie YAnfile Wie Ot SEG our 4 one ee &su'e ahi roses j Og, ae ‘ . a wes aA & % oe et Ln ; LS getiest i Cher abhi > ' ri <<. “ . £ , we : Pere ef ithe *5 Liebe wort Choe og e at Sea ; aeF 8) rel prpntt ty reds hh BF eee, ; et al Ara Ratner th, ciert $ Si*2s «9 . , ‘ a4 f >a od Pj def C4 ep on fp tet linge ade: ee Se al eins oe ae ae y f yeas. >. re: ? ees SE ee Pol Fs Om , a 40 eee ; i oe Bite Pree ’ t 49 Be" aes PTR eee F ‘ we y ~, . Fp alge “i f . ‘ # ;: ears ‘ ‘ ca ¥ oe Treeverses : wy y = i ee ' P ‘ ‘ me ’ rr . Se i ie ‘ - 2 Pt Fes 1, ere ee ve a re - J 6 jonge Pore, - me SY TRS 1 MEA ES BAe nese oe mifeor + Dotvwr dont suprise ahh yg So eS mi ae ge ei \ Wir will AS Obagi’! 4; » a t “ t , ore ' e's : —— < ‘ a 4 VAN NOSTRAND'S “WESTMINSTER” SERIES Bound in Uniform Biyles | Fully Illustrated. Price $2.00 net each. Gas Engines. By W. J.. MARSHALL, Assoc. M.I.Mech.E., apd CApT. H. RIALL SANKEY, RE. (Re¢t.).. M.Inst.C.E., M.I.Mech.E. 300 Pages, 127 Illustrations. List oF ConTENTS : Theory of the Gas Engine:. The Otto Cycle. The Two Stroke Cycle. Water Cooling of Gas Engine Parts. Ignition. Operating Gas Engines. The Arrangement of a Gas Engine Instal- lation. The Testing of Gas Engines. Governing. Gas and Gas mProducers.” index. Textiles. By A. F. Barxer, M.Sc., with Chapters on the Mercerized and Artificial Fibres, and the Dyeing of Textile. Materials by W. M. GARDNER, M.Sc., F.CS.; Silk Throwing and Spinning, by R. SNow ; the Cotton Industry, by W. H. Cook; the Linen Industry, by F >: BRADBURY. 370 Pages. . 86 Illustrations. ConTEnTS: The History of the Textile Industries ; also of Textile Inventions and Inventors. The Wool, Silk, Cotton, Flax, etc., Growing Industries. The Mercerized, and Artificial Fibres em- ployed in the Textile Industries. The Dyeing of Textile Materials. The Principles of Spinning. Processes preparatory to Spinning. The Principles of Weaving. The Principles of Designing and Colouring. The Principles of Finishing. Textile Calculations. The Woollen Industry. The Worsted Industry. The Dress Goods, Stuff, and Linings Industry. The Tapestry and Carpet Industry. Silk Throwing and Spinning. The Cotton Industry. The Linen Industry historically and commercially ; considered. Recent Developments and. the Future of the Textile Industries. Index. Soils and Manures. By J. Aran Murray, B.Sc. 367 Pages. 33 Illustrations.. - ConTENTS: Introductory. The Origin of Soils. Physical Pores ties of Soils: Chemistry of Soils. Biology. of Soils. Fertility. Principles of: Manuring. Phosphatic’ Manures.. Phosphonitro- genous Manures. WNitrogenous. Manures. Potash Manures. Compound and Miscellaneous Manures.. General Manures. Farm- yard Manure. Valuation of Manures. Composition and Manural Value of Various Farm Foods. (1) THE ““WESTMINSTER? 7 SE Ries Gout By James ToncE, M.I.M.E., F.G.S., etc. (Lecturer on Mining at Victoria University, Manchester). 283 Pages. With 46 Illustrations, many of them showing the Fossils found in the Coal Measures. List oF CONTENTS: History. Occurrence. Mode of Formation of Coal Seams. Fossils of the Coal Measures. Botany of the Coal-Measure Plants. Coalfields of the British Isles. Foreign Coalfields. The Classification of Coals. The Valuation of Coal. Foreign Coals and their Values. Uses of Coal. The Production of Heat from Coal. Waste of Coal. The Preparation of Coal for the Market. Coaling Stations of the World. Index. Iron and Steel. By J. H. Sranssre, B.Sc. (Lond.), F.I.C. 385 Pages. With 86 Illustrations. List oF CONTENTS: Introductory. Iron Ores. Combustible and other materials used in Iron and Steel Manufacture. Primitive Methods of Iron and Steel Production. Pig Iron and its Manu- facture. The Refining of Pig Iron in Small Charges. Crucible and Weld Steel. The Bessemer Process. The Open Hearth Process. Mechanical Treatment of Iron and Steel. Physical and Mechanical Properties of Iron and Steel. Iron and Steel under the Microscope. Heat Treatment of Iron and Steel. Elec- tric Smelting. Special Steels. Index. Timber. By J. R. BaterpEN, Assoc.M.Inst.C.E. 334 Pages. 54 Illustrations. | ConTENTS: Timber. The World’s Forest Supply. Quantities of Timber used. Timber imports into Great Britain. European Timber. Timber of the United States and Canada. Timbers of South America, Central America, and West India Islands. Tim- bers of India, Burma, and Andaman Islands. Timber of the Straits Settlements, Malay Peninsula, Japan and South and West Africa. Australian Timbers. Timbers of New Zealand and Tasmania. Causes of Decay and Destruction of Timber. Seasoning and Impregnation of Timber. Defects in Timber and General Notes. Strength and Testing of Timber. ‘“ Figure” in Timber. Appendix. Bibliography. Natural Sources of Power. By Rosert S. BALL, B.Sc., A.M.Inst.C.E. 362 Pages. With 104 Diagrams and Illustrations. CoNnTENTS: Preface. Units with Metric Equivalents and Abbre- viations. Length and Distance. Surface and Area. Volumes. Weights or Measures. Pressures. Linear Velocities, Angular Velocities. Acceleration. Energy. Power. Introductory Water Power and Methods of Measuring. Application of Water Power to the Propulsion of Machinery. The Hydraulic Turbine, (24) THE “ WESTMINSTER” SERIES asa, es aS Various Types of Turbine. Construction of Water Power Plants. Water Power Installations. The Regulation of Turbines. Wind Pressure, Velocity, and Methods of Measuring. The Application of Wind Power to Industry. The Modern Windmill. Con- structional Details. Power of Modern Windmills. Appendices. A, B,C. Index. Electric Lamps. By Maurice Sotomon, A.C.G.I., A.M.I.E.E. 339 Pages. 112 Illustrations. ConTENTS: The Principles of Artificial |llumination. The Produc- tion of Artificial Illumination. Photometry. Methods of Testing. Carbon Filament Lamps. The Nernst Lamp. Metallic Filament Lamps. The Electric Arc. The Manufacture and Testing of Arc Lamp Carbons. Arc Lamps. Miscellaneous Lamps, Compari- son of Lamps of Different Types. Liquid and Gaseous Fuels, and the Part they play in Modern Power Production. By Professor ViviAN B. Lewes, F.IL.C., F.C.S., Prof. of Chemistry, Royal Naval College, Greenwich. 350 Pages. With 54 Illustrations. List OF CONTENTS: Lavoisier’s Discovery of the Nature of Com- bustion, etc. The Cycle of Animal and Vegetable Life. Method of determining Calorific Value. The Discovery of Petroleum in America. Oil Lamps, etc. The History of Coal Gas. Calorific Value of Coal Gas and its Constituents. The History of Water Gas. Incomplete Combustion. Comparison of the Thermal Values of our Fuels, etc. Appendix. Bibliography. Index. Electric Power and Traction. By F. H. Davies, A.M.I.E.E. 299 Pages. With 66 Illustrations. List oF CONTENTS: Introduction, The Generation and Distri- bution of Power. The Electric Motor. The Application of Electric Power. Electric Power in Collieries. Electric Power in Engineering Workshops. Electric Power in Textile Factories. Electric Power in the Printing Trade. Electric Power at Sea. Electric Power on Canals. Electric Traction. The Overhead System and Track Work. The Conduit System. The Surface Contact System. Car Building and Equipment. Electric Rail- ways. Glossary. Index. Decorative Glass Processes. By Arruur Louis DUTHIE. 279 Pages. 38 Illustrations. ConTENTS: Introduction. Various Kinds of Glass in Use: Their Characteristics, Comparative Price, etc. Leaded Lights. Stained Glass. Embossed Glass. Brilliant Cutting and Bevelling. Sand- Blast and Crystalline Giass. Gilding. Silvering and Mosatc. Proprietary Processes. Patents. Glossary. (3°) _FHE “WESTMINSTER” SERIES Tae Gas and its Uses for the Production of Light, Heat, and Motive Power. By W. H. Y. WeBBER, C.F. 282 Pages. “With 71 Illustrations, ‘List oF ContENTS: The Nature and Properties of Town Gas. The History and Manufacture of Town Gas. The Bye-Products of ’ Coal Gas: Manufacture. Gas Lights’ and Lighting. Practical Gas Lighting.. The Cost of Gas Lighting. Heating and Warm- ing by Gas. Cooking by Gas. The Healthfulness and Safety of Gas in all-its uses. Town Gas for Power Generation} including Private Electricity Supply. The Legal Relations of Gas Sup- pliers, Consumers, ‘and the Public. Index. Electro-Metallurey. By J. B. C. Kersnaw, F.C. 318 Pages. With 61 Illustrations. ; --CONTENTS: Introduction and Historical Survey. Aluminium. Production, Details of Processes and Works. Costs. Utiliza- - tion: ‘Future of the Metal. Bullion and Gold. Silver Refining Process.: Gold Refining Procéssés. Gold Extraction Processes. Calcium Carbide and Acetylene Gas. The Carbide Furnace and Process. Production. Utilization. Carborundum. Details of Manufacture. Properties and Uses. Copper. Copper Refin- “ing. Descriptions of Refineries. Costs. Properties and Utiliza- tion. .The Elmore and similar Processes. Electrolytic Extrac- ‘ tion ‘Processes. .Electro-Metallurgical Concentration Processes. Ferro-alloys:' Descriptions of Works. Utilization. Glass and Quartz Glass! Graphite... Details of Process. Utilization. ‘Iron and Steel. Descriptions.of Furnaces and Processes. Yields!and Costs. Comparative Costs. Lead. The Salom Process. The Betts Refining Process. The Betts Reduction Process. White Lead Pro- “cesses. _ Miscellaneous Products. Calcium. Carbon Bisulphide. Carbon Tetra-Chloride.. Diamantine. Magnesium, Phosphorus. Silicon and its Compounds, Nickel. Wet Processes. Dry Processes. Sodium. Descriptions of Cells and Processes. Tin. Alkaline Processes for Tin Stripping. Acid Processes for Tin Stripping. Salt Processes for Tin Stripping. Zinc. Wet Pro- cesses. Dry Processes. Electro-Thermal Processes. Electro- Galvanizing. Glossary. Name Index. Radio- Tele eRTAP OY. Bye Go E. Monckton, M.LE.E. ' 389 Pages. ith 173 Diagrams and Illustrations. CONTENTS : Preface. Electric Phenomena. Electric Vibrations. ' Electro-Magnetic Waves. Modified Hertz Waves used in Radio-. Telegraphy. Apparatus used for Charging the Oscillator. ; The Electric Oscillator : Methods of Arrangement, Practical Details. mabe Receiver: Methods of Arrangement, The Detecting Ap- *"paratus,,and other-details.. Measurements in ‘Radio-Telegraphy. ‘The Experimental Station at Elmers End: Lodge-Muirhead “System. -Radio- Telegraph Station at Nauen: Telefunken System. Station at Lyngby: Poulsen System. The Lodge- (4 ) THE “WESTMINSTER” SERIES Muirhead System, the Marconi System, Telefunken System, and Poulsen System. Portable Stations. Radio-Telephony, Ap- pendices: The Morse Alphabet. Electrical Units used ih this Book. International Control of Radio- -Telegraphy. Index. es Rubber and its Manufacture, with Chapters on Gutta-Percha and Balata. By H. L. Terry, _ F.I.C., Assoc. Inst. M.M: ' 303: ‘Pages. With Illustrations: List. or ContTENTS: Preface. Introduction: Historical and General. Raw/Rubber. ‘Botanical Origin. Tapping. the Trees. Coagulation.. Principal Raw Rubbers of Commerce. Pseudo- Rubbers. Congo Rubber, General’’'Considerations. Chemical and Physical Properties, Vulcanization. India-rubber Planta- ‘tions. India-rubber Substitutes. Reclaimed Rubber. Washing and Drying of Raw, Rubber, ‘Compounding of Rubber. Rubber Solvents and their Recovery. Rubber Solution. Fine Cut. Sheet and Articles made therefrom. Elastic Thread. Mechanical Rubber Goods. Sundry Rubber Articles. India-rubber Proofed Textures. Tyres. India-rubber Boots and Shoes.. Rubber for Insulated Wires. Vulcanite Contracts for India-rubber Goods. The Testing of Rubber Goods. Gutta-Percha. Balata. Biblio- graphy. Index, caer ge (3 ’ The Railway eceiictive: What It Is, and Why It is What It. Is.. By ‘VAUGHAN. PENDRED, M.Inst.M.E., Mem.Inst.M.I. 321 Pages... 94 Illustrations. ContTENTS : The Locomotive Engine as a Vehicle—Frames. Bogies. The Action of the Bogie. Centre of Gravity. Wheels. Wheel ‘and Rail. Adhesion. ‘Propulsion. Counter-Balancing. | The Loco- motive as a Steam Generator—The Boiler. The Construction of the -Boiler.. Stay ~Bolts. The Fire-Box. ‘The Design of Boilers. - Combustion. Fuel. ‘The Front End. The. Blast’ ‘Pipe. ‘Steam Water. Priming. The Quality of Steam. Superheating. Boiler Fittings. The Injector. The Locomotive as a+Steam ’ Engine— ‘Cylinders and Valves. ‘Friction. Valve Gear. Expansion. The Stephenson Link Motion. Walschaert’s: and Joy’s Gears. Slide Valves. Compounding, Piston Valves,’ The Indicator. Ten- ders, Tank Engines: ‘Lubrication. Brakes. The Running Shed. The Work of the Locomotive. eh | Glass Manufacture. By Watter RosENHAIN, Superin- tendent of ‘the Department of Metallurgy in the National Physical Laboratory, late Scientific Adviser in the Glass Works of: Messrs. Chance Bros.’ & Co. ise Pages. With Illustrations. ConTENTS Preface. Definitions. Physical and Chemical Qualities, Mechanical, Thermal, and Electrical Properties. Transparency 5”) THE “WESTMINSTER ” .SERIES and Colour. Raw materials of manufacture. Crucibles and Furnaces for Fusion. Process of Fusion. Processes used in | Working of Glass. Bottle. Blown and Pressed. Rolled or Plate. Sheet and Crown. Coloured. Optical Glass: Nature and Properties, Manufacture. Miscellaneous Products. Ap- pendix. Bibliography of Glass Manufacture. Index —. Precious Stones. By W. Goopcuizp, M.B., B.Ch. 3109 Pages. With 42 Illustrations. With a Chapter on Artificial Stones. By RosBert Dykes. 7 List oF CONTENTS: Introductory and Historical. Genesis cf Precious Stones. Physical Properties. The Cutting and Polish- ing of Gems. Imitation Gems and the Artificial Production of Precious Stones, The Diamond. Fluor Spar and the Forms of Silica. Corundum, including Ruby and Sapphire. Spinel and Chrysoberyl. The Carbonates and the Felspars. The Pyroxene and Amphibole Groups. Beryl, Cordierite, Lapis Lazuli and the Garnets. Olivine, Topaz, Tourmaline and other Silicates. Phos- phates, Sulphates, and Carbon Compounds. INTRODUCTION TO THE Chemistry and Physics of Building Materials. By ALAN E. Munsy, M.A. 365 Pages. Illustrated. ConTENTS: Elementary Science: Natural Laws and Scientific In- vestigations, Measurement and the. Properties of Matter. Air and Combustion. Nature and Measurement of Heat and Its Effects on Materials. Chemical Signs and Calculations. Water and Its Impurities. Sulphur and the Nature of Acids and Bases. Coal and Its Products. Outlines of Geology. Building Materials : The Constituents of Stones, Clays and Cementing Materials. Clas- sification, Examination and Testing of Stones, Brick and Other Clays. Kiln Reactions and the Properties of Burnt Clays. Plasters and Limes. Cements. Theories upon the Setting of Plasters and Hydraulic Materials. Artificial Stone. Oxychloride Cement. Asphaite. General Properties of Metals. Iron and Steel. Other Metals and Alloys. Timber. Paints: Oils, Thinners and Varnishes; Bases, Pigments and Driers. Patents, Designs and Trade Marks: The Law and Commercial Usage. By KEnnetu R. Swan, B.A. (Oxon.), of the Inner Temple, Barrister-at-Law. 402 Pages. ConTENTS: Table of Cases Cited—Part I.—Letters Patent. Intro- duction. General. Historical. I., II., III. Invention, Novelty, (6 ) THE “WESTMINSTER ”: SERIES Subject Matter, and Utility the Essentials of Patentable Invention. IV. Specification. V. Construction of Specification. VI. Who May Apply for a Patent. VII. Application and Grant. VIII. Opposition. IX. Patent Rights. Legal Value. Commercial Value.’ X. Amendment. XI. Infringement of Patent. XII. Action for Infringement. XIII. Action to Restrain Threats. XIV. Negotiation of Patents by Sale and Licence. XV. Limita- tions on Patent Right. XVI. Revocation. XVII. Prolonga- tion. XVIII. Miscellaneous. XIX. Foreign Patents... XX. Foreign Patent Laws: United States of America. Germany. France. Table of Cost, etc., of Foreign Patents. APPENDIx A.— 1. Table of Forms and Fees. 2. Cost of Obtaining a British Patent. 3. Convention Countries. Part II.—Copyright in Design. Introduction. I. Registrable Designs. II. Registra- tion. III. Marking. IV. Infringement. APPENDIx B.—1. Table of Forms and Fees. 2. Classification of Goods. Part III.—Tvrade Marks. Introduction. I. Meaning of Trade Mark. II. Qualification for Registration. III. Restrictions on Regis- tration. IV. Registration. V. Effect of Registration. VI. Miscellaneous. APPENDIx C.—Table of Forms and Fees, INDICEs. 1. Patents. 2. Designs. 3. Trade Marks. The Book: Its History and Development. By Cyrit Davenport, V.D., F.S.A. 266 Pages. With 7 Plates and 126 Figures in the text. List oF CONTENTS: Early Records. Rolls, Books and Book bindings. Paper. Printing. Illustrations. Miscellanea. Leathers. The Ornamentation of Leather Bookbindings without Gold. The Ornamentation of Leather Bookbindings with Gold. Bibliography. Index. The Manufacture of Paper. By R.W.SinpAtt, F.CS., Consulting Chemist to the Wood Pulp and Paper Trades ; Lecturer on Paper-making for the Hertfordshire County Council, the Bucks County Council, the Printing and Stationery Trades at Exeter Hall (1903-4), the Institute of Printers; Technical Adviser to the Government of India, 1905. 275 Pages. 58 Illustrations. ConTENTS: Preface. List of Illustrations. Historical Notice. Cel- lulose and Paper-making Fibres. The Manufacture of Paper from Rags, Esparto and Straw. Wood Pulp and Wood Pulp Papers. Brown Papers and Boards. Special kinds of Paper. Chemicals used in Paper-making. The Process of “ Beating.”” The Dye- ing and Colouring of Paper Pulp. Paper Mill Machinery. The Deterioration of Paper. Bibliography. Index. () THE ‘““WESTMINSTER” SERIES Wood Pulp and its Applications. By C. F. Cross, B.Sc., F.LC.,-E. J. BEVAN,-F.I.C.,-'and R:. W. SINDALL, F.C.S. 266 pages. 36 Illustrations. ContTENTs: The Structural Elements of Wood. Cellulose as a Chemical. Sources of Supply. Mechanical Wood Pulp. Chemical Wood Pulp. The Bleaching of Wood Pulp. News and Printings. Wood Pulp Boards. Utilisation of Wood Waste. Testing of Wood Pulp for Moisture. Wood Pulp and the Textile Industries, Bibliography. Index. © | Photography: its Principles and Applications. By ALFRED WATKINS, F.R.P.S. 342 pages. 98 Illus- trations. ‘- ConrTENTS: First Principles. Lenses. Exposure Influences. ‘Prac- tical Exposure: Development Influences. Practical Develop- ment. Cameras and Dark Room. Orthochromatic Photography. Printing Processes. Hand Camera Work. Enlarging and Slide Making. Colour Photography. General Applications. Record Applications, Science Applications. Plate Speed Testing. Pro- cess Work. Addenda. Index. IN PREPARATION. Commercial Paints and Painting. By A. S. Jenn- ~ InGS, Hon. Consulting Examiner, City, and Guilds of _ London Institute. | i Brewing and Distilling. 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