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 CHILD ACME CUTTER AND PRESS CO. 
 
 NEW YORK OFFICE, 12 READE STREET, 
 
 O. C. A. CHILD, Manager. 
 
 Factory and Main Office, 33. 35 and 37 KEMBLE ST. 
 
 BOSTON, MASS., U. S. A. 
 
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 MARKS Are Y aIuab1 ^ 
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 MARKS H Should be 
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THE flANUFACTURE OF 
 
 CELLULOSE. 
 
 A Practical Treatise for Paper and Cellulose Tech. 
 nologists, Managers and Superintendents, 
 
 BY 
 
 / 
 
 MAX SCHUBERT, 
 
 Royal Polytechnical School, Dresden. 
 
 Specially Translated for The American Paper Trade. 
 107 ILLUSTRATIONS. 
 
 ANDREW GEYER, 
 
 318 Broadway. New York. 
 
THE LIBRARY OF 
 CONGRESS, 
 
 Two Copies Received 
 
 JUL 5 1901 
 
 Copyright entry 
 
 CfcASS ■**«. N» 
 
 COPY B. 
 
 A h 
 
 1- 
 
 COPYRIGHTED 1899 
 
 BY 
 
 ANDREW GEYER. 
 
♦fjfiEFOKE complying with the request of Herr Fisher, 
 •^ publisher in Berlin, to compile for his technological 
 library, a small work on "the manufacture of cellulose," 
 I have first considered whether there existed a necessity 
 for such. ■ Although several short treatises on the com- 
 paratively new industrial branch, "the manufacture of cel- 
 lulose" have already appeared, the main published infor- 
 . mation has been in the several volumes of the Papier Zei- 
 tung, and other trade journals which contain a number of 
 articles about special departments of the industry and re- 
 lating questions. The above mentioned compilations are 
 treated in a general way and are short, forming chapters 
 of larger works on the manufacture of paper, while the 
 different articles in the papers are so much distributed 
 among others, partly also connected with personal contro- 
 versies and views, that I have become convinced of the 
 necessity and the meritoriousness of the labor. To sift this 
 comparatively valuable material, to complete it with per- 
 sonal experiences, and by adding practical advice, to create 
 an up to date book on the subject of "Cellulose" seemed to 
 me eminently desirable and I therefore seized with eager- 
 ness the task assigned me. I also communicated with 
 some men closely connected with the manufacture of cellu- 
 lose, and to them I am obliged for valuable details. I have 
 found, however, that it is impossible to give an entirely 
 exhaustive account of this branch, because not only are 
 the many different systems in use in the manufacture of 
 cellulose patented, but almost every manufacturer endeav- 
 ors to invest his process with all possible secrecy. I have 
 consequently treated copiously but one of the best intro- 
 duced processes, and the others I have but touched, sketch- 
 ing in the principal features of each. 
 
 In starting the book I adopted the principle of treating 
 the manufacture in its successive phases, and with each 
 chapter to consider the peculiarities of the different sys- 
 tems one after the other. In this manner I have avoided 
 repetitions, as some manipulations in the manufacture of 
 cellulose are the same in all processes, especially as to the 
 
4 PREFACE. 
 
 beginning with the pulp wood as well as the finishing of 
 the cellulose for shipping. 
 
 First of all the hook treats of the raw material, the 
 wood, with a description of the machinery necessary in it, 
 and then passes over to the preparation of the leaches. 
 Xext the soda process is treated in connection with the re- 
 generation of the soda and thereafter the sulphite process 
 is considered in its different variations and latest improve- 
 ments by text and illustration. The description of the 
 processes of boiling in the different systems preceeds the 
 consideration of the boilers as differing in size, form, 
 material and lining, and the methods for the finishing of 
 the products follow. 
 
 A higher value, however, than on the description of 
 manufacture proper and of the necessary apparatus and 
 machines is to be placed on the open discussion, contained 
 in the last chapter, of the difficulties, which are encoun- 
 tered in the manufacture of cellulose in the riddance and 
 harmless disposal of the spent liquors and offensive gasses. 
 The same is true of the practical advice which is ,given in 
 regard to planning of new factories. The liberal use of cel- 
 lulose has already caused a revolution in the extensive' pa- 
 per industry, as it is no longer absolutely necessary to look 
 for accommodations of large water power, or to provide 
 extensive rag lofts; because with steadily advancing im- 
 provement in cellulose its use will still grow. Consequently 
 the circle of all those who are interested in learning the 
 particulars about the production of cellulose and its prop- 
 erties must expand. 
 
 The expectation of success of the present book, as ex- 
 pressed in the preface to the first edition, has fortunately 
 become fulfilled to me as well as the publisher; for be- 
 sides the congratulations sent me from different sides, 
 shortly after the publication, a French translation was 
 prepared by the well known publishers, Baudry & Cie, in 
 Paris, edited by sub-director Mods. B. Bibas. Almost at 
 the same time I was negotiating for the preparation of a 
 Russian edition with a Russian engineer, but I do not 
 know whether the translation was executed, as on my men- 
 tioning of a trifling consideration, the correspondence 
 from that side was cut off, and Germany is not in literary 
 convention with Russia. Moreover, the entire edition was 
 sold out in two years, so that many orders could not be 
 
PREFACE. 5 
 
 accepted. Outside causes were responsible for the long de- 
 lay of the publication of the completed edition of this 
 work. 
 
 During the last four years, although no n^w processes 
 appeared in the manufacture of cellulose, a considerable 
 number of changes and improvements were made, which 
 deserved mention in the new edition. Those, therefore, 
 besides the personal practical experience recently obtained 
 have been incorporated in the new edition. I have also 
 used all information which was furnished to me by the 
 several inventors of the processes and the manufactures of 
 machinery, and also, as in the first edition, several arti- 
 cles and sketches from the last volumes of the Papier 
 Zeitung. In the new book the representation of the cell- 
 stuff manufacture is so supplemented and rendered up to 
 date and complete that instead of fifty-seven illustrations 
 107 figures are now necessary to supplement the descrip- 
 tions. 
 
 I hope that the second edition of my work will fully 
 meet its claim of offering in handy form all the informa- 
 tion that is desirable to the technologist. 
 
 Dresden. September 1896. 
 
 MAX SCHUBEET. 
 
I MANUFACTURE OF CELLULOSE. 
 
 Cellulose or wood fibre is one of the most important ami 
 most extensively diffused substances throughout nature 
 produced during milenaries by the activity of the plants, 
 stored up, though changed by terrestrial revolutions, in the 
 I'm m ol coal and continuously renewed by the present- 
 flora. Consideration of the immense variety of these pro- 
 ducers explains why wood fibre in a mechanical and chem- 
 ical sense also shows great differences, so that the name 
 wend fibre is really hut' an appelative, and for proper de- 
 scription the origin should be affixed every time, as has al- 
 ready been proposed from different sides. As, however, in 
 practice but few kinds of fibre enter into question, namely, 
 wood, straw and esparto, and as this book treats of the 
 most important only which is ligneous fibre, the designa- 
 tion wood fibre will suffice, and when the more frequently 
 used synonymous expression, "Cellulose" is employed, it 
 should always be understood as wood fibre. The expression 
 cellulose has first been used by Tessie du Motay. 
 
 With the exception of cotton the vegetable fibre is sel- 
 dom found exposed, but is enclosed by different more or 
 less -olid )le incTusting accessories. Mechanical disintegra- 
 tion of the wood does not separate them, although it fur- 
 nishes as wood, pulp a product, which on account of its 
 cheapness, has been of great use to the paper industry, be- 
 cause it has made possible the production in large quanti- 
 ties of low grade printing paper. The short quality of 
 ground wood pulp, its stiffness, poor felting capacity and 
 its resistance to bleaching agents prevent it from becom- 
 ing a, substitute for wood fibre. Sot until we succeeded in 
 freeing the wood fibre from its incrustation by chemical 
 means, and on a large scale at low cost, did we obtain a ma- 
 terial capable of causing the revolution in the paper in- 
 dustry mentioned in the preface. As is the case with all 
 important discoveries, it took considerable time before the 
 experiments in the separation of vegetable fibre, dating 
 since the year 1840, led to the practical results by which 
 we have profited in so great a measure. By different ways, 
 successively and repeatedly improving the method of their 
 
8 THE MANUFACTURE OF CELLULOSE. 
 
 predecessors, a number of men succeeded in manufactur- 
 ing cellulose, and later on several large groups have be- 
 come crystalized according to the method of manufacture. 
 The thickness of fibre, strength, purity, elasticity and 
 bleaching capacity of the different cellulose thus produced 
 are to the advantage of the paper manufacturer, because 
 the demands are endlessly varying and the manufacturer 
 is in a position to select the different suitable sorts or to 
 work in several at the same time. 
 
 Notwithstanding the different methods and the differ- 
 ence in the details of the manufacture a conclusion as to 
 the best method of development has not yet been reached, 
 for very lately, electricity has entered the arena, to assist 
 in dissolving the incrusting constituents of the fibre. 
 
 The evolution of the very important invention of the 
 production of cellulose may be best illustrated by the fol- 
 lowing chronological list of the names of those men who 
 are either inventors of new methods or who merit notice 
 by improvements and the introduction of practical appa- 
 ratus, etc. 
 
 Year. Name. 
 
 1840 Paven. 
 
 1852 Coupler & Miellier. 
 
 1853 Watt & Burg-ess. 
 1855 Juillon. 
 
 1857 Houghton. 
 1861 Barre & Blondel. 
 1864 Bachet&Machard. 
 1866 Tilghmann. 
 
 1866 Ekman. 
 
 1867 Fry. 
 
 1870 Dresel. 
 
 1871 R. Mitscherlich. 
 
 1872 Ungerer. 
 
 1872 Ritter-Kellner. 
 
 1873 Roemer (in Net- 
 
 tingsdorf). 
 Orioli. 
 
 1880 Cross. 
 
 1881 Francke. 
 
 1882 Pictet. 
 
 1882 Graham. 
 
 1882 Flodquist. 
 
 1883 Blitz. 
 
 1883 Dahl. 
 1885 Kellner. 
 1890 Lifschutz. 
 
 Dissolving Agent. 
 
 Nitric acid. 
 
 Soda. 
 
 Alkalies. 
 
 Alkal ne bases. 
 
 Alkalies. 
 
 Aquous acids. 
 
 Hydrochloric acid. 
 
 Sulphite of lime dis- 
 solved in sulphurous 
 acid. 
 
 Sulphite of magnesia. 
 
 Water of high temper- 
 ature. 
 
 Soda. 
 
 Sulphurous acid. 
 
 Soda. 
 
 Sulphurous acid. 
 
 Nitric acid cold method. 
 
 Aqua regia. 
 
 Water with neutral sul- 
 phites. 
 
 Sulphurous acid. 
 
 Aquous solution of sul- 
 phur dioxide. 
 
 Sulphurous acid. 
 
 Sulphurous acid. 
 
 Alkal' es and sulphites. 
 
 (Amonium "Vanadinate). 
 
 Sulphate. 
 
 Electricity. 
 
 Nitro-sulphuric acid. 
 
 Method. 
 Acid process. 
 Soda process. 
 Soda process. 
 Soda process. 
 Soda process. 
 Acid process. 
 Acid process. 
 
 Sulphite process. 
 
 Soda process. 
 Sulphite process. 
 Soda process. 
 Sulphite process. 
 Acid process. 
 
 Acid process. 
 
 Sulphite process. 
 Sulphite process. 
 
 Sulphite, process. 
 Sulphite process. 
 Sulphite process. 
 
 Sulphite process. 
 Soda process. 
 Electric process. 
 Acid process. 
 
THE MANUFACTURE OP CELLULOSE. 9 
 
 There ;irc thus four processes: 1. The acid process. 2. 
 The soda process. 3. The sulphite process. 4. The elec- 
 tric process. Of these, the first, the acid process is no 
 Longer of importance in practice; it has now hut theoretic 
 and historic value. Besides the above mentioned, nitric 
 acid, nitro-muriatic acid, muriatic acid and sulphuric acid 
 were also used by some for the purpose of cellulose man- 
 ufacture, hut on account of many disadvantages were dis- 
 carded when the other methods proved more practical. 
 These three other methods, viewed from a general stand- 
 point, have one point in common. The cellulose is pro- 
 duced by treating the disintegrated wood with a solution 
 under pressure in a boiler and by washing and milling. 
 The details naturally vary, some manipulations, however, 
 especially at the start and finish are the same with all 
 methods. In this treatise, which is to serve in practice 
 first of all, the methods shall, therefore, not he gone over 
 one by one, as then much would have to he repeated; but 
 the whole of the cellulose manufacture will be described 
 in its successive phases, while the variations of the differ- 
 ent systems will be considered as points of difference arise. 
 
 Efforts have been made to produce cellulose from every 
 kind of cheaply obtainable wood species, leaved wood as 
 well as pine, hut in general the wood of the pine and fir 
 have given the longest and best fibre, though even in pine 
 this varies according to the location of the tree, and its 
 quicker or slower growth. Pine wood cells measure up to 
 9 mm. the longest way, while the leaved woods have a 
 much shorter fibre. The quality of cellulose yielded by 
 different woods may he seen in the following table by E. B. 
 Griffin and A. I). Little. 
 
 
 
 
 
 u h 
 
 
 to 
 
 m 
 
 
 
 
 0, £ 
 
 fcx! 
 
 
 >. <D 4J 
 
 Spe 
 
 cie 
 
 of Wood. 
 
 E c 
 
 - Qj — * 
 MO 
 
 '»■" g 
 
 - 3t3 
 
 J3 
 
 to ■>-' 
 
 !■§ 
 1.5 
 
 
 
 
 O £fi 
 
 2 oc 
 
 M 
 
 u 'n 
 
 Ss^ 
 
 
 
 
 oi 
 
 aj to ™ 
 
 'T" 
 
 2 c 
 
 £ 10 oC 
 
 
 
 
 J 
 
 e 
 
 N 
 
 c ■« 
 
 £ 
 
 Fir 
 
 
 
 2.81 
 4.80 
 
 2.73 
 1.85 
 
 66.32 
 80.35 
 
 28.14 
 13.00 
 
 50.75 
 
 Poplar 
 
 
 
 55.18 
 
 Birch 
 
 
 
 2.14 
 
 0.93 
 
 82.99 
 
 13.94 
 
 42.80 
 
 Yellow 
 
 
 1.88 
 
 0.97 
 
 82.36 
 
 14.79 
 
 53.80 
 
10 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 In regard to soda-cellulose the following table is inter- 
 esting. It gives the yield in cellulose from one volumeter 
 each of the different kinds of wood; it also gives the loss 
 by barking and cleaning. 
 
 -s s So „- 
 
 ■i b[ * r I s ! 
 
 2? s - "n 5 H 
 
 ^ t: .5 ^ f sh ^ 
 
 Species of Wood ~ « "3 mo ol?! 2 S "3 15 
 
 Recently Cut. > g & §S &■>■*& .5>U .go 
 
 Per 
 
 Kilo. Kilo. Kilo. Kilo. Kilo, cent 
 
 Pine 617.5 80 230 307.5 108.2 35 
 
 Spruce Fir 566 136 191.7 238.3 88.2 37 
 
 Scotch or White-fir... 697.5 170 252.2 275.3 105.7 38 
 
 Black Fir 707.5 147 285.6 274.9 89 34 
 
 Larch 597.5 90 160.37 347.13 116.8 33 
 
 Leg- Fir, dwarf pine... 449.3 55.1 124.8 269.4 99.81 37 
 
 Red Beech 865 70 327.54 467.46 139.8 30 
 
 White Birch 623.5 111.5 215.04 296.96 85.6 29 
 
 Asp 695 135 227.36 332.64 108.42 32 
 
 Poplar 650 175 226.5 248.5 88.14 35 
 
 Mountain Ash 725.5 131.5 269.67 324.33 100.6 31 
 
 Wild Service Tree 756.5 166.5 224.2 365.8 103.96 28 
 
 Border Willow • 572.5 80.5 241 251 85.7 34 
 
 Brittle Willow 583.5 111 181.4 291.1 104.8 36 
 
 Ash ■ 593.5 91 100.1 402.4 103.95 26 
 
 Alder 516.5 97.5 181 238 82.3 34 
 
 The above analysis shows that the yield in cellulose, ex- 
 pressed in percentage, does not vary much in the different 
 kinds of wood, though in general the pines give a some- 
 what larger amount of cellulose. Besides this the quality 
 of cellulose from pinesi is better, and as this wood is more 
 plentiful, the price is lower. As a result these kinds are 
 principally used. 
 
 The Scotch pine, though abundant, in some countries 
 and cheap, is on account of its large content of resin, sel- 
 dom used for cellulose, although under certain conditions 
 it yields a good product as Herr Dresel in Dalbke has 
 proved by his method. 
 
 Since the manufacture of cellulose and wood pulp has 
 reached such immense proportions speedy extirpation of 
 our forests by this industry and the inevitable conse- 
 quences of irrational forestry are suggested. Fortunately 
 
THE MANUFACTURE OF CELLULOSE. 11 
 
 a satisfactory answer to this can be given by the following 
 figures and explanations, which are taken from a lecture 
 by Dr. Frank as published in the Papier Zeitnng: 
 
 ■'In Germany there at present about sixty cellulose 
 factories, which work into wood fibre stuff about 2,000 
 festmeters, equal to 3,000 volumeters of wood per day, 
 (bus turning oyer thirty millions of marks per annum, of 
 which amount about ten millions will flow into the treas- 
 ury of the forest administration. This daily quantity of 
 
 3.000 volumeters requires the cutting of an area of six to 
 eight hectars of forest. According to information from 
 a competent party in Germany, in sixty years rotation the 
 average yearly yield in solid wood may be put for fir at 
 
 3.1 festmeters, for pine 4.9 fm., so that the yearly need of 
 our cellulose factories to the amount of 600,000 festmeters 
 the regular yield of a forest area of from 150,000 to 160,- 
 000 had is fully required. Pine being especially suitable for 
 wood fibre the prices id' this wood, which formerly on ac- 
 count of its poor qualifications for timber were far below 
 those of fir, have rapidly risen and the far-seeing Prussian 
 forest administration has already by increased cultivation 
 so well met this condition that at present 274,416 hectar 
 of pine forest in the possession of the State contain 8,308 
 bectar of 100-year stock. 17,727 hectar of 81-100-year 
 stock, 30,752 hectar of 61-80-year stock, 4S,413 hectar of 
 41-60-year stock, (i."),iil(i hectar of 21-40-year stock, 92,075 
 hectar of 1-20-year stock. To this increased pine culture, 
 in which also the forests in private possession will follow 
 suit, is the more important; as in the manufacture of wood 
 fibre we must reckon with the competition of other coun- 
 tries, which get the wood material much cheaper than we 
 do; in Europe there are especially Sweden and Baltic 
 provinces of Prussia, both very favorably situated conn- 
 trie- for export, and in America, Canada now enters into 
 competition with equal facilities. 
 
 A festmeter of pine wood weighing about 450 kilos. 
 above T festmeter correspond to about 3,150 kilos of pure 
 wood pulp and as (i festmeters pine wood yield about 1,000 
 kilos of pure wood fibre, the annual yield per year of the 
 pine would correspond to 1,166 kilos of cellulose pro- 
 duced thereof per hectar. 
 
 Fach individual cellulose concern must procure the most 
 suitable pulp wood at the lowest shipping expense. In 
 
12 THE MANUFACTURE OF CELLULOSE. 
 
 this connection it is to be considered that freshly cut 
 wood is the easiest worked, and produces the best cellu- 
 lose, but it weighs heavier and by increase of freight be- 
 comes dearer. It is therefore to be recommended that 
 when the logs first enter the factory they be assorted, sep- 
 arating the older and dryer ones. Of the dry, which were 
 lying in the woods a considerable time, special care is to 
 be taken to throw out those rotten in the core, because 
 such partially reddened wood produces but inferior cellu- 
 lose. In any case, when cutting the logs later on, the various 
 ]}ieces, exhibiting a change in the white wood color, should 
 be laid aside, to be used as kindling wood, or when enougb 
 has accumulated to be worked into third quality cellulose. 
 
 WOOD WOKKING. 
 
 The wood used in cellulose manufacture must first be 
 barked, and such is done either by hand, with the knife, or 
 by a barking machine, also by both methods successively. 
 
 When heavier wood has to be worked, and when the 
 barking is to be done by machine, it becomes necessary to 
 cut. the logs with a log saw, swinging like a pendulum, in- 
 to pieces of about 60 cm. long. In figures 1 and 2 such 
 practical saw is illustrated. A wooden frame, the length 
 of which depend on the height of the workshop, is on its 
 upper end provided with two wooden pins, resting in two 
 hanger boxes BB. In the lower end of the swinging 
 frame is rested a short shaft, to which on the left is fast- 
 ened the circular saw-blade of 860 mm. diameter, which by 
 transmission receives a velocity of about 900 revolutions 
 per minute. In front and at the side of the circular saw 
 is placed a wooden frame, provided with sliding rollers, up- 
 on which the log is laid and easily pushed against the saw- 
 blade. 
 
 With his right hand the operative presses the toothed 
 lever against the log, to hold it in position and with the 
 left hand with one grasp he pulls the rotating saw against 
 the log, cutting through it rapidly. Its own weight at 
 once brings the frame back to the vertical position, the 
 helper again pushes the log ahead and the cutting is re- 
 peated. In this operation it can be easily noticed on the 
 cut edges, whether the wood is part good or part rotten, 
 and the bad pieces are thrown out, as stated above. With 
 great rapidity now follows the use of the barking ma- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 13 
 
 chine, of which figures 3, 4 and 5 show a practical con- 
 struction. 
 
 Encased in a cast iron frame the barking machine is 
 
 e T? 
 
 BLOCK SAW. 
 
 set upon a vertical shaft, the principal part, a circular ta- 
 ttle or wheel of 830 mm. diameter, revolving 330 times 
 per minute. This wheel has near the periphery five slits. 
 
14 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 as shown in figure 4, through which from below, diagon- 
 ally movable knives are put, which are raised above the 
 table but a few mm., and while rapidly revolving peel off 
 
 Fitf, 3 
 
 BARKING MACHINE. 
 
 in long slices the bark off the wooden block c, which is 
 pressed against the knives by the lever 9. As the block is 
 
THE MANUFACTURE OF CELLULOSE. 
 
 lfi 
 
 also kept turning by a toothed wheel;, the harking is done 
 equally over the whole circumference. If now all blocks 
 wvre exactly cylindrical, the work in the manner described 
 would suffice, but some pieces are crooked and often have 
 humps and hollows, and it is also necessary that not only 
 the brown bark, but also the underlying white bast be re- 
 moved in order to produce a good cellulose. Consequently 
 after cleaning with the axe or knife on the ordinary work 
 I tench must follow. Exact experiment by the author with 
 wood of estimated weight and nearly equal bulk have 
 shown the following results. When the wood is barked by 
 machine and after cleaning by hand, 10 festmeters cost 
 about 5.5 marks for labor, while 10 marks have to be ex- 
 
 FIG. 5. BARKING MACHINE. 
 
 pended when barked by hand only. In the latter case it 
 is True the loss by barking is about 1.4 per cent less, never- 
 theless the use of the machine is to be recommended, as 
 thus much time and money are saved. 
 
 In place of the above described barking-machine a so- 
 called duplex may be used, on which two blocks can be 
 worked at the same time, or also one with a wheel rotating 
 vertically. The barking shop is generally located on the 
 ground floor of the factory. By an elevator the barked 
 
16 
 
 THE MANUFACTURE OF CEUUULOSE. 
 
 blocks are then transported to a higher floor to be still 
 more diminuted. Some manufacturers at this stage have 
 the knots bored out, because as these do not become soft 
 in boiling they do not yield cellulose, and further the fibre- 
 ous parts, laying next to the knots as a rule remain hard, 
 or at least yellow. Even by boring them out, they cannot 
 be removed entirely, so that it seems advisable not to sort 
 them out until later. The diminution of the wood, neces- 
 sary for the more thorough action of the leach in the 
 subsequent boiling may now either be done with circular 
 saws which cut the blocks into slices of 25 to 30 mm. 
 thickness, or by chip — or cut — machines. In the former 
 case according to the capacity of the plant a larger number 
 of ordinary single circular saws or those with several saw- 
 blades in a row are used as a rule. Because the labor of 
 feeding has to be done by hand and accidents to those em- 
 
 FTG. fi. 
 
 ployed therein may easily happen, it is necessary to pro- 
 vide all possible safety arrangements and especially caps 
 over saws. In order that the operatives, who mostly do 
 the sawing by contract, do not make the slices larger than 
 desired, it is advisable to fasten to the table in front of the 
 saw a small angle iron, which stands sideways about 25 to 
 30 mm. off the saw-blade and answers as a guide. The 
 shorter the block becomes the greater the danger for the 
 operative, if he presses the block against the saw with 
 naked hand. If the operative uses a short piece of wood 
 with a handle on one and several steel points in the other 
 end, which he pushes every time in the head of the block 
 to be cut, he can thus easily guide the block and the dan- 
 ger of possible injury is almost excluded, 
 
 In using circular saws it. is very important to take care 
 that the saw blades are thin, the best possible, and that the 
 
THE MANUFACTURE OF CELLULOSE. 17 
 
 set of the points of the teeth of the saw (the spreading) to 
 the right or left is just so much, that the saw does not 
 get clogged in cutting. The waste of sawdust, even with 
 observance of the precaution mentioned, is very large in 
 proportion, and may increase if these directions are not 
 followed. When slices of 35 to 30 mm. thickness are to be 
 cut. in every log of 1 m. length at least 33 cuts have to lie 
 made, and when for each of them hut 4 mm. loss is admit- 
 ted, the result is 132 mm. per thousand, or 13 per cent. 
 Though this waste appears very clean, it yet contains many 
 small particles of knots, yielding brown spots in the cellu- 
 lose. If too high demands are not made on the product, ihe 
 dust may be filled in the boiler together with the slices, 
 the whole or part of it mixed, hut care should he taken 
 that it is placed in about the middle of the total charge of 
 the hoiler so that in discharging the leach it would not 
 clog the valves, or when swimming on top it would not 
 spoil the whole operation. It would certainly be better to 
 leave out the dust entirely, or at least to use it together 
 with low grade wood for a cheaper quality. At this point 
 may he mentioned, that lately the shavings from barking, 
 especially such not charged with brown hark, are boiled 
 into cheap cellulose by some manufacturers. Because, in 
 proportion to their weight, not many can he filled into the 
 boiler, they are cut by a chopping machine into short frag- 
 ments, which often being charged into the boiler are trod- 
 den down by a laborer, so that the yield in cellulose in 
 each operation is but 10 to 15 per cent, less than in an 
 operation with good wood. In this manner the working 
 of shavings is made profitable, while previously they were 
 mostly used as fuel. Mixed with sawdust or waste from 
 pulp milling, they may also be worked into lesser grades 
 of wood fibre. It may also he mentioned that with the 
 above described methods of cutting wood, the knots exist- 
 ing in the different slices are, as a rule, not sorted out be- 
 fore boiling, because the smaller ones could not all be 
 picked out by any means, and sorting after boiling would 
 still lie necessary. After the wood is softened by boiling, 
 every knot can lie detected with the finger and easily 
 picked out. 
 
 When a chipping machine is used in reducing the wood 
 to be boiled the disadvantage of great loss of saw dust is 
 eliminated, because the previous harked wood is hewn off 
 
IS THE MANUFACTURE OF CELLULOSE. 
 
 the head in somewhat oblique direction in fragments, meas- 
 uring about 30 mm. In consequence of the forcible bear- 
 ing away the particles also receive cracks in all possible 
 directions, thus becoming loosened and permitting the 
 leach to permeate them in the subsequent boiling. The 
 main part of such chipping machine is a heavy oast iron 
 wheel of 1,400 mm. diameter on a strong horizontal shaft. 
 To prevent springing a ring of forged iron, 50 mm. wide, 
 is fastened around it while warm. Near the circumfer- 
 ence one or two strong knives are fastened, each by nine 
 screws, which stand about 5 mm. off the wheel and which 
 move quite rapidly on a stationary support, over which the 
 wood to be cut is introduced. When lighter wood is 
 worked the previously hand-barked pole is fed to the 
 machine by two men, and must be turned about after each 
 cut. Another laborer shovels the chips upon the elevator, 
 which takes them to the upper lofts. The machine natur- 
 ally requires much power and because it continuously re- 
 ceives heavy shocks, it is best to place it on the ground 
 iloor, and as stated, to transfer the cut wood upwards. The 
 machine is capable of chipping in 12 hours about 35 cubic 
 meters of wood from the head of poles about 2^ m. long. 
 In some factories, however, the machine is placed in up- 
 per lofts; the wood is in short pieces, previously peeled on 
 the barking machine, and the blocks are put on an end- 
 less band and automatically led to the chipping machine. 
 The wood, reduced as described above, is moderately filled 
 into the boilers in cases where the factory does not work 
 prime cellulose. In most cases, however, it is first assort- 
 ed by a number of boys or girls. For this purpose it is 
 thrown upon a sifting table, where dirt and very small 
 chips fall through and every piece containing a knotty 
 part, is sorted out by hand. This method is quite expen- 
 sive, and in each case particular care should be taken in 
 calculating whether the cost of labor for sorting is recov- 
 ered by the production of a high grade and pure cellulose. 
 A later design of a chipping machine, described in the 
 Papier Zeitung, originates from geh. Commerzienrat 
 Albert Methammer and seems to be based on the prin- 
 ciple of pencil sharpening. By this method the wood is 
 not cut directly across the grain as in some machines, but 
 is sliced off in long chips. In this manner the machine 
 requires less power and has to suffer much less violent 
 
THE MANUFACTURE OF CELLULOSE. 
 
 19 
 
 shocks. The cutting away almost vertically on the long 
 axis of the wood is not desirable on account of the large 
 consumption of power. As a rule an angle of 45° is ac- 
 cepted as the most effective, for where the wood is cut at 
 that angle the cells are opened, and the wood inside is 
 crushed and loosened to such extent that the leach can 
 enter easier and quicker. Whether the knife, which does 
 the principal work, and which in this machine had to he 
 made thin, has worked well, is not known to the author. 
 
 FIGURE 7. 
 
 The entire construction can be learned from figures 7, 8, 
 9 and 10 and from the following description: 
 
 Fig. 7 presents the front view, fig. 8 the side view, with 
 part cut, fig. 9 the view from above (the plane), fig. 10 
 shows in enlarged scale the knife holder with knife. 
 
 The frame A, in which is the cranked driving shaft, de- 
 velopes upward into a stand A', the front face of which is 
 inclined. To the stand A' the adjustable guiding posts n 
 are fixed, along which a sled f can be moved up and down 
 
20 
 
 THE MANUFACTURE OP CELLULOSE. 
 
 The latter carries the knife a, with the frame d (fig. 10), 
 covering it at the edge. With the knife-sled f is con- 
 nected a cross beam 1, to which are connected the two 
 driving rods m, linked to the crank of the driving shaft B. 
 On the right and left of the shaft, outside of the hearing 
 boxes are the fly wheels D and Dl, one of which serves as 
 driving pulley. Alongside of this is the loose pulley D2. 
 It is at once evident that the sled f with the knife and the 
 cover-frame in one turn of the shaft B makes a lift along 
 the inclined face of the frame Al corresponding to double 
 the length of the eccentricity of the shaft crank. By using 
 
 FIGURE 8. 
 
 two connecting rods, cornering of the knife-sled f at the 
 adjustable leaders n is prevented. The log is fed upon a 
 table C in a direction oblique to the axis of the shaft B\, 
 but in level position, so that the line of the cut is inclined 
 to the long axis of the fibre, as well as to its perpendicular, 
 and thus the fibres are cut through in a doubly inclined 
 direction. 
 
 To obtain undamaged slices the knife has to be very thin, 
 and to give to the thin knife (fig. 9) sufficient resistance 
 and stiffness, it is fastened to the knife support f, not only 
 with its upper edge, but also with both sides with screws, 
 
THE MANUFACTURE OF CELLULOSE. 
 
 21 
 
 and the latter as well as the frame d, covering the upper 
 side of the knife, are for this purpose cut out in a semi- 
 circular form. 
 
 The knife, the edge of which is somewhat beveled, does 
 not cut against a stationary^ so called stock-knife, but en- 
 ters in its lowest position into a correspondingly wide slit 
 of the log support. The automatic advancing of the log is 
 secured by means of two pairs of rollers, upon one of which 
 lays the log, while the second pair of rollers (o) holds the 
 log in the proper position from above. 
 
 FIGURE 9. 
 
 The feed is broken during about one-quarter of the revo- 
 lution and is going on only when the knife has accomplish- 
 ed the upper part of the motion. In this manner it is pos- 
 sible to cut logs of a diameter equal to three-fourths of the 
 lift of the knife. This periodic feeding is secured by the 
 eccentric (g), which is fixed to the shaft B and upon which 
 runs a roller (h), borne in the arm (p) of an angle-lever 
 (pr), turning about the pin (q). The second arm (r) of this 
 lever is, by the car (s), which is provided with a universal 
 joint, connected with one arm (t) of the angle-lever (ttl); 
 the second arm (tl), by the push-bar (si), also provided with 
 universal joint, is likewise connected with the lever (u). 
 
22 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 When the pulley (h) is lifted by eccentric (g) the bar 
 (si) (fig. 8 and 9) is pushed to the right and hence the two 
 levers (mil), which are connected together by the push-car 
 (y), also stick to the right with their upper ends. On 
 the upper ends of these levers are friction latches (wwl), 
 provided with rollers, which trail upon the edged disks (xxl) 
 in a way that, with the above mentioned swinging to the 
 right of the lever ends the disks (xxl) are carried along. 
 With the swinging to the left of the lever ends, the latches 
 
 FIGURE 10. 
 
 (wwl) slide back over the final rollers. The levers (uul) 
 turn loosely on the spindles of the disks (xxl). The spindles 
 bear the rollers, which support. 1 the log from below, so that 
 with every turn of the disks (xxl) this pair of rollers will al- 
 so turn, and thus the log is correspondingly pushed forward. 
 The end of the bar (si) at its connection with the 
 lever (u) slides in a groove by which means the amount of 
 feed can be regulated. The pulley (h) running on the ec- 
 centric (g) follows the latter when the number of revolu- 
 tions is low, but when 80 to 90 per minute the molecular 
 
THE MANUFACTURE OF CELLULOSE. 23 
 
 forces act hinderingly, and the pulley does not follow the 
 delivery of the eccentric curve with sufficient quickness. 
 To avoid the shocks which would result, a spiral spring (i) 
 is arranged, which with one end is fastened to the angle- 
 lever (pr), and with the other to a spiral wheel (y), which 
 is in action with a second spiral (2), put in rotation by 
 means of a key, so that the spiral spring can be suitably ad- 
 justed to give the necessary acceleration to the pulley. A 
 small roller (r), borne in one end of a toothed bar, serves 
 to hold down the log before the knife. 
 
 In conclusion the author has computed a table from 
 practical observations, to ascertain whether it is of more 
 advantage in the manufacture of cellulose to use light or 
 heavy logs. These values refer to the first mentioned case, 
 where the wood is cut into slices by the circular saw. 
 
 
 
 
 
 
 
 . 
 
 
 to 
 
 
 w to'ffi 
 
 <U to 
 
 n o 
 c s- 
 
 CD to 
 
 c£ 
 
 £e 
 !« 
 
 3 a> 
 
 5.5 
 
 3 
 o d, xfi 
 
 to 
 
 h 
 
 to <u 
 
 3 3^ 
 
 O to "o 
 
 O °r 
 
 cii 
 
 C ai 
 
 •2? 
 
 Face of Cut per 
 1 Volumeter 
 in Sq. M.. 
 
 G 
 O 
 
 3S 
 H G 
 
 -a aj 
 3 w 
 0_ 
 
 "- 1 r« t0' 
 
 Time per 100 Cubi 
 Meters and 2 Saw 
 Work Days of 10 
 
 -t-> tO 
 
 || 
 
 oh 
 
 AX 
 
 s- E 
 
 M <u '" 
 
 3 S £ 
 
 5m E 
 
 Is 
 
 Em 
 
 
 ° r i 
 Si aj 
 
 to ™ 
 — o* 
 
 0«2 
 
 OJ CD 
 
 D,bO 
 a; s-, 
 
 % ad 3 
 
 <" in 
 
 E +*« 
 
 C qj 
 
 h§.5 
 
 9 
 
 121 
 
 28.26 
 
 34.2 
 
 242 
 
 3936 
 
 63.6 
 
 25.00 
 
 1.5 
 
 98 
 
 8.17 
 
 10 
 
 100 
 
 31.4 
 
 31.4 
 
 200 
 
 3200 
 
 78.5 
 
 25.12 
 
 1.85 
 
 59 
 
 4.91 
 
 15 
 
 44 
 
 47.1 
 
 20.7 
 
 88 
 
 1408 
 
 176.5 
 
 24.85 
 
 2.2 
 
 51 
 
 4.3 
 
 20 
 
 25 
 
 62.8 
 
 15.7 
 
 50 
 
 800 
 
 314.0 
 
 25.12 
 
 3.6 
 
 48 
 
 4 
 
 25 
 
 16 
 
 78.5 
 
 12.5 
 
 32 
 
 512 
 
 489.8 
 
 25.07 
 
 8.8 
 
 75 
 
 6.25 
 
 28 
 
 14 
 
 87.9 
 
 12.3 
 
 28 
 
 470 
 
 615.4 
 
 28.9 
 
 13.6 
 
 94 
 
 7.8 
 
 30 
 
 11 
 
 94.2 
 
 10.4 
 
 22 
 
 352 
 
 706.5 
 
 24.86 
 
 18.5 
 
 112 
 
 9.3 
 
 34 
 
 9 
 
 106.7 
 
 9.6 
 
 18 
 
 269 
 
 907.4 
 
 22.4 
 
 34.0 
 
 152 
 
 12.7 
 
 This computation is not quite carried in practice, as for 
 instance for woods of 10 m. thickness, 10x10 100 pieces are 
 set in 1 square meter. With close observation one may 
 learn from this table that with thinner wood, the surface 
 to be barked, and consequently the waste is the largest; 
 therefore it would be of advantage to work only very thick 
 trees, if prices were the same. The cross section really to 
 be cut in one volumeter of wood is almost equal in thick 
 and thin wood, namely, about 25 sq. m., whereas the work- 
 ing time necessary to cut one volumeter of wood of light, 
 medium and heavy quality into slices of 30 mm. thickness 
 differs greatly. It is the great number of the necessary 
 
24 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 cuts and the loss of time between the single cut in thin 
 wood which makes its use unprofitable; while in very heavy- 
 wood the saw meets too much resistance, becomes clogged, 
 goes slower and takes considerably more time to do the 
 same work. But as time is money and very heavy logs 
 have a higher timber value, their use is not recommended. 
 The table shows plainly that it is the most profitable to 
 buy medium heavy wood of about 20 cm. diameter. As a 
 consequence of the continually increasing competition and 
 
 FIGURE 11. 
 
 the increased demands of the wood fibre consumers many 
 changes have taken place in recent years, in the working 
 of the wood, which, without regard to the different patent 
 processes in the manufacture of cellulose have found ad- 
 mittance uniformly in the factories of the different sys- 
 tems, as it is now the main object to save as much as pos- 
 sible in power and labor, as well as to manufacture a pro- 
 duct as pure as possible. A plant already introduced in a 
 great number of factories by the foundry and machine 
 works (formerly Goetjes <fe Schulze in Bautzen, fulfills 
 
THE MANUFACTURE OF CELLULOSE. 
 
 2fi 
 
 these conditions, and the machinery previously used has 
 beerj connected with the new and shaped into a practical 
 whole. In the process the logs are cut by a log-saw in 
 blocks of 1 m. or less as already described. These' are 
 barked by a single or double barking machine and, when 
 heavy wood is used they are also split by a splitting ma- 
 chine, such as are in use in wood pulp factories. This 
 splitting is for the purpose of facilitating the work of the 
 chipping machine, because the hewing of the chips off 
 heavy logs requires decidedly more power than off a thin 
 one. The chipping machine, as already mentioned, is at 
 
 , __ 
 
 CL 
 
 J3 
 
 FIGURE 12. 
 
 present usually built with two knives and the feeding of 
 the wood is not as originally practiced, oblique to the 
 horizontal and vertical to the ground section of knife 
 blades, but oblique to both directions, as shown in figures 
 11 and 12. 
 
 Thus the cutting of the chips is done along the long axis 
 of the wood, which is naturally easier, than hewing of the 
 head wood. The feed arrangement is obtained by a semi- 
 circular gutter,' which is cast to the frame and in which the 
 log-pieces are placed, being fed to the knives by their own 
 weiffht. As the knives are 500 mm. long and 150 mm. 
 
2& 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 wide as a rule, two guiding gutters alongside each other are 
 provided, so that two logs may be cut at the same time. 
 When care is taken that the knives are always sharp, which 
 necessitates a change ever}'' two hours, such chip machine 
 can in twelve hours out as much wood as is needed for a 
 daily production of 6,500 kgr. of dry cellulose. This re- 
 peated changing of the knives is further to be recommend- 
 ed, because of the fact that they get warm in the working. 
 
 FIGURE 13. 
 
 The chips hewn off then fall below the machine directly 
 upon a wide band, moving slowly along, and carry the wood 
 to the so-called breaker. On the way there the principal 
 and largest knots are sorted out. Contrary to Professor 
 Mitscherlich, who has recommended the cutting into slices, 
 Dr. Karl Kellner has found from the beginning that the 
 most thorough splitting of the wood fragments is of ad-' 
 vantage in permitting the entrance of the leach, and there- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 27 
 
 fore was not satisfied with the effect of the chipping ma- 
 chine alone, hut besides uses the breaker, which is con- 
 structed after the common coffee mill, as shown in fig. 13. 
 The chipped wood, which in consequence of the force and 
 strain of the chipping is already full of minute cracks, is 
 fed by the elevator to the funnel, into the casing (g), which 
 is conical in shape, widening towards the bottom. The 
 wall of the casing is provided with sharp teeth and within 
 a smaller cone K, also set with teeth, is revolving rapidly. 
 The distance between the stationary and movable parts is 
 so proportioned that the chips of wood are considerably re- 
 
 FIGURE 14. 
 
 duced in size, while the harder knots fall through unbroken. 
 In place of this breaker the centrifugal machine has been 
 lately used with success. It is claimed to work more ad- 
 vantageously because it does not tear the fragments so 
 much, and renders easier the separation of the knots and 
 knotty parts from the sappier wood. A cross section of 
 the characteristic parts is shown in fig. 14, and in fig. 15 
 the front view. 
 
 Inside of a. casing, on the front wall round pins of forged 
 iron are set in two concentric rings, between which two 
 
28 THE MANUFACTURE OP CELLULOSE. 
 
 smaller rings of pins are rapidly moving. These latter 
 mentioned pins are set in a round disk, which is wedged 
 on a horizontal shaft. The elevator • throws the chips of 
 
 FIGURE 15. 
 
 wood into the flat pipe (a) cast to the front wall, from 
 where they enter immediately over the shaft into the 
 middle of the apparatus, get caught by the pins of the 
 
 W/////////////////////////?////////////////// A 
 
 FIGURE 16. 
 
 rapidly rotating disk (about 1,000 revolutions per minute), 
 thrown around, crushed and separated from the knots. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 29 
 
 Through an opening in the case the wood then falls upon 
 an elevator band below, which carries it further to the ro- 
 tating apparatus. 
 
 For a quantity of 6,500 kilos of dry cellulose supposed 
 to be worked per day, this machine consists of two conical 
 drums of 6 to 7 m. long and about 2 m. in diameter, the 
 constructions of which is shown in fig. 16 and 17. The 
 drums, mack' of wooden rings, rest in the front, rear and 
 eventually in the middle upon two driving rollers each, 
 which rotate rapidly, the large drums making about 12 
 revolutions per minute. The inside of the wooden frame 
 work is lined with perforated sheets, thus forming a 
 smooth, large funnel, into the smaller end of which the 
 fine wood is carried by the elevator. By rotation of the 
 cone the wood is carried up part of the circumference, and 
 
 FIGURE 17. 
 
 thus slides along the smooth wall towards the wider end 
 of the funnel, or falls through the numerous openings 
 under the drum. Because it must perform at the same 
 time a cleaning, as well as a sorting of the pieces according 
 to size, and possibly also a separation of the knots, the fore- 
 most smaller part of the drum lining has fine holes of 
 about 6 mm diameter, a second part has larger openings and 
 the third part at the wide of the funnel'lias the normal 
 openings, which answer the size of the good pieces to be 
 worked. Below the first and second department are 
 boxes closed by doors, in which the sifted material accumu- 
 lates. This consists in No. 1 of dust, splinters, knotty 
 particles and fine black knots and is either used in the fac- 
 tory for kindling, or sold for other purposes; No. 2 con- 
 
30 THE MANUFACTURE OF CELLULOSE. 
 
 tains medium sized pieces, mixed with, some knotty parts 
 and when enough has accumulated, it is separately worked 
 into second quality ware. The good wood from No. 3 falls 
 upon a band about 1 m. wide, which is at a right angle to 
 the drum, and carries its load slowly along, serving as a 
 table, at both sides of which girls are standing, who sort 
 out all pieces, which still contain knots. The main part 
 of knots will be larger than the opening for the good wood 
 and at the wider end of the funnel drops into a basket. The 
 contents of this basket naturally is again gone over and 
 larger, but clean pieces of wood, are sorted out to be fur- 
 ther worked. Because the use of elevators saves much 
 hand labor, one or more other elevators now expedite the 
 wood to a floor above the boilers into boxes., the capacity 
 of which corresponds to the boilers below. 
 
 LEACHES AND LEACHEMAKING; THE SODA PROCESS. 
 
 A.S the name suggests, soda is used in the soda process, 
 as leach in boiling. Originally this was in the form of 
 carbonate of soda, made caustic by adding lime, in order 
 to dissolve the incrusting constituents of the wood fibre 
 and to separate them from the pure fibre. In itself the 
 soda does not make the solution effective, but water must 
 be present and a high temperature must be employed. The 
 hot steam alone renders some of the incrusting constit- 
 uents soluble, and thus other products are formed, also 
 acids, which have dissolving qualities, but would have an 
 injurious influence on the fibre itself, were it not for the 
 fact that the presence of the soda neutralizes them while 
 the process of boiling is still going on. This depends 
 principally on the proper strength of the leach and main- 
 taining the necessary temperature (corresponding to the 
 pressure of the steam in atmosphere) also the length of 
 time for the process of boiling in proportion to the quan- 
 tity of the wood and its quality. It is quite natural that 
 the most diverse statements were made about this before 
 ■practical experience has established proportional values. 
 Professor Hager wrote in this regard the following: "In 
 1869 a tension of 4, 5 atmospheres (150° C) was consid- 
 ered sufficient by Keegan, while Lee in 1870 went up as 
 high as 11 atmospheres (210° C) — Ungerer in 1872 has as- 
 serted that a pressure of from 3 to 4 atmospheres (134°- 
 144° C) for leaved wood and from 5 to G atmospheres 
 
THE MANUFACTURE OF CELLULOSE. 31 
 
 (152° -159°) for pine wood answers the purpose, while 
 Kosenham in 1878 again stated that 10 atmospheres (180° 
 C) was correct. The statements by Urgerer seem to fit 
 the purpose best. However an account of the great risks, 
 presented by the high tension in boilers of such immense 
 dimensions, the pressure of 10 atmospheres (180° C boil- 
 ing temperature) should not be exceeded. In similar man- 
 ner, the quantities of soda, employed, and the strength of 
 the leaches deviate. According to the patent of Wott & 
 Burgess, the leach is made 12° B strong, of which so much 
 is taken that to 100 parts of wood, considered dry, 21 parts 
 of soda of 60$ purity are used. Sinclair has used 25 parts 
 of soda for 100 parts of wood, in a solution of 140° B. Ac- 
 cording to Ungerer, and employing his system a leach will 
 do, of which 4-5$ of caustic soda of 60$ purity is used with 
 leaved wood and 6-8$ to pine wood. Much less varying 
 are the statements about the time of boiling, which as a 
 rule is stated at from 5 to 6 hours for one operation." 
 
 These reports by Professor Hager, in conformity with 
 communications to the author, are to be corrected by the 
 statement that a pressure of 4 1-2 atmospheres is by no 
 means sufficient in the production of soda-cellulose; and 
 on the other hand, that until 1870 Lee has not been em- 
 ployed in the task of making wood fibre, and also that up 
 to 1872 Ungerer had not yet boiled cellulose. Besides 
 the latter had not employed 5 to 6, but 8 to 10 atmos- 
 pheres of pressure. It is mentioned conclusively that 
 lingers process has not proved so well in practice, as was 
 expected. The author is not personallv able to render 
 judgment in this; theoretically the process is well consid- 
 ered. The same writer further makes remarks about the 
 nature and solubility of the organic constituents of wood, 
 which are very interesting and by which is shown the suc- 
 cessive work of the' leach. He says: "The organic con- 
 stituents of the wood belong to several groups, as some 
 of them are soluble in water and consequently can be re- 
 moved from the wood by treating with water, while others 
 are insoluble in water. To the former belong gum, veg- 
 etable albumen, tannins, coloring matter, etc., to the latter 
 belongs the resins, balsams, etc. Lastly there is the in- 
 crusting matter or the lignin, which has been deposited 
 in and upon the membranes of the cells and vessels and 
 which is consequently most closely combined with the 
 
32 THE MANUFACTURE OF CELLULOSE. 
 
 cellulose. A wood fibre may therefore be conceived 
 as built up with, the cellulose as the elementary substance, 
 penetrated with lignin, next with a covering layer of resins, 
 etc., insoluble in water and finally a third layer, which 
 mainly contains substances soluble in water. This com- 
 position justifies the conclusion that- every layer protects 
 more or less the one laying below, against the action of the 
 solvents, and that removing the layers in reversed order 
 must lay bare the cellulose. Now, as the outer* layer is 
 soluble in water, it is sufficient to treat the wood first with 
 water or steam of such temperature, that no change of the 
 lignin can take place. Because the resins dissolve in weak 
 leaches, the application of such removes the second layer, 
 while the lignm is treated with stronger leaches at high- 
 er temperatures. Upon this principle, Ungerer in Vienna 
 has worked out a process of boiling, which must be con- 
 sidered the most perfect, because it treats the wood in suc- 
 cession with steam and leaches, the concentration and tem- 
 perature of which are continuously being raised, whereby 
 it at the same time the leach is worked to exhaustion and 
 excellent fibres is produced." 
 
 This system shall be described more particularly in the 
 next chapter. Here we have next to do with the leach and 
 its preparation, which is very simple in the soda process, as 
 soda and the other chemicals are simply dissolved in a 
 tank, in which by means of a steam coil the liquid can be 
 heated and then so diluted that the desired degree of con- 
 centration is obtained. But as soda is expensive, and as 
 it. would be extravagant to let it run to waste together with 
 the spent leach the idea was conceived soon after soda- 
 cellulose manufacturing was introduced, to evaporate the 
 leach containing all the incrusting constituents of the 
 wood fibre, and thus to regenerate the soda, whereby at the 
 same time the otherwise inevitable contamination of the 
 waters was avoided. Naturally the soda is not recovered 
 pure, several combinations being formed, but it was dis- 
 covered that the same action results from the intermediate 
 product of the soda manufacture, the sulphate of soda as 
 from the carbonate of soda. Dahl in Danzig, discovered 
 this about 1883 and he first used a leach containing sul- 
 phate of soda, carbonate of soda, caustic soda and sulphide 
 of soda. The leach is prepared from sulphate of soda and 
 23-25$ of caustic lime, to which are added the salts re- 
 
THE MANUFACTURE OF CELLULOSE. 33 
 
 covered from former leaches. The spent leaches are con- 
 centrated by evaporation, strongly calcined and after all 
 gases are driven off, pulled out of the furnace in the form 
 of coke. The mass is then lixivated and the solution ob- 
 tained serves to make new leach. To obtain it free from 
 coal, the concentrated solution is heated in a furnace to 
 dark redness. , The resulting mass, assuming a reddish- 
 brown color in cooling, is easily soluble in water and has 
 about the following composition: 
 
 Sulphate of Sodium 16$ 
 
 Carbonate of Sodium 50$ 
 
 Caustic Soda (soda) 20$ 
 
 Sulphide of Sodium 10$ 
 
 Different other substances 4$ 
 
 This composition varies considerably according to the 
 wood treated, but the solving power of the leach is not 
 much influenced. These salts recovered from the leach 
 must be dissolved soon to avoid the action of the atmos- 
 phere. In the boiling and recovering, about 10 to 15$ of 
 the salts contained in the leach get lost, and must be re- 
 placed with sulphate of soda. From 85 to 90$ of the re- 
 covered salts and 15 to 16$ of sulphate of scdium, which 
 has been boiled with 20 to 23$ of caustic lime, yield a good 
 leach. The quantity of the sulphate of soda treated with 
 lime, and the quantity of lime itself vary with the esti- 
 mated loss of the salts. At a loss of 10$, 10 kilos of sul- 
 phate of sodium and 20 kilos of lime are necessary for every 
 90 kilos of the recovered salts. At a loss of 15$, for every 
 85 kilos of the salts, 15 kilos sulphate of sodium and 23 kilos 
 of lime have to be used; at a loss of 20$, for every 80 kilos 
 of the salts, 20 kilos of sulphate of sodium and 25 kilos of 
 lime. In general the resulting leach contains about 37# 
 of sulphate of sodium, 8$ of carbonate of sodium, 24$ of 
 caustic soda and 3$ of sulphite of sodium. From the 
 above it will be seen that the process described differs from 
 the older process of boiling with caustic soda in that in 
 preparing the leach, the caustic soda lost in boiling and re- 
 covering of the salts is replaced by sulphate of sodium, in- 
 stead of by caustic soda, and the quantity of the caustic 
 lime used is reduced from 45$ to from 20 to 23$. 
 
 As in other lines of manufacture, competition has com- 
 pelled economies, especially since sulphite-cellulose has 
 made its appearance. In the course of time they substi- 
 
■ 
 
 34 THE MANUFACTURE OF CELLULOSE. 
 
 tute the cheapest grades in the market for the expensive 
 sulphates 1 free from acid and iron, first used because iron 
 and free sulphuric acid could, according to the manner in 
 which the sulphate was employed in the different factories, 
 either be made harmless in the form of sulphate of iron 
 and sulphate of lime 1 by the caustic process, or when 
 worked with the stock for calcination in the fire. Several 
 works, fortunately situated in the neighborhood of dyna- 
 mite factories, went over to the use of the waste product 
 of these factories; the acid sulphate of sodium. This salt 
 being nothing else then sulphate of sodium with consid- 
 erable percentage of free sulphuric acid, which, as already 
 mentioned, can be removed by chemical process or even 
 made useful. In general, however, this utilization of the 
 acid sulphate in the manufacture of soda wood fibre is not 
 a characteristic modification of the process of Dahle, which 
 in the manufacture of soda-cellulose is now in general use. 
 According to Dr. Frank this utilization of sulphuric acid 
 can be done by adding chloride of sodium, consequently 
 is utilized as sulphate of sodium. In the customary pro- 
 cess of neutralizing with lime the sulphuric acid does but 
 add a ballast of sulphate of calcium (gypsum), therefore 
 neutralization with spent leach would be still better. 
 
 At this point, after concluding the chapter about the 
 soda leaches and previous to the description of the pro- 
 cesses and expedients for the recovery of the soda, it may 
 be in place to mention that, the name "sulphate-stuff" is 
 really not correct, as the sulphate, e.g., the sulphate of 
 sodium does not exercise the dissolving effect on the in- 
 crusting constituents, which is done by the carbonate of 
 sodium and the sulphide of sodium while in the prepara- 
 tion of the leach is made first from the sulphate. The 
 soda, which may also be produced from sulphate of 
 sodium, made by the cellulose manufacturer himself by 
 conversion. Therefore the designation, soda-cellulose, 
 is the only correct one. 
 
 For this purpose formerly, evaporating furnaces; were 
 principally used, like those employed in the manu- 
 facture of soda. In Lunges Handbook of the manufacture 
 of soda such a furnace is illustrated, as reproduced in fig- 
 ures 18 and 19. 
 
 In this illustration g is the pan designed for evapora- 
 tion, which is deep and supported by stone pillars, so that 
 
THE MANUFACTURE OF CELLULOSE. 
 
 35 
 
 the bottom of the pan is exposed in order to facilitate 
 cooling off. At the left is the grate a on which the fire 
 necessary for evaporation is maintained. The flames first 
 spread over the fire-bridge, kept cool by the waterpipe c, 
 then over the calcining sole d, over the somewhat higher 
 placed sole e, and finally over the evaporating pan g, from 
 where they are let into the fon of the chimney. The solu- 
 tion makes its way oppositely to the fire; first it is evaporat- 
 ed in the pan, until solid parts separate out, then the mass 
 is drawn out on the side upon the draining sieve i, below 
 which the solution is let off into a reservoir and from there 
 
 
 FIGURES 18 AND 19. 
 
 by means of a pump it is again charged into the pan, to be 
 further evaporated. Through the funnel f, fixed over the 
 first calcining sole, the solid residus are filled upon it, where 
 the last of the water evaporates and after this is accom- 
 plished, it is by means of scrapers drawn into the compart- 
 ment d, and there calcined. After this has been done suf- 
 ficiently, the mass consisting of carbonate of sodium is pull- 
 ed out from the chamber d at its side, and directly into iron 
 wheelbarrows, by which the mass is again carried to< the dis- 
 solving tanks, there dissolved and made caustic, to< be used 
 again in boiling wood. 
 
36 THE MANUFACTURE OF CELLULOSE. 
 
 Another evaporating furnace was constructed by Roeck- 
 ner in Newcastle. Here the leach first flows into a cylin- 
 drical vessel lying horizontally and is there concentrated 
 by boiling. The steam therein cooled gets into a conden- 
 ser and as boiling water it runs into a reservoir. The 
 concentrated leach flows through a pipe, fixed to the bot- 
 tom of the vessel in an open pan on a lower level where it 
 is further evaporated, and from there into a calcining fur- 
 nace, situated below, where the complete conversion into 
 soda takes place. From there, by means of rakes, the mass 
 is pulled into the cooling chamber, arranged below. Here 
 a current of air passes through the hot mass, assisting the 
 combustion of the gases, which are passed into the fire- 
 hearth serving the other parts. By this, the odors, which 
 appear, when the soda is simply discharged from the fur- 
 nace and brought to another place to cool off are avoided. 
 
 To obviate the considerable wearing out of the expen- 
 sive evaporating pans, with the present evaporating ap- 
 paratus, Richard Schneider in Dresden, has constructed 
 an evaporating tower, with movable drizzle faces, con- 
 veniently adjustable (D. E. P. No. 34392), which may be 
 employed to advantage together with furnaces for the re- 
 generation of soda. This furnace consists, — the plant of 
 the gas generator and the chimney not considered, (it is a 
 regenerative gas furnace) — of the firebox H, in which the 
 ignition of the fuel gases takes place and which, accord- 
 ing to construction, may be formed so that it may give off 
 highly heated fire gases or highly heated air separate from 
 each other or together. Further attached to the single 
 or double calcining sole C, at the other end of it, set out 
 with chamottstones like a regenerator, there is a. short 
 chamber R, which during the calcining process is con- 
 tributing substantially, to obtain thorough combustion of 
 all gases escaping from the calcining sole 1 , and thus secur- 
 ing smokeless and odorless working. Next to the chamber 
 R is situated somewhat higher, a quite deep tank D, serving 
 as inspiring pan. Over D the evaporating tower E is erect- 
 ed, with its movable drizzle faces., which ought to have a 
 declination of less than 30 degrees against the horizon. The 
 number of the' drizzle faces depends on the quantity of 
 solution to be worked per unit of time. 
 
 Above C and R there are, for utilization of the radiant 
 heat, a large tank A, from which the smaller tank B, put 
 
THE MANUFACTURE OP CELLULOSE. 
 
 37 
 
 up over the tower E is being fed by pulsometer. The space 
 under C has been arranged for baking and cooling. Into 
 this are pulled from C, through correspondingly construct- 
 ed doors, with which G is. provided, the red hot, but not 
 yet deadbaked masses, which under this system do not need 
 to be raked out in front of the furnace. 
 
 The products of combustion of part of the fuel gases, 
 
 Fig. 20. 
 
 charging H, are carried off through the channel s to the 
 chimney S. The part of the channel s under G is slight- 
 ly vaulted, or still better covered with two layers of thin 
 chain otte plates. This arrangement and construction of 
 s is for the purpose of utilizing as far as possible the heat 
 of passing products of combustion and to keep up and to 
 quicken the calcining process of the masses dropped into 
 (I. The gases therein' evolved (empyreumatic gases), are 
 
38 THE MANUFACTURE OF CELLULOSE. 
 
 by special channels discharged to the fire-hearth and there 
 burned up. The thoroughly calcined dead masses are 
 then at regular intervals corresponding to the different 
 charges, discharged from the different compartments of G- 
 through the doors F and turned over to further manipula- 
 tions. There are further provided at m adjustable open- 
 ings for the inlet of air, and at d for the inlet of the fuel 
 gas. The air entering at m gets heated along the vault 
 over C, and through openings n, it reaches p, there to eith- 
 er cause a perfect combustion of the gases coming from C 
 or to burn the gas entering by d to- increase at times the 
 heat in D. 
 
 The leach to be worked is first run into the tank A, 
 from there lifted to B and, drizzing down the tower in the 
 manner described above and giving off water in the form 
 of vapor, it reaches D, from where in a condensed state it 
 is charged into C, where it is finished. The fire-gases com- 
 ing from H, go the opposite way, as with other evaporating 
 furnaces. The arrangement offers the advantage, that be- 
 sides the saving of a, pan, the total plant ';akes up much less 
 space. 
 
 Herr Carl Keller had previously in the seventies, built 
 a, furnace for the recovery of the soda from straw-stuff 
 leaches, in which the fire-gases were forced by means of a 
 spray of superheated steam over pans arranged like shelves, 
 one above the other. There the hearth and the calciner 
 were under draught, while the back part of the furnace and 
 the part, used for concentration were working under a 
 slight pressure of about 2 mm. water column. This ar- 
 rangement permitted the fire-gases to be led slowly over 
 a, large evaporating surface, which would be possible only 
 to a. limited degree where the draught of a chimney alone 
 was defended on, owing to the elastic steam formed in 
 evaporation. 
 
 For completeness sake it may be mentioned, that an 
 American patent, No, 388,284 by John F. Kennedy, is in- 
 tended to make use of the heat still contained in the cal- 
 cined residues, by arranging a common steam boiler, to 
 produce steam by their radiant heat. Whether this, ar- 
 rangement, has proved a radical success, is not known to the 
 author. 
 
 Another arrangemnet for the production of soda, which 
 has proved very successful in practice, is in operation in 
 
THE MANUFACTURE OF CELLULOSE. 39 
 
 the Cellulose factory Bannkein in Norway and is described 
 by Herr Laur. W. \ensen in No. 11 of the Papier Zeitung, 
 1889, as follows: The regeneration of the salts, contain-' 
 ed in the leaches is thus accomplished in three steps: First, 
 Evaporation of the water until concentration of the leach 
 of 30 degrees B in steam boilers, tubular boilers and pans, 
 whereby the fire-gases are so led against the opposite direct- 
 ed current of the leach, that the fire-gases escaping into 
 .the box give off their heat until as low as 150 to 200°C. 
 Second, inspissation of the concentrated leaches to muddy 
 consistency by open fire in a fire-proof inspissation pan. 
 Third, volatization of the incrustings while melting down 
 the salts in a retort-like furnace, which is so connected with 
 the inspissation pan, that the gases enter the main fire, 
 there being burned up and so assisting in inspissating the 
 leach. The evaporation starts in two steam boilers A, 
 which are connected by a pipe d; the solution is pumped 
 into the boiler through the pipes bb and remains there, 
 until it has reached a certain concentration. The steam 
 evolved in the boilers is in the domes D freed from the 
 leach carried along, by arranging in each of them a sieve 
 with pieces of iron thereon. The solution concentrated in 
 the boilers is, after certain intervals, blown off through the 
 blow-out pipe g and then through the pipe line h is run 
 into the tubular boiler B. 
 
 A steam pipe r, leads the steam evolved in the further 
 evaporation of the solution, from B to the drying cylinders 
 of the paper machine, although the steam may be used 
 for any other purpose. The heating of the tubular boiler 
 is done with the steam which is evolved in the evaporation 
 of the solution in the boiler A, and which gets into the 
 heating tubes by the pipe R' from the dome D. Under nor- 
 mal conditions the solution of from 13 to 21 degrees B is 
 evaporated down to 21 to 27 degrees B in the tubular 
 boiler and then run off into the highest of the four evapor- 
 ating pans C, which originally, set above and against each 
 other, were so built in that the fire-gases, which were strik- 
 ing along the boiler A in the direction of the arrows, were 
 now passing in the direction of the arrows over the lowest 
 pan and further on, on their way to the chimney, over the 
 three other pans. But the gases got cooled off too much 
 and poor draught was the consequence; besides, the space 
 below was needed for a smelting furnace, so the shelve fur- 
 
40 THE MANUFACTURE OF CELLULOSE. 
 
 nace was taken out, and the gases of combustion were 
 passed between two pans filled with solution directly to 
 the chimney. The solution is thus concentrated down to 
 about 30 degrees B and from the lowest pan. through a 
 line of pipe led off into the inspissating tank E. The in- 
 spissating tan T x is a low vaulted compartment, lined with 
 fire-proof material, in which the solution stands as high 
 as the upper edge of the fire-bridge. The plane-grate 
 fire hearth F produces a flame, which by natural draught 
 strikes into the tank and is forced by the vault to strike 
 closely along the solution, whereby the water is further 
 evaporated. Through openings in the long wall of the 
 tank, the solution is continuously stirred while inspissat- 
 ing and thus its dessication is furthered. When the so- 
 lution has become as thick as heavy mud, the fire in F is 
 dumped and the mass pulled out through the openings. 
 It is then thrown into the: retort-like smelting furnace LI, 
 where by firing in the box N, the evaporation of the re- 
 maining water, the continued combustion of the incrusta- 
 tions, and the melting down of the salts takes place. The 
 fire-gases thus make their way as follows: The gases from 
 L, fig. 21, mix with those; from F, strike along the inspis- 
 sating pan E and mix with the flames of the smelting fur- 
 nace LI, fig. 22. The hot fire-gases now strike along both 
 boilers, from back to front, there separate, returning 
 through two fire canals and again coming together strike 
 over the pan C. The fire-gases are on their way deprived 
 of such an amount of heat, that they escape to the chim- 
 ney with a temperature not higher than necessary for the 
 maintenance of the draught. In comparison of the ar- 
 rangements in use in Europe, the one in question offers 
 considerable saving in fuel, by thoroughly utilizing the 
 fire-gases. 
 
 With 1 kilo of coal it is possible to recover 25 kilos pure 
 dessicated salt and yet to have enough steam to dry 15 
 kilos of wood fibre. 
 
 The same Herr Yensen, who has accepted for years the 
 above described plant as satisfactory in practice, much pre- 
 fers an American patent, which Homer T. Yargan has ob- 
 tained for a process of regeneration of soda and which is 
 also protected in Germany by patent No. 42,592. In No. 
 100, Vol. 1888, of the Papier Zeitung, this device is de- 
 scribed as follows: "Here the inspissation is not effect- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 Illiffll to 
 
 41 
 
 <X 
 
42 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 ed by direct firing, but by steam, whereby, it is claimed, 
 the expense for fuel is decreased. Figs. 23 and 24 show 
 the arrangement in the side view and in the plane. The 
 concentration is carried on in three 1 adjoining cylinders. 
 The middle parts of the same, H" W" W'", are closed by 
 sectional walls against the extremities L U L", and A, B, 
 C. The extremities are connected with each other by a 
 number of narrow pipes, which end in the sectional walls 
 and countersect the middle parts. The spent leach to be 
 concentrated is forced by means of a pump through the 
 pipe 0', run into the cylinders at L and flows through 
 the narrow pipes into the other end A. Through the pipe 
 K steam is admitted into the middle part IF, which sur- 
 
 Fig. 23, 
 
 rounds the pipes and gives off its heat through the walls 
 of the pipes to the leach. The water of condensation is 
 continuously let off through the pipe V. The heated 
 leach runs into the chamber A, gives off a considerable 
 quantity of steam and flows in a thickened condition into 
 the chamber E below A, and is forced through pipe TJ 
 into L' fig 24, from whence again, as described above, it 
 flows through narrow pipes to the end of the cylinder at 
 
 B, and from there through pipe U into L" and from L" into 
 
 C. The steam escaping from the leach in the cylinder at A, 
 passes through pipe H into the second middle part IF", 
 and here, as in H" the live steam works through the walls 
 of the narrow pipes upon the leach. The water of con- 
 densation is again carried off through pipe V. The steam 
 
THE MANUFACTURE OP CELLULOSE. 
 
 43 
 
 escaping from the leach in chamber B enters through the 
 pipe J into the third middle chamber H"", to work here 
 in the same manner, as stated before. The steam which 
 continues escaping from the leach in the chamber C is> 
 through the pipe J, drawn into the condensator W of the 
 vacuum pump, while the concentrated leach is carried off 
 by the pump P. 
 
 The vacuum produced by the pump acts on all three 
 cylinders in diminishing degree, so that in the chamber 
 A it is at least and in chamber C greatest. 
 
 As will be seen from the above, fresh steam is let only 
 into the first cylinder H", while in the other, evaporation 
 
 Fig, 24. 
 
 is effected by the waste of steam of the leaches. The quan- 
 tity of steam used will for this reason be small, as one 
 triple-effect Yargan can, for instance, evaporate 15 kilos 
 of water with 1 kilo of coal. The leach is by the Yargan 
 evaporator concentrated to 40 degrees B; the whole of the 
 soda-regeneration is far cleaner than is generally found, 
 besides the attendance of but ten men altogether is nece&- 
 sary in 24 hours to recover the soda for twenty tons of 
 wood fibre, while in the Eankeim apparatus, for instance, 
 for eight tons, twenty men were needed. The Yargan ap- 
 paratus has already proved eminently successful in several 
 American factories. In one of them, for instance, 18 tons 
 
44 THE MANUFACTURE OF CELLULOSE. 
 
 of coal were saved per day as compared with the former 
 method. The very high price of the complete plant is, at 
 present at least, a drawback to its more extensive introduc- 
 tion in Germany. 
 
 Contrary to the soda process just described, the sul- 
 phite process is based on treating the wood with acids, and 
 lately, indeed, with sulphurous acid only, consisting in 
 the combination of one part of sulphur and two- parts of 
 oxygen. It is a gas of strong and pungent smell, which 
 mixed with air, impedes breathing, but is not so absolutely 
 injurious to the human system as one would think, on the 
 contrary, the inhalation of the gas, properly diluted with 
 air and with due precautions, has lately been recommended 
 for consumption, and is for this purpose already employed 
 practically, for instance at the Augusta Victoria Bath in 
 Wiesbaden. 
 
 At low temperature or high pressure the sulphurous 
 acid gas may be transformed into the liquid state. Water 
 absorbs sulphurous acid gas m large quantities, as water 
 itself is also attracted by it from the air. Upon this read- 
 iness to combine with water depends its practical employ- 
 ment, because an aquous solution is the easiest to> handle. 
 The American Tilghman, as stated in the chronological 
 table cited at the beginning, in 1866 first recommended 
 sulphurous acid for dissolving- the incrustations, and he 
 obtained upon a process embodying this feature, the Amer- 
 ican patent being dated October 26, 1867, and the English 
 March 31, 1867. In the American patent the entire 
 method of manufacturing is very exactly and copiously de- 
 scribed, while the Papier Zeitung in 1884, the later prac- 
 tical experiments on a large scale are described. Notwith 
 standing the fact that he had not worked out his inven- 
 tion as much as would have been desirable, he turned his 
 energies to other ideas, so that the promising process of 
 producing Cellulose by means of sulphite solution did not 
 rapidly come into general use. Succeeding Tilghman, 
 Ekman, in Bergvik, Sweden, also discovered a process of 
 producing Celulose by sulphurous acid and he was the first 
 one, who after finishing his experiments, made on a large 
 scale a product fit for use, he first manufacturing secretly, 
 and did not take out a patent until July 13, 1881. In 
 Germany, however, he was preceded by Professor Alex- 
 ander Mitscherluch, who obtained patents not only on the 
 
THE MANUFACTURE OF CELLULOSE. 45 
 
 chemical process of producing Cellulose from wood by sul- 
 phite leach, but also on the different parts of the neces- 
 sary plant. He was very successful in making a great 
 mun Iter of contracts with those paper manufacturers who 
 bought of him his process and who besides obtained the 
 privilege of exclusive rights within certain territories. In 
 consequence of a legal suit, the principal part of Mitscher- 
 lieh's patent No. 4,179 was annulled in 1884 by the Im- 
 perial Court, when it became known that the patent of 
 Tilghman was much older. Besides this, beginning from 
 the year 1893, a vigorous polemic has arisen in the Papier 
 Zeitung as to whether Mitscherlich or C. D. Ekman had 
 first made saleable Cellulose on a large scale, which in the 
 end was decided in favor of the latter. Therefore the note 
 contained in the first edition of this book, that Professor 
 Alexander Mitscherlich was the real father of practical 
 Cellulose manufacture, can to-day no longer be completely 
 sustained, although great credit is due him on account of 
 the practical execution of his ideas and the introduction 
 in business of the process named after him. 
 
 We will first consider how the sulphite leach according 
 to Mitscherlich is made. The sulphurous acid is produced 
 by burning sulphur or compounds containing sulphur. 
 Among the latter is the comparatively cheap pyrite which 
 is composed of about nearly one part of sulphur and one 
 part of iron. When sulphur can be obtained cheaply i. e., 
 cheaper than three times as much of the pyrite would 
 amount to one would decide for the use of sulphur, in the 
 combustion of which a direct loss can hardly happen, while 
 the pyrite after roasting shows at least 4$ unburned sul- 
 phur inside the different pieces, and the loss sometimes 
 reaches 10^. In using solid sulphur the furnace may be of 
 simple construction. A chamber of mason work, the bot- 
 tom of which is formed by a heavy iron plate, will answer; 
 some low iron partitions divide the combustion chamber 
 into several compartments, every one of which is accessible 
 from the outside through doors, so that filling and clean- 
 ing can be done alternately, while working. The furnace 
 is also covered over with an iron plate, which is cooled by 
 water, so that during the process no sulphur can escape un- 
 burned. The controling and regulation of the air supply is 
 done through small shutters arranged in the doors. 
 
 Very often, however, pyrite must be used alone. This 
 
46 THE MANUFACTURE OF CELLULOSE. 
 
 must be broken into pieces with, the hammer as uniformly 
 as possible of about the size of a nut. There are stone 
 breaking machines for this purpose, but they are supposed 
 to give too much clear waste and this must be avoided. 
 When in crushing enough of the fine pyrite has accumu- 
 lated, it may be made use of by mixing it with loam and 
 forming into small balls, which after being thoroughly 
 dried on the furnace, may be charged into the furnace 
 along with the good material, without danger of stopping 
 the grate. It should be mentioned at this point, that 
 Herr Maletra has constructed a plate-furnace, which is em- 
 ployed with advantage principally for roasting fine pyrite 
 and especially dust. 
 
 The broken pyrite before using has to be s bored in a 
 place as warm and dry as possible, but in the room where 
 the furnace stands. Such pyrite furnace is illustrated in 
 figs. 25, 26 and 27. The furnace is almost quadratic, the 
 inside laid out with Chamotte brick, about 1.5 meters wide, 
 spanned over by a flat Chamotte vault, with an opening 
 in its zenith for the outlet of gases, which next enter a 
 space between the first vault and another one spanned over 
 the first one. Because, as a rule according to the extent 
 of the works, three, four, or more pyrite furnaces are 
 placed side by side, or still better, with their backs against 
 each other, not all of which, however, are worked at the 
 same time, they must be connected with each other and 
 with the different towers later on described. This is done 
 by arranging above the furnace two canals, the . one of 
 which is by the opening A, the other by the opening B 
 connected with the interspaces mentioned. Both are 
 closed by peculiarly constructed valves, similar to water 
 sealed valves, only that in this case on account of the heat, 
 not water, but sand, or fine pyrite is employed as a means 
 for sealing. The second vault mentioned also serves the 
 purpose of protecting the inner one against cooling off. 
 About one-half meter from the floor is a grate, consisting 
 of single, strong, square bars, arranged quite close togeth- 
 er, which by means of a key fitted to the front end can 
 be turned, and thus during roasting, the 'cleaning of the 
 grate, i. e., the falling through of the slake is possible. 
 The front opening through which the turning of the 
 grate bars as well as the pulling out of the finished pyrite 
 is performed, and likewise the fire door itself, which serves 
 
THE MANUFACTURE OP CELLULOSE. 
 
 47 
 
 for the feeding of fresh pyrite are provided with well- 
 fitting doors, which as a rale are luted besides with loam. 
 
 They are also provided with a small hole, closed with a 
 shutter or glass plate, through which the process is con- 
 
48 THE MANUFACTURE O'F CELLULOSE. 
 
 struction may be observed at any time. This process after 
 the furnace has once been started, goes on in the following 
 manner: To the burning pyrite, kept at light red heat, 
 enters atmospheric air, the oxygen of which combines with 
 the iron from oxide of iron, and with the sulphur to form 
 sulphurdioxide or sulphurous acid. Hence the regulating 
 has to be managed so that not too much air enters, but 
 enough to maintain the furnace at intense red heat. Care 
 must also be taken that the pieces of pyrite all get thor- 
 oughly burned through, so that only iron oxide and not 
 part of the sulphur is thrown on the slake-pile, what 
 eventually would amount to considerable loss. Insufficient 
 air supply has besides the disadvantage, that sometimes 
 separation of uncombined sulphur takes place, the so-call- 
 ed sublimation, which can be of much damage in the later 
 digesting process. In order to obtain in the next manipu- 
 lation a most concentrated solution of sulphurous acid, the 
 gases leaving the pyrite furnace, must contain as much 
 sulphurous acid as possible and this can be only when the 
 air supply is limited to the least necessary quantity, when 
 the gases themselves possess a temperature as low as pos- 
 ible. Therefore they are not let directly into the tower, 
 which is necessary in the making of leaches according to 
 the system of Mitscherlich, but they are cooled off bv lead- 
 ing them m heavy pipes, up to about two-thirds, or three- 
 quarters of the height and down again to the foot of the 
 tower. For this reason a less strong solution always re- 
 sults in the summer months than in winter, which must 
 be called a disadvantage in regard to uniform working. 
 This may be somewhat remedied by continuously letting 
 water drizzle down the outside of the before mentioned 
 cooling pipe, though this is far less effective than the cold 
 of the winter. 
 
 What influence the temperature has on the production 
 of the leach can easily be seen from the following - little 
 table, showing the capacity of the water for absorption at 
 different degrees of temperature: 
 
 Water of 2°, 4°, 6°, 8°, 10°, 12°, 14°, 16°, 18° 
 absorbs 75, 70, 65, 61, 57, 53, 49, 45, 42 
 
 cubic centimeters of sulphurous acid gas. 
 
 At the above mentioned ascending pipe, near the fur- 
 nace two small branches (T's) are advantageously arrang- 
 ed, which are connected by a glass tube, like the water- 
 
THE MANUFACTURE OF CELLULOSE. 49 
 
 indicator on steam boilers, so that the circulation of the 
 gases, coming from the pyrite furnace, can be observed. 
 When sublimation has taken place and consequently sul- 
 phur is untainted in the gases, a yellow coloration will 
 show upon the glass and then better draft must at once 
 be secured i. e., some air must be admitted. To transform 
 the gaseous sulphurous acid into the aqueous solution, 
 mentioned before, it is necessary to lead the gas against a 
 fine shower of water; the aqueous sulphurous acid so ob- 
 tained is, however, very unevenly composed and little suit- 
 ed for the subsequent process of digesting. For this 
 reason it is preferred to use combinations with bases, which 
 can be easily stored, and for practical reasons the com- 
 paratively chear* lime-stone, easily obtainable and some- 
 time also magnesite, were chosen. Mitscherlich recom- 
 mends lime of rather porous condition, so that a large sur- 
 face is presented, which, however, must not be too soft,. 
 as it would then dissolve too quickly, become muddy and 
 cause clogging of the tower. The lime-stone is broken up 
 into pieces of about 100 m. m. diameter. Other factories, 
 working the same system, do not use tufa, but dolomite 
 and jura lime, and, as they claim, get further with them,, 
 on account of their greater hardness. Carl Kellner first 
 used dolomite and had the process patented. 
 
 The tower, which is tne characteristic sign of most Cel- 
 lulose works, is constructed in the following manner: 
 
 Fig. 28 shows an outside sketch of it, and fig. 29 the 
 ground plan. Upon a strong square foundation are built 
 two, and sometimes four or more reservoirs of masonary, 
 open at the top, over which are set the wooden towers. 
 These towers of 30 to 35 meters in height are formed by 
 setting single barrels, properly cylindrical tubes of best 
 resinous pine, bound by iron hoops, on top of each other, 
 packing the joints with waste and coating the whole heav- 
 ily with tar. Because the lower parts have to stand great 
 pressure on account of the lime charge, representing ac- 
 cording to the width (as a rule one meter) and height of 
 the tower a weight of over 1,000 C, the thickness of the 
 lower walls must be made heavier and also the number of 
 hoops must be increased where the dimensions are great- 
 er. Directly over the stone reservoirs, near the top of 
 which the gases of combustion enter from the pyrite fur- 
 naces and at the bottom of which the finished aqueous 
 
50 THE MANUFACTURE OF CELLULOSE. 
 
 solution is let into the leach reservoirs, is laid a heavy- 
 grate of oak, the single beams of which are narrower at 
 the tower side. That the great weight of the lime shall 
 not rest thereupon alone, two other heavy beams go square 
 through the tower, being supported from the outside. At 
 the upper end of each tower is a water reservoir, fed from 
 below by a pump, from which a stream of water, regulated, 
 as required by a cock, can be discharged on the lime. It 
 must also be made possible by means of a valve or other- 
 wise, to let a larger quantity of water even to the whole 
 contents of the reservoir run down at once, when it be- 
 comes necessary to rinse cut the tower. Close below the 
 water tank is a side opening through which the lime is 
 filled in. This must be made so that it may be securely 
 closed and there must also be some smaller openings ar- 
 ranged at different heights. The different towers are sur- 
 rounded and held together by a strong frame work, divided 
 in stories, connected by stairs and roofed over on top, so 
 the whole forms a single ball tower, which offering a large 
 surface to the wind, must certainly be well anchored to 
 the ground by wire ropes. In the uppermost story there 
 is generally a balcony from which the lime buckets, pre- 
 viously hoisted up by a windlass, are carried to the fill- 
 hole. Where power is convenient it is better to have the 
 hoisting done by a mechanical elevator. For practical 
 reasons it is well not to delay the first filling of the tower 
 until it is finished, as the grate suffers, when the lumps of 
 lime fall from so high a distance; the lime itself gets 
 crumbled and thus in the beginning might cause clogging, 
 but to charge the different sections as the tower is build- 
 ing up. There has but to be mentioned that the ascend- 
 ing iron pipe at its upper end, where it forms the ell, is 
 provided with a cover, which must be well luted. This 
 cover is opened, when a newly started furnace is getting 
 warmed up and is not closed until the pyrite is burning 
 with a blue flame, and the charge is consequently in good 
 order. After that the gaseous sulphurous acid is 
 permitted to enter the tower, drawing upwards against the 
 water, flowing over the lime. 
 
 Along the walls of the tower there will naturally be 
 large spaces, not filled out with lime, also the water will 
 not everywhere evenly wet them and thus the upward 
 drawn sulphurous acid would become unequally absorbed. 
 
THE MANUFACTURE OF CELLULOSE. 51 
 
 Fig\ 29. 
 
 Fiff. 28. 
 
52 THE MANUFACTURE OF CELLULOSE. 
 
 To prevent this, several protruding rings are fixed to the 
 walls, inside of the tower, against which the gases must 
 strike and by which also the water, which might otherwise 
 run down the walls at certain places only, is turned off 
 towards the centre of the lime charge. By the contact of 
 the sulphurous acid with the lime taking place on the long 
 run through' the 1 tower, sulphite of lime is next f ormed, where- 
 by the carbonic acid of the lime is set free. Then the sul- 
 phurous acid is dissolved by the water and this again dis- 
 solves the sulphite of lime, which is soluble in water, only 
 with difficulty, and thus bisulphite of lime is formed. As al- 
 ready mentioned, the temperature is of great importance 
 in the chemical process, and also the supply of air in the 
 process of combustion; this, therefore and the quantity of 
 water running down must always be taken in consideration, 
 because also on this depends the concentration of the 
 leach. When too- much water is admitted, the resulting 
 product, the aqeous solution of bisulphite of lime, would 
 be too weak. From the stone reservoirs in the foundation 
 of the tower, this solution is now let off through a lead pipe 
 int large wooden tanks, which are best placed so< high, that 
 afterwards the leach can be run through a line of pipes 
 directly into the digester. Where the local conditions do 
 not permit this, it is best to use a reservoir of mason work, 
 well covered, from which the leach, when needed, can be 
 pumped to' the digesters. In this case it is advisable to 
 first catchj the leach in a barrel, because it is necessary 
 during the concentration of the leach to have it measured 
 quite often with the areometer by the man employed at the 
 pyrite furnace, and also by the technical officials, so that 
 when the leach comes too weak, the fault can at once be 
 remedied. The average strength is 4 1-2 to 5° B in sum- 
 mer, but in winter 7° and more. 
 
 If the preparation of the leach has gone satisfactory, the 
 areometer indicates the proper strength of the leach in 
 bisulphite of lime; but when sublimation has taken place, 
 polythionic acid is formed in the tower (according to D. 
 Frank, this is impossible) the compounds of which are 
 harmful in the digesting process, while in the leach they 
 are estimated wrongly as bisulphite of lime, consequently 
 the concentration is measured stronger than it is in fact. 
 
 In this process there has repeatedly occurred a clogging 
 of the tower; it takes place after one or two* days> some- 
 
THE MANUFACTURE OP CELLULOSE. 53 
 
 times oftener, when the lime partially dissolved by the acid 
 and washed together by the water accumulates below on 
 the grate, or at any other place, and renders the passing 
 of the gases impossible. Draft is then wanting and the 
 furnaces smoke, i. e., the gases come out at the joints, The 
 other tower must then be put to work at once. The im- 
 pediment may be removed by opening a door arranged 
 directly above the grate, pulling out the lowest layer of 
 stones and rinsing the tower once or several times. The 
 same result may be achieved by causing the whole lime 
 charge to slide, when the pieces change their position and 
 the working order is restored. As soon as the lime charge 
 in the tower has somewhat settled, new lime must be ad- 
 ded. The pieces pulled out in cleaning the tower, if not 
 too small, and after being well rinsed, may be mixed with 
 fresh lime and filled in again. 
 
 For every plant, besides the towers just described, anoth- 
 er smaller one, a so-called "drive-over-tower," is necessary, 
 which is filled with the waste pieces of lime. This tower 
 has a smaller diameter, and need not be as high as the oth- 
 ers. It often consists of kerosene or oil barrels, set one above 
 the other. In the sketch in fig. 29 it is marked with A. It 
 is provided with grate and water arrangement like the oth- 
 er towers and is only used when an operation of digesting 
 has been finished and the sulphurous acid gas, under pres- 
 sure during boiling, must be blown off. The digester is 
 connected with the small tower by a lead pipe. As soon 
 as the water in this tower has arrived at the lowest part, 
 the blow-off valve of the boiler is opened; the gaseous sul- 
 phurous acid rushes against the water and as long as the 
 blowing off continues, forms a strong leach of about 12°, 
 which often very much increases the concentration of the 
 leach already in the basin. 
 
 In place of the high towers recommended b^ Mitscher- 
 lich, which are certainly the cause of many inconveniences, 
 but which must be high, because the sulphurous acid re- 
 quires much time to decompose the carbonates and to 
 transform them into sulphites. Later on two towers' were 
 recommended, which are also quite satisfactory, when mag- 
 nesite is used instead of lime. The tower need then to be 
 but five to six meters high. Professor Hager in "Fabri- 
 kation des Papiers," page 203, writes in regard to this as 
 follows: The ball towers cause a. multitude of discomforts 
 
54 THE MANUFACTURE OP CELLULOSE. 
 
 and uncertainties in working, not only because of the hoist- 
 ing of the raw material to such a considerable height, but 
 mainly also for the reason that on account of the great 
 weight the lower pieces, already become softened, get 
 crumbled and render difficult the ascent of 
 the acid gas. Because in addition to this 
 tall towers are expensive to build on account of the 
 foundation, etc., it has been recommended to build in place 
 of one high tower several low ones, for instance of six to 
 eight meters high, adjoining each other and connected by 
 pipe lines in such manner, that the acid not absorbed in 
 one tower, is caried to the next one, and so on. But even 
 this arangement has its disadvantages, as in this manner, 
 if the most careful regulation of the water supply is not 
 absorbed, sulphite solutions of much varying concentra- 
 tion are obtained, because in- the last tower but little acid 
 is left for absorption. But as time for action can be pro- 
 cured for the gas by giving great square dimensions to the 
 tower, it seems well considered to employ, instead of tall 
 and narrow towers, low and wide ones of a shape deviating 
 from the cylindrical; especially when it is considered that 
 a saturated sulphite solution, is best obtained by successive 
 strengthening up, and by the meeting of unweakened gas 
 with the sulphite, immediately before leaving the tower. 
 For this purpose, at the point, where the gas first comes 
 in contact with the material, the tower should not be wide, 
 but above this point it should gradually become wider to 
 give the gas much time for action, and should then become 
 narrow again towards the top, to increase the velocity of 
 the gas in proportion to its decreasing strength. 
 
 The tower built on this principle, illustrated by fig. 30 
 consists of two cones, the lower one inverted so that they 
 are joined at their greatest diameter, which construction 
 offers the advantage that with less height 
 a considerable charge is possible while the 
 walls of the lower cone form a support for the 
 raw material, which now settles down as it gets dissolved, 
 without danger of clogging of the drain-holes, which are 
 arranged at b, and which widen towards the lower side. In 
 such manner, with a tower of but about 7 meters total 
 height, a capacity of 7.5 cubic meters is gained, when the 
 dimensions in the proportion as given in the sketch, are 
 followed. In the sketch can also be seen the inlet pipe for 
 
THE MANUFACTURE OF CELLULOSE. 
 
 55 
 
 the gases at a, the reticulate vault at b, the opening at c, 
 for the charging of the raw material, which can be closely 
 shut by an asphalted or annealed iron plate, the outlet pipe 
 for the gases at d, and the sprinkling arrangement at e, 
 with the water supply pipe at r. The vessel A into which 
 the sulphite solution is running from 0, is practically ar- 
 ranged in the vault Gr, outside of the axis of the tower, so 
 that by removing the coverD, it can be cleaned of the un- 
 dissolved particles of earth carried along and accumulating 
 there. The emptying is either clone through a lead pipe, 
 
 Fie:. 30. 
 with a stop, or by a lead syphon. It is necesary to take 
 care that the gas is completely absorbed on account of its 
 damaging influence on vegetation and to let the air, com- 
 ing from the tower, before it escapes into the atmosphere, 
 pass through a mass, which absorbs the rest of the acid. 
 For this purpose milk of lime or a soda solution is used; 
 which is conformingly kept in a vessel placed at f, which 
 can be hermetrically closed. Into this the air from the 
 tower enters through the pipe r, and after circulating 
 through the solution leaves through the pipe g. After the 
 
56 THE MANUFACTURE OP CELLULOSE. 
 
 solution has become saturated, it can be directly let through 
 pipe r into the tower, when making sulphite of lime. But 
 if soda lye is contained in tank f, the sodium sulphite ob- 
 tained is filled into glass vessels to be used as antichlor. 
 TO prevent damaging the inside lead lining of the tower, 
 which is easily done when filling in the raw material, it is 
 advisable to cover the lower cone with wooden slats, which 
 also form gutters, permitting the sulphite solution to run 
 off. It will answer, however, if instead of this arrange- 
 ment the walls of the tower are protected by a coating of 
 tar or asphalt. Whether practical experiments have been 
 made according to this proposition is not known to the 
 author. 
 
 Another method for the preparaton of sulphite leach, in 
 which, however, the tower system is also employed, is the 
 one according to the process of Ritter-Kellner. Herr 
 Kellner has, according to his own personal statement, by 
 accident indeed, but independent of Mitscherlich, discov- 
 ered the most profitable application of sulphurous acid ~n 
 the manufacture of cellulose, and so perfected it, that at 
 present a greater number of the cellulose manufacturers 
 work according to his instructions (which, however, have 
 been amended by some in many directions) and manufac- 
 ture a product, which in certain respects indeed differs 
 from Mitscherlich cellulose, but which is excellent. 
 
 In Hoyers work, page 214, the schematic drawing of 
 this system,, as taken from the French patent No. 157,754, 
 is illustrated, as far as the leach making is concerned, and 
 the following description is given: The making up of the 
 sulphite is carried on in a circular run, beginning with the 
 solution of the sulphite of lime in weak sulphuric acid, un- 
 tainted in the tank A, running into tank D through pipe a, 
 and on its way passing an injector at B, to draw along sul- 
 phurous acid gas, purified and cooled, through the' pipe R, 
 connected with the sulphur burner and thus saturated 
 reaching tank D, charged with lime stone. In this tank 
 is a false bottom, below which the sulphite solution accum- 
 mulates, which by a pump P, is forced up into tank A, and 
 kept in circulation, until it has reached the proper strength, 
 to be then let off through the leaden faucet h. The car- 
 bonic acid liberated from the carbonate of lime in D, and 
 the unabsorbed sulphurous acid and finally the air, coming 
 from the sulphur and pyrite furnaces., reach partially the 
 
THE MANUFACTURE OP CELLULOSE. 
 
 57 
 
 water tank G, through the pipe R", and its branch R", and 
 partially enter again into circulation, drawn up by the in- 
 jector B through pipe R. As the end n of pipe R", is per- 
 forated and laying in the water tank C, the rest of the sul- 
 phurous acid is absorbed by the water, while air and car- 
 bonic acid go off free. The water contained in C is then 
 through the pipeb, provided with a valve for regulating and 
 the injector pipe a carried to the absorption apparatus and 
 used to dissolve the sulphite. According to another ar- 
 
 Fig. 31. 
 
 rangement (fig. 32) towers are also used and in such man- 
 ner, that the sulphurous acid gas is drawn from the furnace 
 by a steam injector and first carried to a large low horizontal 
 chamber A, to get rid there of the dust carried along and to 
 cool off, to which purpose the chamber is provided with 
 partition walls, forming a labyrinth and covered by a tank 
 B, in which is cold water. Then the gas passes through a 
 coil C and enters in the ordinary way, into common towers 
 I and II, filled with lime stone. Above the first tower I there 
 is a tank D, into which is pumped from E the weak sul- 
 
58 THE MANUFACTURE OF CELLULOSE. 
 
 phite solution, obtained in the tower II and run into tank 
 E, to be thus repeatedly exposed to the gas, by drizzling 
 down this tower instead of water. But over the second 
 tower a water reservoir F, is arranged, from which a shower 
 of water runs down the tower II. To bring into circula- 
 tion again the sulphurous acid not absorbed in the tower I, 
 there is a connection made between both towers by a pipe 
 r, through which the gas accumulated in the upper space of 
 
 tower I gets into the lower part of tower II. Through the 
 pipe s the concentrated solution flows into cisterns, and 
 through pipe t, carbonic acid, air, etc., enter the open at- 
 mosphere. 
 
 One can see from the description, that the preparation of 
 
THE MANUFACTURE OF CELLULOSE. 5» 
 
 leach, according to this system, is much similar to the 
 Mitscherlich system, but m some respects appears much 
 more rational, because by connecting two towers (which do 
 not need to be very high) and arranging some pipes, be- 
 sides pump and injector, a circulation is produced, by 
 means of which a more equal concentration of the leach 
 can be obtained, more easily and safely, which in regard to 
 the subsequent process of digestion, must be considered an 
 advantage. 
 
 Since the appearance of the first edition of this book the 
 author has by personal observation in factories in Saxony 
 and Bohemia, become extensively acquainted with the sul- 
 phite process according to Kitter-Kellner. 
 
 The leach plant, according to Kellner, as carried out in 
 practice, is illustrated in fig. 33 and 34, as contained in set 
 1894, page 2,683, of the Papier Zeiting. This plant repre- 
 sented on a scale of 1:200, consists of two or more wooden 
 towers or saturation tubes I and II, built vertically one next 
 to the other, which are connected by the stone ware pipe S. 
 
 The filling material rests on grates, A in fig. 33, and is 
 to be selected according to the nature of combinations to 
 be made. It is recommended in the Kellner method, to 
 fill the towers either with Dolomite in order to produce a 
 doublesalt of acid-sulphite lime-magnesia or with carbon- 
 ate of lime to make lime bisulphite. 
 
 Above these towers are the tanks Tl and T2, of which Tl 
 is filled with fresh water and T2 with the solution from 
 tower I. The outlet from these tanks into the overflow 
 cups U below is regulated by an arrangement adjustable 
 from below. The overflow cups also serve to distribute 
 the sprinkling of the pieces of lime uniformly and offer 
 the advantage that they do not easily get clogged up like 
 sprays and distributing pipes. Ml and M2 are vessels of 
 brass in which the concentration and quality of the solu- 
 tions running out of the towers I and II are measured. 
 
 The sulphurous acid gas, coming from the sulphur acid 
 pyrite furnaces runs in the direction of the arrows through 
 the sublimatory K, and is drawn off by the injector D 
 and blown through the cooling pipes Dl. These are laid in 
 a cistern, into which water is flowing from pipe 1. At 
 the other end just as much water is running off through 
 the canal 11. The well cooled gases then enter the tower 
 
60 THE MANUFACTURE OF CELLULOSE. 
 
 I from below up to El, spread along the stones in there, 
 sprinkled with water from above, find their exit above at 
 E2, a mixture of sulphurous acid gas, carbonic acid, nitro- 
 gen and air and are carried downwards through the stone- 
 ware pipe S, until at E3 they enter the tower II there to as- 
 
 W Fig. 
 
 cend again and to be completely absorbed. The unabsorb- 
 ed gases, like nitrogen carbonic acid and air escape through 
 pipe C into the open air. 
 
 The sublimatory K is a low tower, tightly closed, by a 
 partition divided into two chambers. These chambers are 
 filled with non-corrosive material, like pieces of brick, 
 basalt stone or cake, which rest on grates and offer a large 
 
THE MANUFACTURE OF CELLULOSE. 
 
 61 
 
 surface to the sulphurous acid gas passing through for the 
 disposition of the sublimed sulphur. In the wall trap 
 
 doors and others for cleaning are provided and it is of 
 
62 THE MANUFACTURE OF CELLULOSE. 
 
 advantage to have the covers consist of pans, which are 
 cooled with water circulating through and cool off the gas 
 passing through the chamber. 
 
 While the gases are circulating as described, water is let 
 into the tower II from above, i. e., opposite the entering 
 of the gases. It sprinkles the limestones, leaves the tower 
 at r2 and runs as weak solution through pipe r2 and meas- 
 uring vessel M2 into the tank K2; from this it is forced 
 by the pump P into the upper tank T of tower I, from there 
 it runs into the tower sprinkling its charge and leaves it, 
 as finished leach, to run off through pipe rl and measur- 
 ing vessel Ml into the tank E. A second pump PI forces 
 the leach from there to the -ligesters. 
 
 Later Henry Kellner designed and installed several 
 other methods of preparing leach. In a large German 
 factory for instance he draws the sulphurous acid from the 
 pyrite furnaces, forces it through a wash vessel and 
 then through four wooden tanks, placed one above the 
 other, in which are limestones and which are filled with 
 water, which, following the law of gravitation, flows from 
 one tank into the other and runs off below as finshed leach. 
 On page 2,714 set 1894 of the Papier Zeitung is described 
 and in fig. 35 and 36 are here illustrated, such a battery of 
 tanks, as working advantageously in Waldorf near Mann- 
 heim, the largest cellulose works of the world. This tank 
 method depends on absorption of the masses and consists 
 in forcing the purified and cooled gases by a compressor 
 through the tanks, containing water and limestone. The 
 solution runs from one tank into the other. The tanks 
 I to V are so arranged that the solution therein contained 
 can, through the connecting pipes w2 and w5, provided 
 with valves, flow into the next one, until reaching V. The 
 water flows through pipe Wl into tank I, which like II, 111 
 and IV is provided with a perforated false bottom on which 
 the limestone charge rests. The sulphurous acid gas com- 
 ing from the compressor, consequently under pressure en- 
 ters through pipe g, into the lowest tank V, which receives 
 the solution from tank IV, but does not have a false bot- 
 tom nof a limestone charge. The acid not absorbed by 
 this solution goes through the lead pipe g5 into the coil 
 under the false bottom of tank IV through the openings 
 of which it is evenly distributed over the tank. Likewise, 
 the unabsorbed acid goes through pipes g4, g3, g2 until 
 
THE MANUFACTURE OF CELLULOSE. 63 
 
 reaching tank I, from where any remaining gas is again 
 carried off through pipe gl. The gas pipes, g5 and g4, 
 
 Figures 35 and 36. 
 
 are carried as high as shown in the sketch, in order that 
 
fi4 THE MANUFACTURE OF CELLULOSE. 
 
 no liquids from the higher tanks can run into the lower 
 ones. When the plant is managed rightly nothing hut 
 air devoid of acid, should leave here, as it should be ab- 
 sorbed by the liquid, through which it is circulated. The 
 solution arriving in V, there takes up sulphurous acid only, 
 but no lime, and runs off through the leach measure P. 
 Each tank is provided with a manhole of hard lead and 
 a gauge glass. Stairs facilitate the access to all paxts. 
 
 In American factories he has further introduced a 
 method by which in low absorption towers, connected with 
 each other counter-current, aqueous sulphurous acid is 
 first prepared, which is then saturated with the desired 
 quantity of the base in tanks filled with limestone, and 
 methodically connected in series. 
 
 The importance which D. Kellner has from the start 
 paid to the proper cooling of the sulphurous acid gas from 
 the furnace, may be inferred from the dimensions, which 
 he gave to the respective cooling arrangements. The man- 
 ager of one of the oldest Bohemian factories, planned after 
 his system made to the author the concerning statement 
 that Kellner had recommended a system of pipes, 14 me- 
 ters long and 3 meters wide, presenting a cooling surface of 
 from 55 to 60 square meters. Besides, when these cooled 
 gases are drawn by means of a pump through the one or 
 several towers thereby rendering the saturating of the 
 water entirely independent of the draft in the tower, the 
 formation of the leach becomes much more uniform than 
 is possible in the Mitscherlich process. 
 
 In connection with this it may be mentioned that some 
 factories, and especially those working the Ritter-Kellner 
 system, use commercial liquid sulphurous acid, either ex- 
 clusively or as a reserve, for convenience or uniformity. 
 This is stored in a strong vessel, provided with pressure 
 gauge and gauge glass, and can be used any time, either 
 directly or to improve the leach from the tower, when it is 
 too weak. In most instances, however, the liquid sulphur- 
 ous acid comes too high and besides much care has to be 
 observed in transportation during summer, because direct 
 sunlight may cause so much heating and also evaporation 
 of the sulphurous acid that there is danger of explosion. 
 The accident in the cellulose factory in Ober-heschen, some 
 years ago, should be a warning. Sometimes it is com- 
 
THE MANUFACTURE OP CELLULOSE. 65 
 
 plained that much sulphuric acid is still contained in the 
 liquid sulphurous acid. 
 
 Lately Dr. Kellner has recommended still another dis- 
 solving method, i. e., to employ gaseous chemicals instead 
 of liquid leaches. In the Papier Zeitung the following 
 statement has been made by him: Until recently the veg- 
 etable materials used for the manufacture of cellulose were 
 treated with liquids suitable 10 dissolve and decompose its 
 incrusting constituents. This has the disadvantage, that 
 a very large quantity of the liquid chemicals, as well as 
 their employment under pressure or high temperature is 
 necessary. The present invention concerns a method by 
 which the production of cellulose can be attained with 
 much less expense in chemicals and without the application 
 of pressure or high temperature (except in some cases, 
 where the structure of the plants is especially dense); re- 
 sulting in considerable saving and besides a much less 
 weaker end product. 
 
 This process is characteristic in this, that the chemicals 
 which are to decompose the incrusting substance of the 
 vegetable materials, are brought in contact with them in 
 gaseous condition. For this purpose all those chem- 
 icals, are suitable which exercise upon the incrusting sub- 
 stance a hydrolytic or oxydizing influence, especially nitro- 
 gen-oxide, nitrous-acid, nitrogen, peroxide and chlorous 
 acid. In working this process, the more or less dry veg- 
 etable materials are if necessary previously steamed and ex- 
 posed to the action of these chemicals in vessels, made re- 
 sistant to the gases and vapors mentioned. 
 
 The vegetable material treated in this manner is then, ac- 
 cording to the kind and quality, worked with cold water or 
 steamed, or else put under mechanical treatment (in mills, 
 etc.), after which they are treated with an alkaline solution in 
 order to dissolve in the alkalies the incrusting substances pre- 
 viously decomposed by the gases and vapors. The so treat- 
 ed vegetable material is then violently agitated by ma- 
 chines such as are used in the paper industry, in order to 
 get the cells laid free by the treatment, out of their par- 
 allel position. After this the produced cellulose is washed 
 and if necessary, bleached. 
 
 It is of special advantage to expose the vegetable mate- 
 rial treated with the gaseous and vaporous and gaseous 
 oxidizing means, after washing with water, to the action 
 
66 THE MANUFACTURE OF CELLULOSE. 
 
 of amnionic vapors, because the ammonia can easily be 
 recovered in a pure state of heat. With some kinds of 
 wood, carbonate of soda or caustic soda, must be used to dis- 
 solve the incrusting substances; in such case the alkaline 
 solution is advantageously added at the same time, when 
 worked in the roll or stamping mill, because using the lat- 
 ter requires but a small quantity of the alkaline solution 
 and it is quickly distributed through the vegetable mate- 
 rial. 
 
 To avoid the repeatedly mentioned disadvantages of the 
 towers and to be able to use with more convenience the 
 burned lime, which combines more readily with sulphurous 
 acid, a number of vessels filled with milk of lime, were put 
 in use and thus the so called chamber apparatus was 
 formed. The chambers of mason work, closed on top-, are 
 to three-quarter of their height filled with milk of lime, 
 through which the gas, coming from the furnace, has to 
 pass. To this purpose partition walls go from the top 
 down near to the bottom so that in every chamber the 
 sulphurous acid gas is forced to pass downwards through 
 the milk of lime and to rise up again. Because by itself 
 this would not go on quickly enough, a ventilator is used 
 as a rule, which is placed behind the last chamber, caus- 
 ing a draft. In the same place an injector is often used, or 
 a chimney to create the necessary draft. This chamber 
 system has been brought to the greatest perfection by W. 
 Flodquist in Gothenburg, who has placed 10 chambers in 
 a series so arranged that the solution is circulating through 
 the chambers until it possesses the required strength of 
 5°B. 
 
 A method quite similar to the chamber system has been 
 patented by the Englishman, Dougall. The American 
 patent No. 311,595 was described in the Papier Zeitung, 
 with illustrations, represented in fig. 37: The process con- 
 sists in burning sulphurous or pyrite in strong retorts, into 
 which, after the sulphur has started burning, compressed 
 air is introduced by means of a powerful blower. The 
 sulphurous acid thereby produced is by a system of pipes 
 let into a number of vessels, which are filled with water 
 or alkaline solution. In these vessels the gases are brought 
 in contact with the liquid and the absorption so effected. 
 Instead of this arrangement an exhauster may be used at 
 the opposite end, which draws the air through the retorts, 
 
THE MANUFACTURE OF CELLULOSE. «7 
 
 In every case, the temperature of the retorts is kept as low 
 as possible, so that few gases can escape. For this pur- 
 
 pose, the retorts in which the burning of the sulphur is af- 
 
68 THE MANUFACTURE OF CELLULOSE. 
 
 fected, axe surrounded by a water jacket. The pipe sys- 
 tem, carrying the gas to the saturation tanks, is also pro- 
 vided with a water cooling device. The sulphurous acid 
 gas is entering, into the tanks directly below the water 
 level. These tanks are provided with stirring arrangement. 
 By the aid of this explanation the different parts of the 
 plant can be easily found in the sketch. A is the blower, 
 which drives the air through the retort B. After the sul- 
 phur inside the retort has been lighted with a hot iron, it 
 receives a liberal air supply from the blower, and the com- 
 bustion goes on at once without being further assisted by 
 outside heat. Overheating, which would be detrimental to 
 the process, is prevented by the water jacket Bl. The pipes 
 next connecting to the retort B are also provided with a 
 water jacket, Bl. The pipe C then carries the gas to the 
 tank E, in which the stirrers H, are arranged, so that the 
 liquid comes in close contact with the gases. 
 
 A number of such tanks E communicate by the valves 
 SI, S2, S3 etc. As long as the circulation of the gases is 
 going on these valves are closed. The water or the dis- 
 solving agent is filled in the last tank through the pipe F. 
 Before the gas is blown in, the tanks are filled through the 
 valves S, so high that the pipes B are considerably below 
 the level and the gas is driven right into the liquid. The 
 gas in excess is carried off from the last tank through the 
 pipe D. To control the height of the liquid in each tank 
 and for the taking of samples, glass tubes GfGf, with cocks 
 are provided. The work proceeds in the manner, that the 
 gas is driven through the tanks until the solution in the 
 first tank has reached the desired point of saturation. The 
 blowing is then stopped, the liquid is run off from the first 
 tank and by opening the valves S ( 2, S3 and F, it is filled up 
 to its former level. The blowing is then started again and 
 continued until a solution of the required strength is again 
 obtained in the first tank. The number of the tanks must 
 be made large enough so that through the pipe D but a 
 small excess of sulphurous acid can escape. Previous to 
 DongalPs invention, W. Y. Turner had in 1872 obtained a 
 patent on forcing air through closed sulphur furnaces. 
 
 Upon nearly the same principle is based a leach ap- 
 paratus, which Dr. A. Frank in Charlottenburg, has de- 
 signed and which does not have the drawbacks of the 
 methods so far described. In a lecture, which Dr. Frank 
 
THE MANUFACTURE OP CELLULOSE. R9 
 
 delivered at the convention of the cellulose manufacturers 
 at Berlin in 1887, the advantages of his plant were pre- 
 sented and about the disadvantages of the principal former 
 methods for leach-making the following was said: "Con- 
 cerning the tower it must be admitted that in principle, 
 they represent the simplest plant, in practice, however, 
 first, the depending of the draft, and with it, of the whole 
 plant, on the outside weather conditions cause much 
 trouble, and in many instances this has necessitated the 
 providing of ventilating arrangements worked by ma- 
 chinery. It is not less a drawback, that but few limestones 
 are perfectly suitable for the filling of the towers, as too 
 hard a stone dissolves too difficultly in the weak acid, while 
 soft or impure stones sink together and hinder the free pas- 
 sage of the gas. Another important shortcoming in con- 
 nection with the working of towers is the continuous oxy- 
 dation of a not insignificant quantity of the sulphurous acid 
 into sulphuric acid, not only lost to the process, but also 
 coating the limestones with almost insoluble sulphate of 
 lime (gyps), which prevents the further action of the sul- 
 phurous acid. In consequence of all these circumstances 
 these solutions come out unevenly and of ten weak, especially 
 in summer, and as corrections cannot well be made while 
 the work is going on, the trouble of clearing the tower is in 
 such cases unavoidable. In the second method, based up- 
 on limestone (battery with compressor) the difficulties 
 caused by the regulation of the draft in the tower, are sure- 
 ly dispensed with, but the other mentioned troubles es- 
 pecially the coating with gyps and the clogging with mud, 
 are still retained and to this is added the expense of setting 
 up and maintaining the compressor pump needed to force 
 through the sulphuric acid gas. Another shortcoming, 
 common to both apparatuses must be considered, that in 
 consequence of their very arrangement for continuous 
 work they always contain an excess of limestone, and 
 therefore, as long as they are in good order, i. e., as long as 
 the lime charge is not extremely coated with sulphate, they 
 yield leaches very rich in monosulphite of lime, but poor in 
 free, active sidphurous acid, which denotes itself by high 
 specific gravity with proportionally low per centage 
 in sulphurous acid. The effort to remedy this 
 by charging: the towers but partially with limestone, and 
 partially with chemically inactive porous substances, which 
 
70 THE MANUFACTURE OF CELLULOSE. 
 
 shall effect a distribution of the leach and facilitate absorp- 
 tion of the sulphurous acid; has certamtly been not alto- 
 gether without success, but has made the plant very com- 
 plicated and rather increased the other drawbacks men- 
 tioned (loss of sulphurous acid by oxydation, etc.). 
 
 When in place of the solid carbonate of lime (limestone) 
 the burned or quicklime is slacked and used in the con- 
 dition of milk of lime, a great many of the difficulties men- 
 tioned are done away with. The absorption of the sul- 
 phurous acid by caustic lime is affected much more ener- 
 getically and completely then by carbonate of lime, there- 
 fore the chances for oxydation are lesened, and secondly, 
 the apparatuses can be smaller and are more economically 
 attended to. Besides, when using caustic lime the work- 
 ing is not continuous, as when limestone is employed, one 
 has it in hand to fix and regulate as desired the amount of 
 lime in the leaches. As already mentioned, two methods 
 of circulating the gas through the milk of lime may be em- 
 ployed, i. e., drawing and forcing. Of these two methods 
 what appeared to be the most simple has been chosen, by 
 placing behind the last absorption tank an injector pro- 
 ducing a vacuum, which by its sucking action suffices to 
 keep the sulphur burning and to draw the gases formed 
 after they have passed a cooler and washer, through the 
 milk of lime. A closer examination of this method soon 
 proved some considerable deficiencies, anions them the al- 
 most enormous consumption of steam by the injectors used; 
 according to low estimates, with an apparatus producing 
 25-30 cubic meters of leach per day, the consumption of 
 steam is equal to that of a 30 horse power engine; a second, 
 still more essential failing in drawing the gases is, that the 
 saturation of the leach with sulphurous acid is thereby 
 possible in but a limited measure. Because low pressure 
 will exist in this apparatus, the liquid contained therein 
 takes up less sulphuric acid than when saturated with the 
 gas under full atmospheric presure, just as in a glass of 
 seltzer water the carbonic and gas would escape in large 
 bubbles when brought into a room under diminished pres- 
 sure. Especially during the hot summer months the leach- 
 es made by this process therefore come out very weak. The 
 full benefit of the advantages offered by working with 
 slacked lime can, however, be gained, when instead of draw- 
 ing the gases, they are forced through the liquid. Dr. 
 
THE MANUFACTURE OF CELLULOSE. 7t 
 
 Frank claims as advantages of his apparatus the following: 
 First, the apparatus makes possible, independent of out- 
 side weather conditions, the steady and uniform prepara- 
 tion of the leaches, of which inside of certain limits the 
 strength in lime as well as in sulphurous acid can be per- 
 fectly -kept under control. The strength can be raised up 
 to 10°B. Second, the plant can any time be stopped and 
 started again. Third, the mechanical power, necessary in 
 the plant is small, only five to six horse power, and for an 
 output of 30 cubic meters in twenty-four hours, but one 
 man is required per shift. Fourth, the absorption of the 
 sulphurous acid is complete and bad odors caused by es- 
 caping gas are entirely avoided, so that* the plant, requiring 
 but little space, can be put up in any locality and a special 
 building is not required. A room of 8x12 is sufficiently 
 large. Fifth, in consequence of the complete absorption 
 and the safe control of the combination of the sulphur in 
 the furnace a better use of the sulphur material is made, 
 so that by this, as well as by the rational preparation and 
 composition of the leaches, considerable saving in raw 
 materials (sulphur and lime) is gained. Formation of gyps 
 and mild settling does not occur in the apparatus. 
 6. The apparatus, of simple and solid construction, is in 
 all its parts easily overseen and easy to get at, and is with- 
 out easily destructable or sensitive parts. 7. The ap- 
 paratus, though in the first place constructed for the use 
 of sulphur, can nevertheless be used in connection with 
 pyrite furnaces. 8. The apparatus also makes it possible 
 to retain and use over again the sulphurous acid blown off 
 from the digester, without much additional cost and with- 
 out violating existing patent rights. 9. The cool water 
 required by a large sized apparatus amounts to 200-300 
 liters per minute. 10. Delay of work by sublimation or 
 clogging of the pipes is altogether excluded and all in- 
 jury to workmen as well as to the neighborhood by es- 
 caping sulphurous acid is absolutely avoided. 
 
 In regard to point 7 it may be mentioned that the author 
 was informed that the Frank apparatus could not be ad- 
 vantageously used in connection with pyrite furnaces, be- 
 cause the gases coming from pyrite furnaces are poorer in 
 sulphurous acid and richer in oxygen and because in a 
 solution of bi-sulphite, oxidation is going on quicker, and 
 considerable deposition of sulphate of lime takes place in 
 
72 
 
 THE MANUFACTURE OP CELLULOSE. 
 
 the lime milk tanks. On account of direct assistance from 
 Ben- D. Frank, the author is able to give the following de- 
 scription of his apparatus: 
 
 The plan of Frank's leading apparatus can be seen in 
 figs. 38 and 39. By means of the air pump B, which mav 
 be worked by water or steam power and which is provided 
 with the air chamber C, the air necessary for the combus- 
 tion of the sulphur, is forced into the well closed sulphur 
 furnace A, in such exactly measured quantities that gases 
 of high grading, rich in sulphurous acid, are obtained. Be- 
 cause the furnace itself as well as the cooler D and the 
 dust chamber E, arranged in the back, axe kept cool and as 
 the supply and distribution of the air in the furnace 
 
 A 
 
 Fig. 38. 
 
 done in a peculiar manner, which 
 
 y//////////y///MW4. 
 
 also make 
 entirely secure the burning of any evaporated sulphur, 
 sublimation of the sulphur and clogging of the cool- 
 ing pipes can never occur. From the dust chamber 
 E the gases then go to the cooling coil F, surrounded by 
 water, which in order to make the consumption of water 
 as small as possible are constructed according to the coun- 
 ter current principle. From there the gases go to the 
 small washer 1, in which the small residue of sulphurous 
 acid gas is retained. The cooled and purified gases then en- 
 ter the absorption battery, composed of three vessels. These 
 three vessels are placed one above the other in such man- 
 ner that the gases first pass through the solution in tank 
 2, the one most saturated with sulphurous acid and are 
 by the adding of water diluted to the required strength. 
 Then they enter tank 3, filled with a stronger milk of lime 
 and lastly the uppermost tank 4, charged with fresh milk of 
 
THE MANUFACTURE OP CELLULOSE. 
 
 :z 
 
 lime. Basins 2 and 3 are tightly covered so that the gases 
 can be forced through. Basin 4 may be covered, but as the 
 last traces of sulphurous acid gas entering in there are 
 rapidly and completely absorbed, it is generally left open, 
 because trouble from escaping gas does not occur. 
 
 When the leach has become thoroughly saturated with 
 the sulphurous acid, which can be determined in three 
 minutes by a sample taken any time during work, the 
 sulphur burning in furnace A is put out by simply stop- 
 ping the air from the compressor and thus ceasing at once 
 
 Fig. 39. 
 
 all evolution of sulphurous acid, of which also nothing can 
 go back into the room, because the furnace is closed. The 
 finished leach in tank 2 is then run out and from tank 3 
 the concentrated half finished milk of lime is let over 
 through a pipe in the bottom, closed by a valve, and water 
 is added. Into the emptied tank 3 the leach from tank is 
 then run over and the latter is filled again with fresh 
 strong milk of lime, which has been previously prepared 
 in a box arranged above tank 4 from a measured quantity 
 of burned lime. The whole operation of emptying and 
 filling over does not require over 30 minutes. When this 
 is done, the furnace, meanwhile thoroughly cooled off, is 
 
74 THE MANUFACTURE OF CELLULOSE. 
 
 opened and again charged with, a weighed quantity of sul- 
 phur, and after this has been ignited, the operation 
 is started again by reversing the air pump. According to 
 the size of the different parts of the apparatus, which can 
 be exactly calculated in advance, 10 to 20 cubic meters of 
 leach can be finished in one operation and as the time re- 
 quired by one operation, including all side work, as feed- 
 ing of the furnace and filling over of the .tanks, does not 
 exceed seven hours, the capacity of a small sized apparatus 
 is about 30 to 35 cubic meters per double' shift and of a 
 large one about 54 to 60 c. m., whereby the labor of the 
 attention, besides controlling the burning of the sulphur in 
 the furnace, is limited to the opening and closing of some 
 valves and slaking of lime, which occurs about three 
 times every double shift. 
 
 To arrange the apparatus for continuous working, i. e., 
 with continuous discharge of leach and charging with 
 fresh milk of lime, is certainly also' easy, but W. Frank 
 gives decided preference to the intermittent method here 
 described, in which the charge of the large tank is al- 
 ways finished and discharged at once, because in this way 
 the exact control of the process, especially of the proper 
 composition of the leach, is much safer. The strength of 
 the gases in the sulphur furnace can also be by this 
 method exactly adapted to the existing requirements by 
 regulating the air pump. 
 
 With Frank's apparatus sulphite leach can be prepared 
 from lime, dolomite, pure magnesia, and also, from soda, 
 in any strength up to 10° B and perfect, considering the 
 circumstance, that the leaches made with it from lime 
 cannot deposit monosulphate (gyps.) in the digester. 
 
 W. Frank's remarks about the disadvantages of the 
 towers, which are quite correct, cannot, however, be con- 
 sidered right in regard to the Kellner process. Mitscherlich 
 has at the same time used his towers for aspirators. But 
 the aspirating effect is continuously influenced and with 
 bad effect by changes in the specific: gravity of the outside 
 air (change of temperature, etc.) as well as by the con- 
 tinuous changing of the exposed surfaces of the limestones 
 and of the water, drizzling down. The gases also, must 
 enter the tower with high temperature, because otherwise 
 there would exist no difference in weight between the al- 
 ready heavy sulphurous acid and the outer air, or in other 
 
THE MANUFACTURE OF CELLULOSE. 75 
 
 words, no draft would exist. These disturbing factors are 
 avoided by Kellner in such manner that; 1, the sulphurous 
 acid is much cooled down; 2, thegases are pressed forward 
 under low pressure through the chambers or towers or 
 tanks filled with limestone. Entire independence of the 
 variations noted is thus gained and a series of absorption 
 apparatuses, as long as desirable, can be connected, so that 
 a perfect absorption of the sulphurous acid can be se- 
 cured. By this means it is just as easy to regulate the 
 proportion of the sulphurous acid tc the lime or in other 
 words, of the free and combined sulphurous acid, by filling 
 part of the absorption apparatus not with 'limestones, but 
 with an indifferent material, like pieces of brick, pebble- 
 stones, etc., and consequently the bisulphite solution ob- 
 tained from the limestones, 5s enriched with as much 
 sulphurous acid as deemed desirable. 
 
 The exhausting of the sulphur, according to the simple 
 method reported by Dr. Frank in the Papier Zeitung, is 
 determined by measuring the produced leach and tit- 
 rating for sulphurous acid with iodine. As one per 
 cent sulphurous acid corresponds to the 10 kilograms 
 contained in the cubic meter, and one part of chemically 
 pure sulphur in complete combustion yields, two parts of 
 sulphurous acid, theoretically 5 kilograms of pure sulphur 
 should yield 10 kilograms of sulphurous acid; however, the 
 second quality sulphur used in most factories generally 
 contains but 98 per cent and as on account of moisture 
 in the air used in combustion, the formation of small quan- 
 tities of sulphurous acid is never entirely excluded, and 
 when discharging and filling over small losses of leach can- 
 not be avoided, Dr. Frank guarantees 95 per cent consum- 
 mation of the sulphur charged to the furnace, so that of 
 100 kilo sulphur, weighed and charged to the furnace, 190 
 kilo effective gaseous sulphurous acid in the leaches are 
 obtained. That in careful working a higher result may 
 be obtained, is shown by the results from the factory of 
 J. Spiro & Son in Bohmisch — Krumau, published by 
 Kymmene Brack, according to which the exhaustion of 
 sulphur reaches 96.8-97 per cent; consequently from 100 
 kilo of sulphur 193 6-194 kilo of sulphurous acid were pro- 
 duced. 
 
 Regarding the composition of leaches produced with 
 Frank's aparatus already mentioned, Dr. Frank has, on the 
 
7fi THE MANUFACTURE OF CELLULOSE. 
 
 basis of scientific investigation, which have been more fully 
 confirmed by results obtained by working on a large scale, 
 secured the taking of the percentage of lime in the leach as 
 low as possible, as the main effect depends on the free ac- 
 tive sulphurous acid only, while a high percentage' of lime 
 besides other uncertainties, requires unnecessary con- 
 sumption of sulphurous acid, i. e., of sulphur material. 
 In proof of this, Dr. Frank quotes the following example: 
 A factory leach A of 7°B contained, total sulphurous acid, 
 4.35; of this, free acid, 2.35; of combined acid, 2.00; and 
 lime corresponding to the latter, 1.75. 
 
 A leach of nearly 5°B prepared in Dr. Frank's ap- 
 paratus, with which the boiling was effected in .exactly the 
 same time, but without formation of sulphate (gyps.) con- 
 tained: Total sulphurous acid, 3.254; of this free acid, 
 2.382; of this combined acid, 0.874; and lime correspond- 
 ing to the latter, 0.764. 
 
 It can be noticed that the leach B, regardless of its low 
 specific gravity and low percentage of total sulphurous 
 acid, is richer in free active sulphurous acid than the 
 heavy leach A, also, while the preparing of the latter in 
 Frank's apparatus requires at 95 per cent expansion about 
 23 kilos of sulphur per cubic meter leach, for the same 
 quantity of leach B but 17 kilo of sulphur are necessary, 
 so that besides the considerably higher effectiveness of all 
 apparatuses, with the rationally composed weaker leach a 
 direct saving of 6 kilos of sulphur per cubic meter leach 
 is gained. 
 
 In the further working of the material produced with 
 both leaches at the factory mentioned it has been settled 
 that the cellulose digested with the 7° leach yielded 1.85 
 per cent ashes, while the 1 one boiled with the weaker leach 
 gave but 0.36 per cent. 
 
 For the expert in the matter it need hardly be mentioned 
 that there can be no general directions in regard to the 
 composition of the leaches, suitable for every kind of 
 wood, as well as for all methods of boiling, but that such 
 must be conformed to material and process. Where the 
 steam does not enter directly into the boiler the leaches 
 do not get diluted and a weaker solution can be; worked, 
 but when the steam enters directly, especially when it is 
 not sufficiently dry, weak and dilute leaches are caused. 
 So for instance at the factory in Kruman with digesters 
 
THE MANUFACTURE OF CELLULOSE. 77 
 
 according to the Mitscherlich system a leach of, total sul- 
 phurous acid, 3.035: of which free acid, 2.023; of which 
 combined acid, 1.012, and lime corresponding to the lat- 
 ter, 0.827, for which but 16 kilos of sulphur per cubic 
 meter were necesary, has proved entirely sufficient. 
 
 Against the 7° leach, mentioned above, a saving of 60 
 marks per day would result at a daily consumption of 
 about 80 cubic meter leach. 
 
 Quite a large number of Frank's apparatuses have been 
 in use some years, in connection with different systems of 
 digesting. 
 
 According to information from the machine works of 
 Golzern the price for one leaching aparatus of 50 cubic 
 meter daily capacity, completely mounted, put in working 
 order and delivered with reference to the exhausting of the 
 sulphur, as guaranteed, is about 24,000 marks, inclusive of 
 license and mounting. The daily production of 50 cubic 
 meters of leach of 3.3 per cent sulphurous acid and 1 per 
 cent lime costs: 
 
 For 870 kilos sulphur at 11.00 marks per 100 kilos, 95.70 
 For 550 kilos burned lime (including loss in slak- 
 ing) at 1.50 marks per 100 kilos 8.25 
 
 Wages for 2 shifts at 2.50 marks 5.00 
 
 Power of 5 to 6 horse (if not furnished by water 
 motor) at 2.5 kilos cost per hour and horse-power 
 
 calculated per ICO kilon at 1.50 marks 6.00 
 
 Lifting of 200 to 300 liter cool water per minute, 
 
 light, lubricants, etc 5.00 
 
 5 per cent, interest, 10 per cent, amortization of 
 
 24,000.00 marks per day : 12.00 
 
 M132.00 
 
 or 264 marks per cubic meter. 
 
 Besides the low cost of production, the special ad- 
 vantage is gained, against the use of pyrite, that the 
 working of the aparatus can be started and stopped at any 
 moment, and the accummulation of the residue pyrite, so 
 annoying in many factories, is done away with. 
 
 The method of Dr. Frank has in recent years on account 
 of its advantages come more and more into use because the 
 making of leaches with it is in fact very clean, handy and 
 uniform, and entirely independent of the season. As figs. 
 38 and 39 will show the arrangement of the Frank plant, 
 
7S 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 but da not give a distinct picture of the form of the 
 sulphur furnace proper, two cuts, fig. 40 and 41, have 
 been added. It can be seen that the sulphur furnace has 
 the shape of a flat tube, with both ends made of east iron, 
 the level bottom almost entirely taken up by the low sul- 
 phur pan S. The sulphur to be. burned, previously 
 weighted, is put in the pan through the doer T, there 
 spread, and lighted by means of a red hot iron bar. The 
 
 r 
 
 FIG. 40. 
 
 FIG. 41. 
 
 right state of combustion can at any time be closely con- 
 trolled through the hole 1 in the door, covered with a 
 strong plate of glass. When the flame is burning deep 
 blue, all is in good order, but if by evaporating sulphur 
 colored yellowish-brown, more air must be admitted. The 
 supply of air and the regulating is done through the two 
 pipes rl and rS, which may be totally or partially closed 
 by valves. In order that the air may come in close contact 
 with burning sulphur at the rear end of the furnace a par- 
 tition W reaches from the ceiling down near to the pan, 
 so that the air together with the evolved gas must strike 
 close over the pan before it leaves the furnace at C and is 
 carried away, as 1 already described. 
 In comparison with the pyrite furnaces, which produces 
 
THE MANUFACTURE OF CELLULOSE. 79 
 
 gases of only about 8 per cent, the sulphur furnaces works 
 considerably better, because, as already mentioned, the air 
 supply a n be exactly measured and gases of up to 15 per 
 cent can be produced. 
 
 The leach plant of Frank's differs from a pyrite furnace 
 plant not only in the absence of the pungent smelling 
 sulphurous acid, but also in avoiding all radiation of heat. 
 This is attained by placing the entire retort inside of a 
 large box, K, of sheet iron, near the bottom of which cold 
 water is continuously running in at e, surrounding the re- 
 tort and cooling it and running off again as warm water 
 at the topi at a. In this manner it is not only much more 
 pleasant to stay in a factory with one or more Frank ap- 
 paratuses, but at the same time all annoyance to the neigh- 
 borhood, as well as therefrom resulting damage suits are 
 done away with. 
 
 In most of the sulphur furnaces of this system in use 
 about 1,500 kilos of sulphur can be burned in 24 hours. 
 This quantity is sufficient for most factories, but it is ad- 
 visable to have a complete apparatus in reserve so that 
 in case of any irregularities it does not become necessary 
 to stop the operating of the whole plant. At times, when 
 the apparatus is not in use, it can advantageously be other- 
 wise employed. Thus the tanks may be fitted with milk of 
 lime, the excess of sulphurous acid in the digester blown 
 into them, and so not a small quantity of leach of various 
 strengths is easily obtained. 
 
 Some variation from the already described methods and 
 a similiarity with the Douglas process is marked in the 
 system of leach making by the Englishman, Edward 
 Partington, whose process is explained as follows: This in- 
 vention relates to the manufacture of sulphurous acid and 
 its combinations by a continuous process, the essential of 
 which is that the water or the alkaline solution enters by 
 gravity from one tank into another, while gaseous sul- 
 phurous acid at the same time is circulating in an opposite 
 direction successively through the water or alkaline solu- 
 tion in .each receiver, while the water or alkaline solution 
 is kept in constant motion, by a rotating stirring arrange- 
 ment. In the accompanying fig. 42, three receivers A, Al, 
 and A2 are shown, while at the cover as well as at the 
 bottom are in connection with each other for a purpose 
 later on explained. Each of the receivers, which are made 
 
80 THE MANUFACTURE OF CELLULOSE. 
 
 of wood or any other material suitable for the manufac- 
 ture of sulphurous acid, or sulphites and bisulphites of 
 the alkalines and alkaline 'earths, consist of a cover a, the 
 bottom al and the sides a2, the latter being cylindrical. 
 The side walls of every cylinder carry the traverse© b (fig. 
 42), to' which are fastened the stands bl bearing the shaft 
 b2, with fixed and loose pulley, to drive by belt. At one 
 end of the shaft b2 is the bevelled gear b4, driving the 
 wheel b5 on the shaft b6, going through the stuffing box 
 b7, fixed to the cover a, into' the tank. The shaft b6 is 
 held at its upper end by a frame and reaches almost to the 
 bottom of tank Al. It is provided with the bars d, con- 
 nected by the cross bars dl, forming together with the 
 shaft a stirring arrangement by which the liquid in space 
 B of the tank can be stirred about. 
 
 The liquid for making the sulphurous acid can be either 
 water, or any solution containing a substance which can 
 with sulphurous acid form sulphites or bisulphites. For 
 the present case calcium hydrate is supposed which enters 
 the tank A near its cover through the pipe e. The tank 
 Al connected by the pipes el, e2; the pipe el leads from the 
 bottom in A below the cover of Al, while pipe e2 goes 
 from the cover of A to the bottom of the tank Al — Al is 
 connected with A2 in similar manner by the pipes ©3 and 
 el, of which e3 leads from the bottom of tank Al below 
 the cover of A2 and el reversed. The tank A2 is in the 
 same manner provided with the pipes e6 and e7, which 
 are shown broken off in the sketch, to connect another 
 tank in the same manner. The pipes el and e3 are pro- 
 vided with valves, by which the connection between the 
 tanks is broken. When beginning work, the valves are 
 closed, whereupon the liquid is run into tank A through 
 pipe e. In practice it is preferable to have the liquid con- 
 stantly run in during the operation, so that it runs from 
 A through the pipe e2 into Al, from Al through e4 into A2 
 and from A2 through e7 out. By the gravity of the liquid 
 a constant flow through the tank is thus maintained and 
 a current of sulphurous acid is drawn in the opposite direc- 
 tion through the liquid by means of an exhauster, not vis- 
 ible in the sketch, connected to tank A by pipe f3. The 
 gas is first admitted through the pipe f to the inner or 
 space B of the tank A2, where it enters into two places at 
 the bottom and goes from space B through pipe fl into space 
 
THE MANUFACTURE OF CELLULOSE. 
 
 81 
 
 B of tank A', from there through pipe f2 into space B of 
 tank A and is drawn out through pipe f3. During the pro- 
 cess gases and liquid are well mixed by the stirring ar- 
 rangement, which can be driven by the arrangemenit de- 
 
 scribed or in any other suitable manner. The liquid 
 transformed into sulphurous acid or sulphite or bi-sul- 
 phite flows from tank A2 through the outlet pipe e7 and 
 is then ready for use. The finished leach runs into four- 
 
82 THE MANUFACTURE OF CELLULOSE. 
 
 air tight storage tanks, 10x10x8, and is from there pumped 
 to the digesters. 
 
 In Partington's factory the sulphurous acid is produced 
 in a sulphur furnace of 2x8, by burning of pure' regener- 
 ated sulphur of 99 pier cent, and of pyrite (with 48 per 
 cent, sulphur) and it first circulates through a system of 
 pipes, cooled with waiter, before it is permitted to enter 
 near the bottom of the lowest tank. 
 
 After the preparing of leaches, as performed according 
 to the methods, mostly employed in Germany and Eng- 
 land, has been fully described, some other methods;, as 
 given by Professor Hoyer in his book, shall for the sake 
 of completeness be shortly treated in this chapter. 
 
 Eckman uses as leach a solution of sulphite of magne- 
 sia, which contains two equivalents of sulphurous acid 
 for one equivalent of magnesia and in such concentration 
 that almost 1.4 per cent magnesia and 4.4 per cent sul- 
 phurous acid are present in it. To prepare the sulphite, 
 Grecian or German magnesite is calcined in lime kilns, 
 then in towers of lead (with inside wood lining to protect 
 the lead) exposed to' sulphurous acid, produced from sul- 
 phur and to water drizzling down and finally discharged 
 as sulphite solution. 
 
 In the process of Franke in (Sweden) & solution of acid 
 sulphite of lime is emlp'oyed, made by leading hot sul- 
 phurous; acid, produced by roasting pyrite in a tower 
 13 meters high, divided into' several vertical chambers, 
 which are filled with limestones and which can be charged 
 and attended to independently of each other, and to which 
 water is admitted from above in quantities just sufficient, 
 so as to secure a warm solution, at once ready for use. The 
 solution is run into receivers' otf cement, lined with lead 
 and from there it is. pumped to the digester. 
 
 In the method of Graham in London, at first only the 
 solution of the monosulphites of any base (potash, soda., 
 magnesia) is charged into the digester and after it has 
 been freed from air and carbonic acid, the effective com- 
 bination is produced by pumping in sulphurous acid gas 
 or solution. In this method, which is effected in a ver- 
 tical digester with steam jacket, the escape of acid is pre^ 
 vented in the 1 first place, out the liquid is steadily main- 
 tained in equal strength by filling up from the bottom, 
 when necessary. 
 
THE MANUFACTURE OF CELLULOSE. 83 
 
 The method of Picket in Lausanne, (D. E. P. 25331) is 
 based on the theory that in consequence of the high tem- 
 perature now generally used, the gums and resins in the 
 wood are changed into tar and thus render so difficult the 
 bleaching of the product that it is practical to employ a 
 solution of sulphurous acid, which would disolve the in- 
 crusting substances at a lower temperature. For this 
 purpose Picket recommends an aqueous solution of sul- 
 phurous acid. But as 100-500 grams of sulphurous acid 
 have to he dissolved in 1 liter of water to obtain a pre* 
 sure of from 5-7 atmospheres at a temperature of 80- 
 90° C in the digester, liquid sulphurous acid anhydride is 
 charged into the digester under pressure under the above 
 mentioned conditions. The ac:d mixes with the water and 
 yields the desirfd solution, which in the digester by steam 
 evils is raised to the the temperature of not over 85 °C, be 
 cause at 90° C carbonization would begin. To make the 
 liquid thoroughly penetrating, it is recommended to pro- 
 duce a vacuum before it is charged to the digester, to open 
 the pores of the wood. 
 
 The agueous solution prepared according to this method 
 (without alkali) contains about 1 1-2 to 2 per cent of sul- 
 phurous acid. When the necessary quantity of this acid 
 together with the w r ood is charged into the digester, in 
 another boiler a liquid of the same kind is heated to about 
 100° and the sulphurous acid thus set free is driven over 
 to the digester until the leach in there contains 2 per 
 cent acid. After the operation is finished, the acid is 
 driven off in the same manner and used for the preparation 
 of new leaches. The highest temperature employed is 
 105 °C. The essential ditference of this method in com- 
 parison with other sulphite processes is therefore, that no 
 lime is contained in the solution, while a small per centage 
 is really necessary in order to neutralize the sulphuric acid, 
 which forms. The resulting product is less white than 
 with other methods. 
 
 According to Flodgnist in Gothenburg, in preparing the 
 digesting liquid, the sulphurous acid is partially led over 
 limestone, partially over bones-, the fat of which has been 
 extracted, which are piled up in towers or chambers, to 
 form a mixture of sulphite and phosphate of lime and be- 
 sides to produce glue material for the manufacture of glue, 
 wdierefore always several chambers (as already mentioned, 
 
84 THE MANUFACTURE OF CELLULOSE. 
 
 as many as 10) are in use, so that one after the other can 
 be disconnected for discharging and refilling, as necessary. 
 
 The method of Archibold in Oswego, is based on the 
 principle to produce sulphite of lime directly upon the 
 fibre, in order to make it thus a,ct so much more power- 
 fully. To this purpose the raw materia i. e., the dressed 
 wood, is first saturated in the digestef /ith milk of lime, 
 which consists of from 1 to 6 parts of lime in 100 parts of 
 water, and for hard wood, also 1 part of nitrate of lime. 
 Then sulphurous acid (either in gaseous or in liquid form) 
 is charged, to the digester and after about five minutes it is 
 exposed to a pressure of from 4 to 5 atmospheres and some- 
 times,, according to the kind of wood, for one to two hours 
 and a half 
 
 At the end of this chapter about leaches and leach- 
 making in regard to sulphite leaches it must be mentioned 
 again, that measuring the concentration with the areo- 
 meter, in use in most factories, does, not give a correct re- 
 sult, and to the advantage of the digesting operation it is 
 highly desirable that the leaches be tested every time before 
 using, by analysis, for their strength in active sulphurous 
 acid. This is possible without a complete laboratory out- 
 fit, by the following method of Dr. E. Hoehn, based on the 
 reaction of iodine on sulphurous acid under decomposition 
 of water, forming hyclroiodic acid on the one side, and 
 sulphuric acid on the other. When therefore a solution of 
 pure sulphurous acid is extricated and to this for instance 
 10 cubic-centimeters one-tenth normal iodine had to be 
 used, at the end of the reaction the liquid will contain a 
 certain quantity of hydroiodic acid, corresponding to 10 
 cubic-centimeters one-tenth normal-iodine, and an equal 
 amount of sulphuric acid, so that in neutralizing the acid 
 formed by an alkali, 20 cubic-centimeters one-tenth nor- 
 mal-soda will be necessary. But in place of uncombined 
 free sulphurous acid in the solution to be tested, there is 
 an acid sulphite, for instance, of lime, the same amount of 
 sulphuric acid is formed in the titration, but which will 
 be partially neutralized by the base already existing, so that 
 in titrating back the two acids formed, the double amount 
 of cubic-centimeters of iodine is not necessary, but much 
 less suffices. 
 
 SODA PEOCESiS. 
 
 It lies in the nature of the soda process, because the so- 
 
THE MANUFACTURE OF CELLULOSE. 85 
 
 da employed therein, like the alkalis in general, does not 
 attack iron, that the boilers used in manufacturing soda- 
 cellulose can be more simple, than the sulphite-digesters, 
 which latter must be fitted with all possible appliances for 
 protection. According to the method of working, they 
 may have small or large dimensions, may be fixed or rotat- 
 ing, placed horizontal or vertical. In most instances fixed 
 vertical boilers are used, because the process of boiling 
 mostly takes place with circulation of the leach and a 
 more effective stirring up is not absolutely necessary on 
 account of the very large dimensions and weights of some 
 of these digesters, it would be both difficult and expensive 
 to make them of the rotary pattern. 
 
 The manufacture of soda-cellulose is really not a new 
 invention, but only a modification of the method used in 
 the manufacture of straw-stuff, as the wood is boiled with 
 soda lye under pressure in a similar manner. It is twenty- 
 five years since the present Commercien-rath Herr Max 
 Dresel in Dalbke, Grermany, took upon himself this task 
 of perfecting this process, and the author may be per- 
 mitted to give here, according to the personal notes by 
 Herr Dresel, a brief description of the details and results 
 of the experiments, made 1871. First of all, in 1870, he 
 acquired from the engineer ,James A. Lee, the rights and 
 models for a chopping machine, which was previously 
 built after a dye-wood chopper by Houghton in Manches- 
 ter for the Cone paper mills in England. This Mr. Lee 
 had at the time a small machine factory adjoining the 
 Cone mills, near Sidney, England, and was engaged by 
 contract to repair and superintend the mechanical plant. 
 In this capacity he undertook a small change in the Hough- 
 ton wood-cutter and then had the whole machine patented. 
 The Cone mills, in 1870, were working with very primitive 
 apparatus, part of which had been designed by the engineer 
 Houghton, part of which was built after that used by Jes- 
 sup & Moore ,in Philadelphia, for the boiling of straw and 
 poplar wood, producing very imperfect brown half-cellu- 
 lose, which they were not able to bleach and which could 
 be only employed for brown packing paper. On a voyage, 
 undertaken in 1870, to England, Herr Dresel, while not 
 allowed to inspect the Cone mills, found out that the 
 boilers used in this factory for boiling straw and wood 
 were designed by Mr. Houghton, who held a patent on 
 
86 THE MANUFACTURE OF CELLULOSE. 
 
 them. These boilers were horizontal cylinders, lined with 
 a large system of pipes and the boilers themselves lay in 
 the open fire. This pipe system was fed with water, thus 
 heating the contents of the boiler. 
 
 In France, by the courtesy of the paper manufacturer, 
 Dambricourt, in St. Omer, he examined a large straw 
 boiler, which lay in direct fire, and had a large stirring 
 arrangement inside, in which poplar wood was being boiled 
 experimentally. According to the observations there made 
 Herr Dresel concluded that, when with a boiler with di- 
 rect firing, without a stirring inside, as in the Cone mills, 
 poplar wood could be boiled, and when this was also pos- 
 sible, as in St. Omer, with direct heating in a horizontal 
 cylindrical boiler with stirrer, it would also be possible to 
 boil wood in a horizontal cylindrical boiler with direct fire 
 and without inside stirring arrangement. 
 
 After wearisome trials he succeeded in finding a pro- 
 cess of boiling with caustic soda in a small experimental 
 boiler, which promised to answer also on a large scale for 
 the dissolution of fir, and especially of pine wood. He 
 then ordered a boiler forty-five feet long and four feet in 
 diameter, designed for ten atmospheres practical pressure. 
 After a complete plant had been finished, the large wood 
 digester was put to work on October 1, 1871, and thus the 
 first wood fibre factory on the continent was opened. To 
 procure a practical scaling arrangement, which could stand 
 the necessary high pressure, caused especial difficulties, but 
 it should be considered, that in the beginning any leading 
 points and examples for the preparing of leaches on a 
 large scale, as well as for the duration of the process of 
 digesting and all other occurrences were unobtainable, and 
 consequently the first period of manufacturing caused con- 
 siderable expenses. So much greater was the satisfaction 
 then, when the results of the operations were yielding a 
 product, capable of being bleached, which in many in- 
 stances could serve as substitute for rag fibre in the manu- 
 facture of paper. The ideas worked out and tried prac- 
 tically in the first Dalbke factory, were taken up by the 
 above-mentioned Mr. Lee, and by the engineer, Eosenham, 
 employed by the Braekwede boiler works, and later intro- 
 duced in Sweden under the name of the Lee system. 
 
 Regarding the process of digesting itself, a soda-leach 
 of ten degreesB, a temperature of 360 degrees F., and a 
 
THE MANUFACTURE OF CELLULOSE. 
 
 S7 
 
 pressure of from nine co ten atm spheres proved most sat- 
 isfactory. The boiler contained 01 rather yielded 850 kilo- 
 gramme of dry stuff. 
 
 After the first large digester had been in working for 
 a longer period, a number of disadvantages were experi- 
 enced with it, which were principally that with the inter- 
 mittent use, the sudden change between strong heating 
 and cooling off caused leaks in the seams of the boiler, 
 which could not be wholly avoided and, not considering 
 the large expense for repairing, caused heavy losses in 
 leach. There was also a very unsatisfactory use of the 
 
 Fig 44. 
 
 fuel with this boiler, and the cost of heating was thus out 
 of proportion. Finally the cooling off could be effected 
 but slowly and only with loss of leach. For this reason, 
 Herr Dresel has after much experimenting devised the 
 construction, which has been patented to him under Fo. 
 5,891, in May, 1878, which is based on the principle of 
 heating the digester without exposing it to the fire. This 
 is done by direct heating, but without vapors and without 
 dilutionof the leach, by the automatic circulation of the 
 leach, which may be brought to high pressure at will. 
 Later on he improved this construction, and in 1878 he 
 
88 THE MANUFACTURE OP CELLULOSE. 
 
 took out a supplementary patent, which principally con- 
 cerned improvements in the pipe-heating system. The 
 following figures show the perfected construction: The up- 
 right cylindrical digester A, which is funnel-shaped below, 
 has at the lower side a manhole for discharging and on top 
 a wide fillhole with cover. In the middle of the lower 
 bottom there is a nipple which is directly connected with 
 the heating apparatus B, and also, if desired, with other 
 boilers. This connection may be opened or closed, as re- 
 quired, by cocks or valves. 
 
 The heater B, directly connected with the boiler, con- 
 
 4£fe* 
 
 Fig. 45. 
 
 sists of a system of pipes B. lying parallel either side by side 
 or one above the other, at certain distances and with a cer- 
 tain inclination, which end in the narrow chambers K. 
 
 The liquid with which the digester is filled enters the 
 lower chamber at one side, while the heated liquid ascends 
 from the upper chamber at the other side, so that the 
 liquid in entering the heating apparatus fills all pipes at 
 the same time. 
 
 The liquid, which is quickly heated on account of the 
 large heating surface, rises from the heating apparatuswnto 
 the pipe, discharging into the boiler at its upper end and, 
 circulating through the digester, returns into the lower 
 
THE MANUFACTURE OF CELLULOSE. 89 
 
 heating pipe chamber. In this manner an automatic cir- 
 culation of the liquid takes place, and the contents of the 
 digester can thus be heated by direct fire, without expos- 
 ing the apparatus itself to the fire. By this arrangement a 
 more rapid heating, energetic and even circulation in the 
 digester is secured with almost no formation of steam. 
 There is also a more perfect impregnation and more rapid 
 heating of the contents of the digester, as compared with 
 a heating apparatus formed by a horizontal coil, as design- 
 ed in the main patent. 
 
 These cellulose digesters have proved very successful, 
 and three of them have been at work since 1877, without 
 one of them having to be repaired. Moreover, these boil- 
 ers yield a very good product, are charged and discharged 
 with ease, and have the great advantage of absolute safety 
 and comparative cheapness. 
 
 With these patent digesters there is also the advantage 
 that with them the operation can be finished in from two 
 and one-half to three hours, and that the stuff can be 
 washed in them without damage to the digester and with- 
 out loss of material; further, on account of the energetic 
 circulation, a uniform and complete solution of the in- 
 crustations is effected, which is proved by the fact that 
 the cellulose made in them can be bleached white with 
 from 8 to 9 per cent chloride of lime, while the other soda- 
 cellulose require 12 and sometimes even 20 per cent of 
 chloride of lime. The boilers are used for soda, as well as 
 for sulphite-leaches, which in evaporating furnaces con- 
 structed by Herr Dresel are evaporated and then calcined 
 in the so-called calcining furnace. 
 
 In an American factory the digesters have 1.5 metres 
 diameter and 5 metres height. Inside there is a perforated 
 false bottom and cover, which arrangement is provided in 
 most boilers of this kind so that the wood cannot stop up 
 the tubes, but is retained in the middle large space. The 
 soda-leach has a strength of 12 degrees Beaumi and by direct 
 fire it is gradually raised to the boiling point and the pro- 
 cess is finished at a pressure of from six to eight atmos- 
 pheres (160 to 172 degrees C.) in about six hours. Dahl, 
 in whose process for 100 kilos of medium dry wood about 
 26 kilos of the salts are necessary, as, mentioned in the 
 chapter of leach-making, corresponding to a leach of from 
 
90 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 six to fourteen degrees Beaumi, also boils in iron digesters 
 with a pressure of from 5 to 10 atmospheres, and indeed 
 from 30 to 40 hours. In order to obtain a good circulation 
 in the digesters and still avoid direct firing, Koerting, in 
 Hanover, who makes injectors a specialty, has used an in- 
 
 FIG. 
 
 jector with a digester illustrated in Hover's work, page 
 190. Figure 46 shows this boiler: B is perforated bottom 
 in the boiler A, which is built cylindrical with rounded 
 
THE MANUFACTURE OF CELLULOSE. 91 
 
 ends. The manhole C, serves to fill in the wood and the 
 discharging is done by an opening above the bottom, not 
 visible in the sketch. Alongside the boiler is a stand-pipe 
 F, which is connected with the steam pipe D, and also by 
 branch pipes with the lower and upper part of the digester 
 which at E are connected by the well-known Koerting in- 
 jector. The steam coming to the boiler through D draws 
 by means of the injector E the leach accumulated under 
 the bottom B through pipe r, forces it through the stand- 
 pipe F into the upper part of the digester and thus not 
 only effects proper heating, but also a lively circulation of 
 the leach, which, after the finish and after shutting off 
 the steam supply is let off through the pipe s. 
 
 For starting and maintaining the circulation of the leach 
 it is only necessary that the pressure of the steam supply 
 be by one atmosphere higher than the pressure in the di- 
 gester. To regulate these conditions of pressure, which 
 can be observed by a manometer M, a safety valve is ar- 
 ranged at C, which is weighted in proportion to the press- 
 ure required in the digester. 
 
 The system of Ungerer in Vienna, already mentioned as 
 the most rational soda process for the best utilization of 
 the leach, is described in regard to the digesting process 
 by Hoyer as follows: The method is based on the prin- 
 ciple of displacement and the work is done in such man- 
 ner that the leach in certain order passes a number of di- 
 gesters (Battery), which are heated by steam and charged 
 with wood cut into thin slices. A battery consists of 7 
 to 10 upright, fixed digesters, which by pipes and valves 
 are connected in such manner that steam or leach can be 
 let from one boiler into another, as directed. With this 
 system of digesters the work is so carried on that fresh 
 wood, with the substances easiest dissolved, is first treated 
 with steam which comes from the digester which is ready 
 to be discharged, and then with leach weakest in soda, be- 
 cause richest in extractive matter, which oomes from the 
 digester, which was most recently charged with fresh 
 wood, and has, therefore, passed all the other digesters 
 and has started circulation with the boiler from which the 
 wood is next to be discharged. If, for instance, the battery 
 consists of seven boilers, A. B. C. D. E. F, Gr, in working, 
 the leach is changed about as follows: When, for instance, 
 C has been newly filled and B is to be disc'iarged, steam is 
 
92 THE MANUFACTURE OF CELLULOSE. 
 
 first let from B into C to steam the fresh wood, the weak- 
 est leach is then run from D to C and so in succession; al- 
 ways stronger, from E to D, from F to E, from G- to F. from 
 A to G- and from B to A. After about one hour the leach 
 is let off from C, to be regenerated, while immediately 
 after this discharge an advancing of the leach D to C 
 etc., takes place, and A is charged with fresh, pure leach. 
 In this manner every hour one digester is ready for dis- 
 charge and it's charge is washed with hot water under 
 steam pressure, before being emptied. In the same degree 
 in which the leach in its circulation becomes weakened, 
 also the temperature and the steam pressure can decrease;, 
 which in this process, in which the leach by the contin- 
 uous change comes to effect under the most favorable cir- 
 cumstances is in the digester, charged with fresh leach, 
 not mere than about 6 to 8 atmospheres for pine and 3 to 
 4 atmospheres for leaved wood. The fresh leach contains 
 for pine wood from 5 to 6 per cent, for leaved wood from 
 3 to 4 per cent soda. The leach saturated with the ex- 
 tractive matter and incrusts from the last digestation is 
 then by evaporation and calcination always recovered 
 again for the process, so that according to the statements 
 by the inventor, for 100 kilo dry cellulose but 5-6 kilo of 
 soda get lost. According to age, growth and kind of the 
 wood used, 1 volumeter wood yields from 100 to 120 kilo 
 cellulose for pine wood and somewhat more for leaved 
 wood (150 to 180 kilo). Further for 1 volumeter wood 
 about 60 kilo soda of 90 per cent are estimated for con- 
 version into caustic soda, of which 0.9 are recovered by 
 regeneration. 
 
 B. SULPHITE PKOCESS. 
 
 The boilers, which, are used in the sulphite process and 
 especially in the Mitscherlieh process, first to be treated, 
 differ from the previously described considerably, be- 
 cause on the inside, like all parts connected with it, 
 they must be protected against the corrosive action of the 
 sulphurous acid. Besides as the digesting process, accord- 
 ing to Mitscherlieh, requires much more time, it is a mat- 
 ter of consequence to arrive at boiling at once as much 
 wood as possible, i. e., to make the digesters very large. 
 Certainly not all factories working according to> Mitscher- 
 lieh, have horizontal boilers; some also have upright, of 
 
THE MANUFACTURE OF CELLULOSE. 
 
 92 
 
 somewhat smaller dimensions, most, however, have the 
 horizontal digesters of 4 meter inside diameter and 12 
 meter length, which hold the 'enormous quantity of a 100 
 cubic-meters of cut wood and still have to take 60 cubic- 
 meters of leach. With such dimensions it becomes neces- 
 sary to use very heavy metal, at least 18 millimeter (at the 
 half rounded heads still stronger) and also to consider the 
 expansion of such iron masses in heating. In fig. 47 and 
 48 it c an be seen that the foundation of the digesters is 
 
 3J 
 <J5' 
 
 3 
 6 
 
 formed by two strong walls, over which 5 strong beams are 
 
94 THE MANUFACTURE OF CELLULOSE. 
 
 laid; the digester has rivited to- itself five cast iron feet, 
 which rest on these beams, but not immediately, as short 
 iron rollers are between the feet and the beams, which 
 eventually permit some expansion of the long digester. 
 Two manholes on top, which by easily loosened screws can 
 be tightly closed (the packing is- done with rings of lead 
 and by means of a paste of cellulose) permit filling from 
 two sides at the same time and two- oppositely arranged 
 manholes below are for discharging, whereby after finish- 
 ing the operation all four opened manholes let the air pass 
 through and make thus some cooling off possible. It may 
 here be mentioned, that the foundation walls must be 
 above man high, so that the spa.ce formed under the di- 
 gester, which is connected and arranged for draining off, 
 will be large enough to< easily hold the whole charge of the 
 digester. The digester itself is filled as follows: 
 At one upper end is a mainvalve to shut off the digester 
 during the operation, and a, cross-nipple, carrying four oth- 
 er valves; of these a is connected with the boiler, b with a 
 water pump or a reservoir, c with the leach tank a and d 
 with the drive-over- tower. At the opposite tower end is 
 the discharge value e and besides in the middle of each 
 head a nipple leading inside:, carrying an angle thermom- 
 eter and a manometer, also a small cock, by which during 
 the operation some leach can be drawn and indirectly the 
 process and its finish can be observed and determined. 
 Either also in a head, or at the sidewalk, four more nipples 
 are arranged next to each other, through which the heat- 
 ing pipes enter the inside, each of which can be shut off 
 by a valve (f, g, h, i). 
 
 Because in the Mitscherlich process, as mentioned, the 
 boiling operation takes much longer than in the other 
 methods, the leach wo<uld become too much diluted, if the 
 steam were let directly into the boiler; also the tem- 
 perature, respecting the pressure in the boiler could not 
 be as well regulated; therefore the heating of the eon- 
 tents of the boiler is effected by a system of pipes of hard 
 lead, which about covers the lower third of the total inside 
 wall. Because it often happens, that a pipe bursts during 
 work and has to be shut out, for precaution four pipes 
 were laid alongside, which have a total length of about 000 
 meters or more. The four pipe systems., which lay in four 
 coils close to each other, pass out again at the opposite end 
 
THE MANUFACTURE OF CELLULOSE. 95 
 
 of the digester and every system can be shut off inde^ 
 pendently by a valve. This is necessary, because 1 , as already 
 mentioned, a pipe sometimes bursts inside while working. 
 When then in this coil the steam has been shut off, the 
 leach enters through the leak into this pipe and through 
 it gets outside; in such case the leak can be noticed by a 
 strong smell in the room, and closing both valves the pipe 
 system concerned can be completely shut out. By this 
 the duration of an operation is certainly somewhat pro- 
 longed, but the loss of leach and injury by the escaping 
 sulphurous acid are presented; the process can go on with- 
 out delay. 
 
 The repeatedly mentioned protection of the iron digest- 
 ers is effected as follows: The inside well cleaned digester 
 is first coated with a mixture of tar and pitch, and on top 
 of this very thin sheets of lead, so called lead foil, about 
 1-8 millimeter thick, are pasted in single sheets, sheet by 
 sheet, so that the sheets are well pressed into all cavities 
 and corners, but without tearing them. The lining is, 
 however, done piece by piece, and only as far. as the 
 brick lining is about to be laid, which is provided to form 
 the main protection. For this purpose it is necessary to select 
 quite hard, porous, acid proof, hard burned stones of the 
 form and size of the common brick, but which are made 
 with tongue and groove, in order to be able to make 
 a joint as close as possible. Because it is not so much the 
 liquid leach, which acts destructively, as the gaseous sul- 
 phurous acid, evolved in the upper part of the digester, 
 it is-most important to protect mainly the upper half of the 
 digester; it is therefore sufficient, when the lower half of 
 the boiler is well covered with two flat layers of brick, 
 while the upper as a rule consists of two vaults, each 25 
 centimeters thick, one spanned over the other, consequent- 
 ly of two roll layers. For binding, best Portland cement, 
 mixed with some sand, is used. The whole wall, especial- 
 ly the connection, to the manholes, the sides of which 
 must be protected by several heavy sheets of lead, must be 
 made very carefully, because otherwise a new digester 
 would be completely eaten up in a short time. The sul- 
 phurous acid gas under pressure eats through very quick- 
 ly, indeed, when there is but one defect joint. For this 
 reason it was tried to limit the number of joints to a 
 minimum and lately instead of the brick form, plates were 
 
SS THE MANUFACTURE OF CELLULOSE. 
 
 chosen and to make the different joints as thin as possible, 
 the form of these plates has been exactly suited to the 
 shape of the digester, which especially at the round heads 
 is of great importance. At the same time, in used burned 
 plates, which are certainly much thinner than the bricks, 
 the advantage has been gained, that the hold of the boiler 
 becomes considerable larger and the weight of the ap- 
 paratus somewhat smaller. At this point it may be men- 
 tioned that in lining the boiler, it can scarcely be prevent- 
 ed that the thin lead foil in some places gets damaged; by 
 this the so necessary protection is partially missing. For 
 this reason, lately sheet lead, 3 millimeters thick, in rolls, 
 as large and wide as possible, is employed. These are 
 soldered together inside (whereby naturally the boiler has 
 to be turned), so that a perfect lead lining protectiiigly 
 covers the sheet iron. On account of the' weight of the 
 lining alone it is necessary to connect the lead to the wall 
 of the digester with screws with large heads and then to 
 cover these heads again with plates of lead, soldered over. 
 In selecting the sheet lead care must be taken to use but 
 the best. Because in change of temperature lead contracts 
 differently from sheet iron, wrinkles are often formed in 
 it, its structure become chrystallinic and sags. In soft lead, 
 when warping, it is supposed that the pores open and ad- 
 mit foreign substance. To make possible the: employment 
 of sheets as thick as possible, only thin sorts should be 
 taken, and of these as many layers rolled together under 
 great pressure, as is necessary to obtain the desired thick- 
 ness. 
 
 All -valves, mentioned before, must certainly also' be 
 lined with lead in all their inner parts, as this metal best 
 resists sulphurous acid. It is also good precaution to ar- 
 range between steam boiler and digester a check-valve, so 
 that the leach never can. enter the boiler, should the pres- 
 sure become less than in the boiler. 
 
 The proper process of digestion comprises the follow- 
 ing details: After the lower manholes were closed and the 
 wood filled in through the upper one and distributed as 
 uniformly as possible in the digester, the two upper ones 
 are screwed down, the main valve is opened and through 
 this valve steam is let into the apparatus; as, soon as the 
 digester is all filled with it, the outlet valve' at the lower 
 end in back of the digester is opened and the steam is 
 
THE MANUFACTURE OF CELLULOSE. 97 
 
 rushed through, the wood charge for about 8 to 10 hours, 
 whereby care has to be taken that no pressure is produced 
 in the digester. The steam condensed on the wood runs 
 off as a dark-brown liquid, which smells like vanilla, from 
 which is clear, that already by steaming part of the in- 
 crusts are dissolved. But the main object of steaming is 
 to prepare the single pores of the wood for admitting the 
 leach. The steam also displaces the air from the inner 
 portions of the wood slices. As soon as the steaming is 
 finished, the outlet valve closed, the steam supply shut 
 off and the leach valve c is opened, the cold leach streams 
 into the digester, the steam condenses, a vacuum is formed 
 and each smallest pore eagerly draws in the leach, so that 
 finally not only the spaces between the wood are filled 
 with leach, but also the wood itself is thoroughly soaked 
 full with leach, like sponges, whereby is prevented the 
 rising of the wood above the level of the liquid. In this 
 manner the sulphurous acid does not only act dissolvingly 
 from outside, but also out from the inside. When the 
 digester is filled with leach so far that only a small space 
 is left at the top, so that the vapor evolved in boiling has 
 room, the valve c is closed and after all packings are tightly 
 screwed clown, the boiling itself is started, by opening all 
 four steam valves, whereby care has to be taken that the 
 pressure in the steam boiler is the highest possible so that 
 the digestion goes on energetically from the beginning and 
 the temperature from its first state of 40 to 45° C soon 
 rises to 70°, because before that chemical action of the 
 acid does not take place. The valves at the end of the 
 heating coils are left open in the start, that the condensed 
 water can run off freely and before steam comes out, 
 these are partially closed, and then altogether, when later 
 the temperature in the digester rises too high. Thus the 
 coil is gradually filling with water and it is avoided, that 
 the pressure in the digester is larger than in the coil, which 
 would be the case when the steam supply valve is closed 
 and the outlet valve left open. Formerly it had been the 
 first principle with every boiling operation that the pres- 
 sure in the digester never should exceed 3 atmospheres 
 and the temperature should not rise above 114°. When 
 these limits were reached some was driven over at once, i. 
 e., part of gaseous sulphurous acid in the digester was let 
 off into the "drive-over-tower." But competition, declin- 
 
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100 THE MANUFACTURE OF CELLULOSE. 
 
 ing prices of the cellulose, and the endeavor caused thereby 
 to produce more and more with the same plant, have in- 
 duced the manufacturer to exceed these limits, not only 
 to gain time in charging and discharging of the digester, 
 but also to shorten the operation of boiling as much as pos- 
 sible. By careful experimenting the author has found that 
 without endangering the product, 3.4 to 3.5 atmospheres 
 and temperature as high as 120° Celcius may be 
 safely applied. By this whole period of boiling, 
 which formerly required 75 to 85 hours (warming up in- 
 cluded), has by and by become reduced to 58 hours and 
 less, of which but 32 hours are required by the process 
 proper. It must be mentioned in this place, that the 
 kind of heating pipe system is of much importance in re- 
 gard to the duration of the process, as the length of the 
 pipes, the strength of its walls, keeping it free of de- 
 posits of sulphate of lime, all have an .effect in hastening 
 or delaying the delivery of heat, and also' the digesting. 
 It is well to take care that neither pressure nor temperature 
 go down before the operation is finished, but be kept uni- 
 formly high, as much as possible, at least towards the end. 
 This certainly requires sharp control. To give a clear 
 illustration of the run of the digesting process in its differ- 
 ent stages and at the same time to get acquainted with the 
 time necessary between the charges, examples from practice 
 are given on the preceding page which contain the notes 
 about any operations as written down for control in the so- 
 clled "boiling-book" of every cellulose factory. 
 
 Examining and comparing these three examples it can 
 be clearly seen that the warming up. until the beginning 
 of the digesting process requires from 18 to 28 hours 
 time and that the proper digestation in these three ex- 
 amples takes almost equally long, i. e., 31.5, 35 and 37 
 hours. The previous steaming has required 8, 10 and 12 
 hours time. The charging of wood and acid was also vary- 
 ing according to local conditions. Including these manipu- 
 lations, from charging to blowing off were required 1 , in 
 the first factory 80-| hours-, in the second 87 hours, and in 
 the third 72 hours. To this time has to be added the blow- 
 ing off, letting off the leach, cooling off and washing, also 
 discharging and revision of the boiler, to be done any 
 time, which labors require at least 18 to 24 hours, so that 
 for the total duration of one operation 90 to 100 hours 
 
THE MANUFACTURE OF CELLULOSE. 101 
 
 have to be calculated, consequently only 7 to 8 operations 
 can be made per month with one digester. 
 
 When employing sufficiently strong leaches, i. e., rich 
 in free sulphurous acid', when other circumstances are fa- 
 vorable, especially in larger works, with Mitscherlich boil- 
 ers 11 to 12 operations may be made per month, but the 
 leach must contain about two parts free sulphurous acid 
 for one part combined. 
 
 In regard to the controlling of the process and especial- 
 ly determining its end, this can be done only by drawing 
 from the stop-cock at the gauge-nipple some of the leach 
 and testing it. For this purpose a 200 mm. test tube is- 
 filled to about 60 mm. with commercial ammonia solution, 
 and holding the tube with a clamp, some of the hot leach 
 from the stop>-cock is added and then the liquids well 
 mixed. The tube is then set aside in a test tube stand. 
 The ammonia combines with part of the sulphurous acid 
 of the bisulphite of lime, whereby the resultant mono- 
 sulphite of lime becomes insoluble, separates and deposits 
 at the bottom as a white powder. The higher this layer 
 of precipitate is the more bisulphite of lime is contained 
 in the leach therefore the less it has been used up. 
 Because in practice the duration of each operation is al- 
 most the same, it is sufficient, when beginning, to take 
 samples in the second half of the process, from time to 
 time. But the less the precipitate appears the oftener the 
 tests must be made; towards the end this should be done 
 every quarter of an hour, as the precipitate must not be 
 allowed to entirely disappear. The nearer the end the 
 quicker and coarser the precipitate; its color becomes yel- 
 lowish, and smell changes, is not a pungent, and the liquid 
 becomes sticky and darker. When the precipitate appears 
 but 6 to 8 mm. high, the operation is finished and the di- 
 gester is blown off. After the water is started in the 
 drive-over tower the main valve of the digester and valve 
 d are opened, s>o that the gaseous sulphurous acid can go 
 over to the tower through a lead pipe, which for cooling 
 off is let in a coil through water. As soon as the aqueous 
 solution formed there reaches -1°B, it is run off into the 
 acid-tank. As at times a solution of from 10-12°B is ob- 
 tained, this blow-off acid is quite useful to the manufac- 
 turer; he improves with it the strength of a leach neces- 
 sary in the next operation. As soon as the pressure in 
 
102 THE MANUFACTURE OF CELLULOSE. 
 
 the digester has become reduced to one and one-third of 
 an atmosphere, which takes place in a few hours, the dis- 
 charge valve is opened and the leach, still under some pres- 
 sure, is let off through a lead pipe, at least 100 mm. in 
 diameter, into the leach basin, about which more will be 
 said later on. When the pressure in the digester is alto- 
 gether reduced and the leach run out, the discharge valve 
 is closed and the boiler filled through water valve d to 
 about one-half with cold water, during which manipula- 
 tions both upper man holes are opened. Through these, by 
 means of a pole and a small arrangement fixed to it, the 
 first real sample of the finished cellulose can now be taken 
 out to see whether the operation was a success, and ac^ 
 cordingly to make disposition for the further working of 
 it. But in case of a failure a repeated charging of acid 
 and repetition of the boiling operation would not yield 
 a better result, therefore the charge has to be taken out 
 at all hazards. 
 
 Letting in cold water is mainly for the purpose, not 
 only to somewhat cool off the hot mass and the digester 
 itself, but also to free the material from the brown leach 
 as quickly as possible, thereby giving it a preliminary 
 washing or rather, rinsing out. After this first washing is 
 let off, as second rinsing is done in the same manner, but 
 then the lower manholes are at once opened, and poles 
 are pushed through to the upper manholes, so that a 
 draft through the digester is secured and the mass is 
 cooling off as much as possible. 
 
 As soon as it can be done, two persons, mouth and 
 nose covered with sponges, must go into the digester and 
 commence discharging with wooden shovels and picks. 
 This on account of the strong smell and. great heat still 
 prevailing in the apparatus is not easy work: the labor- 
 ers must often shift and naturally, the labor of discharg- 
 ing, done by contract, must be well paid for. This work, 
 however, is not really injurious to the health of the la- 
 borer, as men who were at it for years never showed any 
 symptoms of sickness. 
 
 Not only for the Mitscherlich system, but for all other 
 processes a method has lately been recommended to re- 
 move the sulphurous acid as much as possible before the 
 stuff leaves the digester. This is the method of Carpen- 
 ter and Schulze in Berlin, heating the leaches after fin- 
 
THE MANUFACTURE OF CELLULOSE. 102 
 
 foiling the operation of digestation, by driving comprised 
 and heated air by a blower through a perforated pipe 
 into the boiled mass, whereby the stuff becomes fibered 
 and at the same time are formed resulting combinations 
 which otherwise do not form before draining, after leaving 
 the digester, under the influence of atmospheric air. In 
 the upper part of the boiler is another perforated pipe, 
 through which air and sulphurous acid can be drawn off. 
 
 When the cellulose is removed from the digester, and 
 the boiler is swept, if necessary, the heating pipes are then 
 knocked with wooden hammers to remove the sulphate, 
 often depositing on the pipes in considerable thickness, 
 because as a poor conductor of heat it very much injures 
 the heating capacity. 
 
 Every single pipe system must be separately tested to 
 see whether it is tight, does not let through steam, and 
 also, whether by leach having entered and formed sulphate 
 (gypsum) inside, it has not become stopped up. In the 
 ■first case the leak must be corked or a new piece of lead- 
 pipe must be set in, which can be rapidly accomplished, if 
 the pipe pieces are not soldered but screwed together 
 with bronze flanges. When the pipes are stopped up>, mur- 
 iatic acid is filled in and slowly driven through with a 
 little pressure of steam, finally after every operation the 
 whole lining must be well looked over, especially the top. 
 The heat prevailing inside soon dries up the face of the 
 wall completely except at the spots where the acid has 
 penetrated the joints where it trickles out again as moist- 
 ure and thus shows plainly, where it is most necessary 
 to do the joints over. If this important matter is neg- 
 lected the complete destruction of the digester will soon 
 be caused. The saving of time at this point can therefore 
 not be recommended. 
 
 In regard to using hard lead for heating pipes, it must 
 be finally remarked that it is followed by a number of in- 
 conveniences which long ago made desirable a substitute, 
 and finally led to the use of copper, the resistance of which 
 against sulphurous acid was not regarded with much favor. 
 On account of its greater power of resistance the hard 
 lead pipes were first chosen, which in consequence of the 
 steam going through under pressure in long coils, have 
 to stand greater differences of temperature. But for that 
 lead is very little suited. Being an imperfectly elastic 
 
104 THE MANUFACTURE OF CELLULOSE. 
 
 body, it does not contract to its original form, when on ac- 
 count of previous raising of temperature it had suffered 
 expansion. Moreover there are occasionally stronger and 
 weaker layers, bends., which in pipes becomes suspicious 
 as constrictions and dilations, also cracks, through which 
 leach and stuff are entering and causing partial or total 
 stopping up. All these influence the heating effect and 
 prolong the duration of an operation. This is still exag- 
 gerated by the layer of separated lime salts, deposited 
 around the heating pipes,, being a poor conductor of heat, 
 and which cannot be as quickly and thoroughly removed 
 from the soft metal which is easily injured. Lead is in 
 itself little suited for heating pipes, because it is not a 
 goo'd conductor of heat, and the pipes, in order to be 
 durable, must be of considerable thickness. Not one or all 
 these disadvantages however is met with in copper. Cop- 
 per pipes, by virtue of the great firmness of this metal, 
 can be made quite thin, at a thickness of wall of from 
 3 to 4 mm., and besides copper is an excellent conductor 
 of heat. Changes of temperature do not cause' the: bad 
 effects,, as with lead, and the coil does not form one single 
 stiffness, but is composed of a number of sections., 4 to 5 
 meters long, connected by couplings of acid proof bronze, 
 which at any place may be exchanged at pleasure. The 
 resisting capacity of copper against sulphite leach has 
 proved to be greater, as in the first operation it. gets cov- 
 ered with a black coating of the oxydes of copi- 
 per, which very likely is produced, by the action of the 
 glycose, present in the leach and which prevents further 
 action. On account, of the greater heating capacity of cop- 
 per pipes less of them are necessary for one boiler, than 
 lead pipes; for the cubic-meter volume about 2.5 meter of 
 pipe. They are varyingly arranged, according to whether 
 they are intended 1 for horizontal or upright digesters. In 
 the latter Lhey are run along side the wall, in the former 
 at the lower side in coils measuring about 1-5 of the wall 
 and the water of condensation is removed by suitably 
 arranged traps,. 
 
 To complete this, treatise on heating pipes, not pub- 
 lished until after the end of 1894 in the Papier Zeitung, 
 the author is in the position to state that in 1886 he was 
 negotiating about the furnishing of copper pipes for a 
 Mitscherlich digester, with a cellulose factory in Steyer- 
 
THE MANUFACTURE OF CELLULOSE. 105 
 
 mark, which already in 1885 or earlier has furnished such 
 pipe systems to other factories, which were very well sat- 
 isfied with its work. 
 
 An operation as described above, yields about 10,000 
 kilos of finished dry cellulose and according to several ex- 
 periments by the author for 100 kilos cellulose about 
 0,956 volumeters or 0.62 cubic meters of wood (pine) 
 are needed on the average, which is exactly accordant 
 with Mitscherlich's statements, who calculates 0.63 cubic 
 meters of wood for 100 kilos of cellulose. At this the relation 
 between testmeter and volumeter is not, as generally stat- 
 ed in books., accepted 7:10, but 65:100, which latter fig- 
 ures have become fixed by practice after many trials. 
 
 Every cellulose factory, according to^ its working meth- 
 od and the kind of wood mainly used, will certainly, in 
 regard to the average yield in cellulose, obtain a percen- 
 tage number, somewhat differing, from the results of 
 other factories. So for instance, according to an older 
 publication at the Weissenborn factory they figure 2,400 
 kilos cellulose for 12 testmeter, consequently 200 kilos for 
 1 testmeter and 140 kilos for 1 volumeter. This result 
 can, on account of being so high, be accepted as correct 
 only for very good and barked material. The specific 
 gravity of the air dry pine wood is 0.47, consequently 1 
 testmeter weighs 470 kilos. One cubic meter, i. e., one 
 volumeter of trimmed pine wood weighs 320 kilos, con- 
 sequently 1 volumeter would be 0.68 or about 0.7 test- 
 meter, which however, ia somewhat too high, according 
 to the authors experience. The difference is by no 
 means unimportant, because as a rule, the incoming wo d 
 is piled up and accepted per volumeters, but figured and 
 paid per festmeter. In the run of the year a considera- 
 ble number of meters may thus be paid over. 
 
 From the balance sheets of a southern German factory 
 it is learned that per cubic meter pine would equal 156 
 kilo air dry cellulose. 
 
 A northern German factory worked up in one year 
 52.10 volumeters of wood and produced in the same 
 period 715,000 kilos of stuff at large (I. II, III,) conse- 
 quently 1 volumeter would yield 137 kilos air dry cellu- 
 lose, which keeps the middle between the above men- 
 tioned figures. 
 
 The cellulose factory Waldhof, before its new plant 
 
106 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 was started, had a daily production of 1,400 centner dry. 
 The consume of wood amounted to 170,000 testmeters per 
 year. The yield of cellulose, amounting to 25,000,000 kilos 
 per year it follows, that for 1 testmeter 148 kilos must be 
 figured, or for 1 volumeter 104 kilos of cellulose. Sup- 
 posing now, that these 104 kilos of cellulose were ob- 
 tained from 1 volumeter embarked, equal to 0.8 volumeter 
 of barked wood, the- yield from a full volumeter of 
 barked, good wood amounts to 130 kilos of cellulose, 
 
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 which does not differ much from the Weissenborn result. 
 About the proper occurrence inside of the digester, dur- 
 ing the process of digestion up to the present com- 
 paratively few observations have been made. A. Herr Nils 
 Pedersen has in No. 19 and 34 set 1890 of the Papier 
 Zeitung published quite interesting researches, which in 
 this volume, serving more practical purposes, could not 
 be together admitted. Only the final results of the inves- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 107 
 
 tigations about leaches, which were taken in certain in- 
 stances during the operation, shall here be regarded as the 
 figures obtained were used in a graphical description, which 
 gives a plain picture of the decomposition of the wood 
 in the digester. In both figures, at the base are marked 
 horizontally the hours required by the process, after the 
 temperature in the digester had reached 105°; the ordi- 
 nates, i. e., the vertical lines give the per centage; the 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
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 temperatures of the digester at the different times are 
 marked at the upper horizontal line. 
 
 Curve I shows how the sulphurous acid gradually is 
 forming combinations with the organic constituents. 
 Curve II shows how the organic constituents are accumu- 
 lating in the course of time, expressed in per cent. 
 
 Curve III shows how the loose combinations first are 
 continuously forming, up to a point from where the curve 
 descends, consequently decomposition is commencing. 
 
108 THE MANUFACTURE OF CELLULOSE. 
 
 In serving an explanation to this, the investigations 
 have proved that in the leach part of the sulphurous 
 acid is existing in a loose combination, which is decom- 
 posed by boiling. By adding a stronger acid, for in- 
 stance, sulphuric acid, the decomposition ensues still 
 easier. The same observation was made by the author 
 years ago, when, for the purpose of rendering the leach 
 inoffensive it was evaporated in large open vessels and 
 for the more rapid driving off of the sulphurous acid, sul- 
 phuric acid was added with success. 
 
 The curve indicating the organic constituents is as- 
 cending in almost a straight line, in the beginning so also 
 is the sulphurous acid. But it is remarkable that where 
 the loose combinations are beginning to get decomposed 
 the curve of the sulphurous acid does not ascend as rapid- 
 ly as before, because here not only the free sulphurous 
 acid is acting on the organic constituents, but also the 
 sulphurous acid, split off the loose combinations, but al- 
 ready counted in once, as combined with organic con- 
 stituents. 
 
 In the second figure the results of the analysis of a sec- 
 ond leach, richer in lime, are entered, just as before and 
 for better comparison, the curves of the first figure are 
 here repeated in dotted lines. Curve I reprsents both loose 
 combinations together. As appearing from the illustra- 
 tion, also the two' other curves deviate very little. 
 
 These researches by Mr. Nils Pendersen, according to 
 Dr. Frank's statement, were invited by and built upon 
 preliminary investigations^ which he had made sometime 
 ago and which he has published already in the year 1888. 
 
 Corresponding to the order in the chapter about leach 
 making, the digesting process of Eitter-Kellner shall now 
 be briefly mentioned here. In this case two upright boil- 
 ers are used, lined with small plates of lead, held to- 
 gether by rings and bands of lead, which have two per- 
 forated bottoms, between which the wood is filled in. The 
 digesters are connected by pipes in the manner shown in 
 Fig. 51, taken from the letter of patent. A and B are 
 two iron vessels with inside lead lining, vessel C con- 
 tains the solution of sulphurous acid, Cl fresh water. A 
 pipe 1 leads from C to Cl by branches 2 and 3 with regu- 
 lating valves 5 and 6 into both digesters and enters a lit- 
 tle above the grates a and b, which keep the wood immerg- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 109 
 
 ed into the liquid. The pipe 4 is to the right communicating 
 with a steam boiler and a vessel with sulphurous acid. Pipe 
 4, which to the left at c ends into the gutter cl, has two 
 branches 7 and 8, which enter the bottom of the boil- 
 ers, where they are closed with regulating valves 9 and 10. 
 Besides pipe 4 has two branches 11 and 12, with the regu- 
 
 Fig. 51. 
 
 lating valves 13 and 14, and above and into boilers. To 
 discharge the digesters, i. e., to let off the leach the out- 
 lets 17 and 18 are provided. The work is carried on in 
 the following manner: Suppose boiler A to contain 
 wood, which is exposed to the action of twice used acid 
 solution, while digester B is filled with fresh wood. Then 
 the valves 6, 9 and 10 are opened, while 5, 13, 14, 15 and 
 16 remain closed; the fresh leach therefore runs through 
 
110 THE MANUFACTURE OF CELLULOSE. 
 
 pipe 7, 4 and 8 into digester B. When A is filled with fresh 
 pipe 7, 4 and 8 into vessel B. When A is filled with fresh 
 leach, valve 6 is closed and valve 14 opened, whereupon 
 steam .enters through the pipes 7 and 8 into both diges- 
 ters and the wood boils. 
 
 When the boiling is finished, valve 16 is closed again 
 and valves 14 and 15 are opened.; the sulphurous acid and 
 the steam are blown through pipes 12 and 4 into the gutter 
 c, or for recovery they are regenerated in suitable ap- 
 paratuses. Afterward all liquid is removed through out- 
 let 18 from the digester B, in which nothing is now con- 
 tained but decomposed wood. The solution from digester 
 A by admitting fresh water from vessel Cl is then driven 
 into digester B in the former way. and is now solution 
 once used. The operation is then repeated, thereafter 
 the pipes 2, 11 and 7 shut off and the digester A emptied 
 and again filled with fresh wood. 
 
 From there the operation repeats, only the two di- 
 gesters exchange rolls. In place of two digesters, several 
 may be employed at the same time, whereby it would be 
 possible to use the solution four to eight times and to 
 use it up completely. The single operations, become then 
 considerably shortened and a product is 'obtained, excel- 
 lent in every direction. 
 
 When especially white cellulose shall be made, the wood 
 is soaked with leach in the digester and before heating, 
 by means of a pump sulphurous acid is forced in until a 
 pressure of at least two atmospheres is reached. Not be- 
 fore then either steam, or steam mixed with sulphurous 
 acid at a temperature above the boiling point is let in, 
 until the pressure has reached about fiom 3 to 5 atmos- 
 pheres. By this in the first state the decomposition of the 
 wood, in the second the bleaching of the fibre is effected. 
 The stuff becomes white, does not contain any hard con- 
 stituents and can be further worked without first passr- 
 ing a knot catcher. The boiling process requires about 
 14 to 18 hours, with low pressure; however, it may be pro- 
 longed to 36 hours. 
 
 Dr. Kellner amply describes his own process of boiling 
 in set, 1894 page 2586, as follows: 
 
 Although owning the first patents for rotating digester, 
 for the reason that my first manufacturing was done with 
 such, I have, however, soon gone over to the by far more 
 
THE MANUFACTURE OF CELLULOSE. Ill 
 
 practical form of the upright fixed cylinder. My digest- 
 ing apparatus since consists of an upright fixed cylinder, 
 which on top and below carries a large manhole, fastened 
 with lock-screws. 
 
 This boiler, in the beginning of my method, was lined 
 with sheets of lead, which were clinched to the boiler, or 
 soldered to strips of hard lead, which, in swallow-tailed 
 rabbets between the sheets of the boiler, where they met, 
 were connected with the iron thermo-chemically. D. E. 
 P. 34074-1884. 
 
 In Fig. 52, for example, C is the strip of hard lead, A 
 the boiler-wall, B the lead lining, J the clinche to connect 
 the boiler sheets A to A'. Or the lead sheets are with 
 easy fusible metal directly soldered to the digester walls. 
 D. E. P. 3725. As not in every locality experienced lead 
 burners can be had, I have tried from the beginning to do 
 away with the lead in the digester. 
 
 *r aarj-k 
 
 bo 
 
 Fig. 5t 
 
 My first patent regarding this was applied for in 1887 
 by the Messrs. Jung and Lindig to insure profound secrecy, 
 and presented in an altered condition two years later, hav- 
 ing been refused the first time. My main object was to ef- 
 fect the double decomposition between the sodium silicate 
 and the icalcium bisulphite, at the end of which reaction 
 sodium sulphite and calcium silicate are formed. The lat- 
 ter serves to close the pores of the sulphurous acid resisting 
 substances which are made into a mass with liquid glass. 
 Digesters coated in this manner have proved to be very 
 satisfactory, although very many factories have departed 
 from this process, and returned to the old manner of lead 
 coating. 
 
 In order to prevent the lead from being attached, should 
 a leak in any part of the mass occur, I have recommended, 
 as illustrated in Fig. 53, to cover the digester A with a 
 jacket B of thin tin and to fill the interlying space with 
 the heavy residue obtained from the petroleum refineries. 
 
 Into the outer jacket m enter the pipes m2 and m3 for 
 
112 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 m and, outlet of the liquid residues and ml for emptying. 
 In this manner the boiler also receives heat from outside, 
 and forms at any place, laid bare by cracking of the inner 
 lining, a protecting coat of mono-sulphite of lime. This 
 jacket, against the one proposed by Soloman, has the ad- 
 
 TO« 
 
 Fig. 53. 
 
 vantage, that inside of a few hours it can be completely re- 
 moved in case of repairs becoming necessary, and that 
 danger of explosion is altogether excluded. In the case 
 of any rivet leaking, the sulphurous acid leaking out, es- 
 capes through the hot oil in the form of gas, which is at 
 once noticed. 
 
THE MANUFACTURE OF CE-ULULOSE. 112 
 
 With digesters, the jacket of which is heated with steam, 
 a dangerous moment is prevalent, as the space between 
 boiler and jacket is entirely without protection against sul- 
 phurous acid and therefore injuries to the inner digester 
 cannot be noticed any sooner, than when also the jacket 
 has become defective — which may cause deplorable catas- 
 trophes, as will be told later on. 
 
 The heat required in boiling, I introduced by direct 
 steam, as I have departed from indirect heating for the 
 reason that the heating coils get rapidly covered with 
 mono-sulphite of lime, consequently do not well con- 
 duct the heat and carry no end of dirt into the stuff. It 
 is indeed not necessary to work with indirect steam, when 
 at liberty, to prepare the leach in such concentration, that 
 it still has the concentration required for boiling, after 
 adding the water of condensation from the steam. Such 
 was easy, because in my leach making apparatus I can 
 produce leaches of to 7.5°B without difficulty, while Prof. 
 Mitscherlich could produce but weak leaches in his towers. 
 
 In regard to the boiling itself, according to my method 
 it is not necessary to steam the wood previous to the treat- 
 ing with sulphurous acid, thereby diluting the latter. 
 After charging the boiler the leach is at once let in by a 
 pump through a pipe put through the open manhole, in 
 such quantity and concentration that its volume is so much 
 increased by the water formed by the condensed steam 
 that when a temperature of 105 °C is reached the whole 
 of the wood is covered with liquid. The concentration is 
 at the start made high enough so that after dilution with 
 the water of condensation just that concentration results 
 with which the boiling is desired to be carried through. 
 
 In this manner at the beginning of the period decom- 
 position exactly the same conditions and proportions exist, 
 which are arrived at with indirect heating, but with 
 the difference that much time is saved, because by the use 
 of large steam pipes a large boiler, producing about 6,000 
 kgr. stuff, is in 1-| hours brought to 105 °C, a result which 
 with indirect heating requires several hours. 
 
 I then heat further to about 109 °C, then shut off the 
 steam and leave the wood about 3 hours under the influ- 
 ence of the hot leach, so that it can penerate every particle 
 of wood, before the temperature is further raised. In 
 this manner I avoid all formation of splinters. This pause, 
 
114 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 which in my method is called "stand-still," can be modified 
 according to the nature of the wood and its degree of dry- 
 ness. Absolutely dry wood does not require any stand- 
 still, or less prolonged stand-still than damp wood, be- 
 cause the leach can penetrate quicker on account of the 
 capilarity. I then raise the temperature quickly up to the 
 desired point, 120-138 °C, again shut of the steam and re- 
 peat this supplying of steam at regular intervals. 
 
 To facilitate the entering of steam and to eliminate the 
 hydrostatic pressure in the digester, I let off from, time to 
 time through the so-called off-gas-valve provided at the 
 upper neck of the boiler, some leach (sulphurous acid 
 mixed with steam) into the condensating-apparatus, pecu- 
 liar to my process. 
 
 In fig. 54 such condensing arrangement is sketched. Sul- 
 
 ir^~ 
 
 Fig. 54. 
 
 phurous acid and steam enter at a into the lead pipe coil b, 
 condense there, and flow out at c as liquid sulphurous 
 acid. The cool water runs through pipe d into the mid- 
 dle space f, rises at the bottom between the walls and 
 around the coil and leaves through the over run pipe g. 
 
 During the boiling samples are taken from time to time 
 and these have the following characteristic signs: In the 
 beginning the leach is wine-yellowish and somewhat tur- 
 bulent, then it gradually becomes darker and clearer. After 
 a few hours I commence to test the free sulphurous acid 
 volumetric with a normal iodine-solution. 
 
 It is my special discovery that the sulphurous acid dur- 
 ing the boiling does not, as Tilgham and others have sup- 
 posed, becomes oxydized into sulphuric acid, but enters 
 
THE MANUFACTURE OF CELLULOSE. 115 
 
 in organic combinations, and forms organic sulfinic com- 
 binations. And my discovery it is also that the sulphurous 
 acid, keeping in this organic combinations does not show 
 the iodine reaction — therefore the still uncombined sul- 
 phurous acid can be estimated by titration with iodine dur- 
 ing boiling. 
 
 When making sulphite-cellulose I have endeavored to 
 produce a stuff giving general satisfaction in every way, 
 consequently felting tough and firm enough to bind wood 
 pulp or earth for ordinary paper and which at the same 
 time shall be also opaque, soft and very easy bleachable, and 
 which could be worked into finer and finest papers. 
 
 By my process it is possible to produce just as tough, 
 but there certainly is just as difficultly bleachable cellu- 
 lose, as by those processes, which work with low pressure 
 and use indirect steam. 
 
 The reason why the fibre produced at low pressure and 
 with direct steam is firmer is that the inter-cellulose sub- 
 stance, i. e., that body which fills out the capilary of the 
 fibre, the cave of the cell, has not diffused through the 
 walls of the cells, because the boiling was done under con- 
 ditions which do not permit diffusion. Because when the 
 concentration of the leach in an organic substance out- 
 side of the cells is equally high with that part which has 
 entered the cells there is no occasion for the latter to force 
 its way through the membranes; if however, when boiling 
 with direct steam, the leach outside of the cell, because 
 of the water of condensation, becomes diluted, then the 
 concentrated solution contained in the cells diffuses 
 through the walls of the cells. 
 
 The work is performed as follows : 
 
 TABLE FOE BOILING. 
 Charging the boiler with wood 10 min. 
 
 do with tramping down 30 min. 
 
 Filling in leach 20-30 min. 
 
 Making fast the upper manhole 15 min. 
 
 Steaming up to 109 °C 1 hour, 30 min. 
 
 Stand-still 3 hours 
 
 Steaming to the desired temperature -| hour 
 
 Duration of boiling with letting gas off leach and 
 
 several times supplying steam 8-14 hours 
 
 Gasing off into concentration 1 hour 
 
 Blowing out 15 min. 
 
116 THE MANUFACTURE OF CELLULOSE. 
 
 Admitting water and discharging 30 min. 
 
 Cleaning the digester 1 hour 
 
 Total about 21 hours. 
 
 Therefore, including small repairs of the digestors, 
 one operation can be performed every 22 to 30 hours. 
 
 Such repairs are reduced to a minimum, because besides 
 the manholes, the boiler has but one opening for admit- 
 ting steam, one for letting off leach, one for gasing off, and 
 one to arrange a thermometer and stop cock for taking 
 samples. 
 
 The nest described apparatus is designed to avoid losses 
 of sulphurous acid in boiling, as well as defiling the stuff 
 with precipitates of mono-sulphites. 
 
 In the sulphite processes as a rule the cold leach is filled 
 in together with the wood, and by inner or outer heating 
 gradually raised to the required temperature, at which 
 the decomposition of the wood in its fibres takes place. 
 By this heating up a considerable amount of mono-sulphite 
 of calcium is generally separating from the leach, very likely 
 in consequence of a part of sulphurous acid being set free 
 by the heating, and acts disadvantageously in that it forms 
 crusts upon the heating coil or upon the inner face of the 
 digester walls, as also because it discolors the stuff, which 
 afterwards requires stronger bleaching. To meet this dis- 
 advantage according to the present invention (America pat- 
 ent No. 542,932 and Austrian patent No. 33,685 and 56,- 
 889) the leach is first heated outside of the digester in a 
 special heater, whereby the separation of the mono-sulphite 
 takes place outside of the digester and is then let over 
 by the digester filled with wood. Thereby the sulphurous 
 acid, being set in the heating of the leach, is condensed in 
 a coil-cooler and used again as solvent for the separated 
 mono-sulphite. 
 
 Fig. 55 shows, a vertical cut of an upright heater with 
 condenser. It mainly consists of a vessel a with steam- 
 heating-ooil h, into which the steam enters at c, while 
 at the end of trap e is connected. Both above and below 
 is also a. thermometer t. Below at the vessel there is an 
 outlet and cleaning valve n. The leach to be heated enters 
 ( at f into, the vessel and leaves at g. On top the vessel 
 is connected by pipe h with the one end j of a coil con- 
 denser, while the other end jl leads to the reservoir for the 
 product of condensation. The condensor k consists of 
 
THE MANUFACTURE OF CELLULOSE. 
 
 117 
 
 two concentric vessels, of which the inner has openings 
 below. The condensing medium flows through pipe 1 in 
 the inner vessel, rises in the space between the inner and 
 outer vessel and runs off through pipe 11. 
 
 To facilitate the separation of the mono-sulphite and 
 at the same time to keep it floating during heating, a 
 stirring arrangement is provided in the vessel (not repre- 
 sented in the sketch). 
 
 The method proceeds as follows: The heater is filled 
 with leach and is heated above the boiling point, with the 
 stirring arrangement steadily going on. When this point 
 
 Fig. 55. 
 is reached the stirring is stopped, the separated mono- 
 sulphite permitted to settle, and the hot leach transported 
 to the digesters, already charged with wood. The cooled 
 gases, principally consisting of sulphurous acid are liqui- 
 fied in the condensor and let into the storage tank, into 
 which are also let the gases from the digester, after finish- 
 ing boiling. After discharging and previous to re-charg- 
 ing the heater, the liquified sulphurous acid is let from 
 the reservoir into the heater, to dissolve the separated 
 mono-sulphite deposited at the bottom, when cold leach 
 is again filled in and heating started anew. 
 
 Every process employed in the manufacture of cellu- 
 lose and named after its inventor, prescribes for the proper 
 boiling of tne wood a certain way, which, although in the 
 principle the same, every different factory shows more or 
 
118 THE MANUFACTURE OF CELLULOSE. 
 
 less variation, suitable to local conditions, the experience 
 of the manufacturer or manager and master of boiling, 
 the nature of the wood worked, and other like conditions. 
 In the following we describe some such varying in par- 
 ticulars more or less from each other, but all practically 
 tried methods, of boiling: 
 
 1. The digester is heated, the slower the better, up to 
 116°C, and about 2.8 atmospheres, and then the steam is 
 shu + off and a stand-still follows, which when desired can 
 be extended to 8 hours. The pressure, at the beginning 
 of the stand-still rises somewhat and then gradually falls 
 and when necessary, by letting off steam, is brought down 
 to at least 2 atmospheres. Then follows renewed steam 
 supply up to the temperature of 136°, 4 to 5 atmospheres 
 pressure, and at this the digester is kept, until according 
 to looks, smell and strength of the leach in sulphurous acid 
 the boiling may be regarded finished, when the steam is 
 blown off as quickly as possible. The duration of the 
 whole operation according to this method amounts to 18- 
 22 hou^s and is principally suited for cellulose designed 
 to be bleached. 
 
 2. The digester is within about 3 hours brought to 
 105° and then left at stand-still for 3 hours more. After 
 that it is blown off down to 3 atmospheres and the heating 
 with steam continued until up to 125 °C. Blowing off 
 steam is repeated, until the temperature goes back to 120- 
 125° and then the process is finished under continuous 
 supplying of steam in about 10 to 12 hours at 130° C. Dura- 
 tion of the operation, 14 to 18 hours. 
 
 3. Heating up to 105 °C and 2^ to 3 atmospheres with- 
 in 3 to 4 hours, Then stand-still, which according to re- 
 quirement and use lasts 1 to 3 hours; then continuing heat- 
 ing, so that at 108°C about 2^ to 3 atmospheres, at 115° 
 about 3 atmospheres, at 123° about 4 atmospheres, at 130° 
 about 4^ atmospheres, at 135° about 5 atmospheres of 
 pressure are obtained; the highest temperature permitted 
 is 135 to 140°; if rising the steam-supply must be shut 
 off. Finishing of the operation at 0.56 to 0.5$ of sulphur- 
 ous acid, which should be accomplished in about 8 to 9 
 hours after the stand-still. Duration of operation, 10 to 
 ]4 hours. 
 
 Against those mentioned above, the Ritter-Kellner meth- 
 od possesses the following peculiarities and advantages: 
 
THE MANUFACTURE OF CELLULOSE. 119 
 
 1. The possibility of employing in the dressing of the 
 wood, a diminution in the sulphite process as well as in 
 the soda process advantages; first of a uniform diminution 
 and with the consequent uniform product, and second, of 
 the rapid penetration ' of the particals of wood with the 
 leach, and consequently stuff free of splinters; another ad- 
 vantage is the shorter duration of boiling. 
 
 2. Employment of a leach, consisting of a double salt of 
 the sulphurous acid: Calcium-magnesia-bisulphite and 
 produced by using "Dolomit" in preparing the leach. The 
 advantages are, first, a less precipitation of lime in the di- 
 gester, because the monosulphite of the magnesia is solu- 
 ble in water (the combination of lime, however, is decom- 
 posed by the magnesia during boiling) and, second, whiter, 
 tougher stuff, because the sulphurous acid is longer re- 
 tained. 
 
 3. Employment of a leach containing more then 2 
 molecules of sulphurous acid to 1 of molecule of the base 
 base (the composition of which is conse- 
 quently nearer to a hypothetic "Trisulphite"). 
 The advantages are, first, the precipitation of 
 lime in the digester is completely eliminated, 
 because according to the Mariott law during boiling, the 
 molecule S02 required in the dissolving of Ca S03, on ac- 
 count of the pressure produced by the S02 in excess, can- 
 not escape into the vapor space of the digester; second, 
 the possibility to produce at liberty absolutely white and 
 cottonlike cell stuff, little transparent and easily bleach- 
 able, consequently most valuable for the manufacture of 
 fine and finest papers. 
 
 4. The method to submit the sulphurous acid contain- 
 ing gases, coming from the furnaces, before entering the 
 absorption apparatus to an energetic cooling. The advan- 
 tages are the possibility to produce highly concentrated 
 solutions in relatively small apparatuses, because as well 
 known, the capacity for absorption (efficient of dissolving) 
 of a liquid for gases increases with decreasing temperature. 
 
 5. The method to force these cold gases by artificial 
 pressure (draft) through any number of absorption ap- 
 paratuses. The advantages are, first, complete absorption 
 of the sulphurous acid, consequently greatest effect; sec- 
 jnd, independence of air currents and outside tempera^ 
 iura; third, constantly uniform production in qualitative 
 
120 THE MANUFACTURE OF CEIZjULOSE. 
 
 and quantitative respect; fourth, no injuring of neighbor- 
 ing vegetation; fifth, production of possible highly con- 
 centrated leach. 
 
 6. The employment of upright cylindrical digesters 
 with combined direct and indirect, or only direct heating. 
 The advantages are, first, rapid boiling, because there is no 
 loss of time by a warming up of long duration; second, ex- 
 cellent circulation; third, no hard lime deposits at the heat- 
 ing pipes; fourth, convenient tending of the digester "'and 
 rapid charging and discharging. 
 
 7. Employment of rotating digesters with direct heat- 
 ing. The advantages are, first, for smaller plants simpler 
 attending; second, cottonlike stuff. 
 
 8. Different manners of lead lining, and the employ- 
 ment of water-glass for the production of acid-proof pro- 
 tecting mass. The advantages are, first, rapid execution 
 of repairs; second, jointless lining. 
 
 9. The lining of this protecting mass with plates of 
 hard glass. The advantages are, first, greater cleanliness; 
 second, instant visibility of perhaps occasional cracks of 
 the lining through the glass (as brown lime-spots); third, 
 greatest durability; fourth, best closing at the joints. 
 
 10. The method to control the proceeding of boiling 
 in its progress by titration with iodine solution. The ad- 
 vantages are, first, the possibility to exactly determine the 
 ever standing of the transformation; second, to be able to 
 produce several qualities, tough and soft, as desired. 
 
 11. Method to recover the sulphurous acid retained in 
 the digester after finishing boiling, by conducting it mixed 
 with steam, through condensing coils. The advantages are, 
 first, recovery of about 18 to 20 per cent of all the sul- 
 phurous acid employed; second, no molestation of the 
 neighbors; third, supply of aqueous sulphurous acid for 
 the production of possibly strong leaches; fourth, remov- 
 ing of occuring sulphate crusts in the obsorption appar- 
 atuses. 
 
 12. Method to employ the sulphite digester under pres- 
 sure (blow-off method). The advantages are, first, very 
 rapid discharging, because it is not necessary to wait un- 
 til the pressure has gone down; second, open stuff can be 
 easily washed out and with little water. 
 
 The other sulphite methods, already mentioned in the 
 chapter of leach-making, according to Hager, differ in 
 
THE MANUFACTURE OF CELLULOSE. 121 
 
 their principal characteristics of the digesting process as 
 follows : 
 
 Ekman boils in, a cylinder vessel, surrounded by a steam 
 jacket, lined with lead and turning on side pins for charg- 
 ing and discharging. The digester about 1.3 meters wide 
 and 4 inches high after being charged with wood is filled 
 with the leach until the wood weighted with perforated 
 sheets of lead is covered by it. By steam from a separate 
 boiler a special over-pressure is then produced in the jacket 
 according to the following rule : Within the first two hours 
 the pressure in the inner vessel should be raised 0.7 atmo- 
 spheres, in the next two hours about 1.4 atmospheres per 
 hour, in the next hour by one, and in the two following by 
 0.7 atmospheres each. With this final pressure of 6 at- 
 mospheres the digester is left, until a peculiar smell of the 
 vapor let out by a valve, or a sample taken, indicates the 
 end of the process. The, steam is then blown off, the liquid 
 drained off through a leaden strainer arranged at one end, 
 and finally after turning the digester the contents are 
 dumped, to be washed or ground in the ordinary manner. 
 The product by this method is claimed to yield 32.68 per 
 cent of wood charged green or 40 per cent of air dry boiling 
 wood. 
 
 Francke in Molndal employs a horizontal cylinder vessel 
 of steel-plate of 2.2 meters diameter and 12.5 meters 
 length, with a 6 millimeter strong lead lining, forming a 
 vessel by itself, soldered together from sheets of lead, 
 which is fastened .to the outer vessel by rings of brass in 
 distances of 1 meter. The digester, which is slowly rotat- 
 ing (once in 10 minutes) and carries side catches to lift 
 the wood, rests with wide flanges on rollers, and receives 
 its rotation by a worm-movement. The digesters are first 
 filled to about three-fourths height with pieces of wood, 
 and then with solution of from 4 to 50° B so ,that the 
 wood is well covered. The boiling is effected at a pressure 
 of about 3.5 atmospheres, produced by steam, entering 
 through a hollow pin provided at one end and regulated by 
 a reduction-valve. 
 
 When the boiling has lasted about 11 hours, some of the 
 mass is blown out through a leaden cock for sample and 
 this sampling is repeated from time to time, until showing 
 the right quality, for which according to quality and moist- 
 ure of the wood from 12 to 17 hours are required. After 
 
122 THE MANUFACTURE OF CELLULOSE. 
 
 finishing boiling the gases and vapors contained in the 
 vessel under pressure are blown over to the sulphite tower, 
 to be used again for making new leach. Then the leach 
 is also removed by letting it run off, the boiled wood is 
 washed twice and finally dumped into drain-boxes. For 
 the described operation for 1,000 kilo wood, 900 to 1,250 
 liters of leach are necessary. 
 
 In addition to the above the more detailed description 
 of the boiler, as taken from the American patent, No. 
 304,092, is given. 
 
 The boiler, which is not as stated above, 12 meters, but 
 only about 6 meters long by 2 meters in diameter, is made 
 of tinned iron and provided with a lead lining. The steam 
 is introduced by pipes to the right and left, which in the 
 digester itself are perforated, so that the steam can freely 
 steam into the mass. The boiler turns about its long axis, 
 not in pin-boxes, however, but upon rollers. To this pur- 
 pose three heavy rings are arranged at the circumference 
 of the digester, each of which rests on two rollers. The 
 turning of the digester is accomplished by a worm, catch- 
 ing into a worm-wheel arranged at the circumference. 
 The fastening of the lead inside is done by laying it loose 
 against the steel plates of the digester, where it is held 
 by straddle-rings. The lead sheets should be as: large as 
 possible, and each should form a complete ring. The joints 
 are soldered together and the finished covering is then fast- 
 ened to the boiler wall by means of the rings mentioned. 
 These rings are split open and can be driven apart by 
 wedges, whereby the bad is pressed close to the walls. 
 There is an interlayer between lead and vessel. To be able 
 to notice leaks in the lead, the jacket of the digester is 
 provided with a great number of holes, which can be closed 
 by cocks. The cocks are open during working. If it now 
 happens that the lead lining is no more tight, the leach 
 will run away at one or more places through the cocks; 
 these cocks are closed meanwhile until the place to be re- 
 paired, which is easily to be found by the position of the 
 cocks can be taken in hand. 
 
 These digesters have been proven in practice, as have 
 also the lead lining, fastened by means of the straddle- 
 rings to be practical. To spare the lining, the digester 
 need not rotate continuously, but may be put in motion 
 from time to time, or eventually also towards the end for 
 
THE MANUFACTURE OF CELLULOSE. 123 
 
 quicker discharging. The boilers offer the advantage that 
 they prevent the depositing of sulphate of lime and then 
 prevent deterioration of part of the stuff. 
 
 The general characteristics of the boiling process accord- 
 ing to Pictet and Brilaz have already been stated. There 
 remains to be mentioned only that after boiling there are 
 contained in the leach not only a quantity of different sub- 
 stances, like gum, resin and etherical oils, but also almost 
 all the sulphurous acid, which could be recovered, where- 
 fore in this method it is especially aimed to use the leach 
 over again, by charging it after the boiling operation into 
 a second and also third digester, previously filled with 
 wood, until it has become saturated with other substances. 
 But as the liquid is retained in the wood by the power of 
 capilarity, and cannot directly flow from one digester into 
 another, the process for this reason requires that the wood 
 after discharging be pressed out, to recover the liquid. By 
 evaporation the sulphurous acid is separated from the 
 resins, etc., in solution, to be recovered by absorption. 
 
 Regarding this apparently very simple method it must 
 be remarked that the sulphurous acid made liquid at 10 
 to 15° below zero, evolves a very great pressure, where- 
 from ensues the fact that at a temperature of 85 °C in the 
 boiler there is already prevailing a pressure of 7 atmos- 
 pheres, notwithstanding the considerable dilution of the 
 sulphurous acid, because at this temperature only very 
 small quantities of the sulphurous acid are dissolved in 
 the water. As it is very difficult to exactly regulate the 
 low temperatures this simple method offers considerable 
 danger on account of the high pressures produced as soon 
 as the temperature is slightly raised. 
 
 Besides must be remarked that in this process part of 
 the sulphurous acid becomes oxidized at higher temper- 
 ature, thus blackening the wood substances, the more as 
 in the leaches the protecting lime is missing,, which in other 
 method, existing as monosulphite of lime, gives off the 
 sulphurous acid and absorbs and neutralizes the sul- 
 phuric acid formed. 
 
 Flodquist employs a revolving spherical boiler of steel 
 plates, lined inside with lead, which are fastened w T ith 
 screws having large flat heads, plated with lead. Besides 
 the steel plates have a number of small holes, through 
 which the air can escape when pressing against them. 
 
124 THE MANUFACTURE OF CELLULOSE. 
 
 After the boiler is charged and fed with leach of 5°B it is 
 heated by steam, so that the pressure gradually rises to 
 4.7 atmospheres. This pressure is kept up (while the di- 
 gester is rotating about 4 times per hour) until samples 
 show that the raw material is transformed into a pulp, 
 which as a rule requires about 8 to 9 hours time. After 
 boiling is finished, the contents are discharged into a cis- 
 tern of draining stones or perforated wooden walls ar- 
 ranged below the digester, and later on washed and disin- 
 tegrated. The presence of the acid phosphate of lime (see 
 leach making) is considered to prevent the stuff from be- 
 coming reddish in boiling. 
 
 A new American patent of Flodquist is described and 
 illustrated, under ~No. 525,540. 
 
 While until now sulphite stuff digesters were heated 
 either from inside by direct steam or from outside by 
 means of a steam jacket, whereby the former method 
 caused a disadvantageous and uneven dilution of the leach 
 and the latter on account of the high steam pressure re- 
 quired, made necessary a very strong and expensive jacket, 
 according to the present invention the digester is heated 
 from outside by means of hot air or hot gases, e. g., com- 
 bustion gases free from smoke of about 300 °C. Because 
 air does not need to be under pressure to be heated to the 
 required temperature, the mantel can be made of quite 
 thin sheets. Because the mantel does also not need to 
 be especially tight, it can be composed of single pieces, 
 which can easily be taken off, to lay free the digester. 
 
 The boiler A is resting with hollow pins, BB, in boxes 
 C, and is by means of the worm-wheel D and the worm 
 Dl made to rotate. A pipe L serves to test the inner steam 
 pressure. As usual, a manhole, N, is provided. The jacket, 
 to prevent radiation of heat, is hollow and filled with as- 
 bestos or mineral wood. The cylindrical body, E, of the 
 jacket is connected with the walls of the digester by the 
 angle-iron Gl and revolves like the right head-wall El to- 
 gether with the digester. Whereas the left head- wall, E2, 
 which carries the inlet H for the hot air or the hot gases, 
 does not y revolve. With the ring, e, it turns on the hol- 
 low shaft, B, and at Y it is supported against the middle 
 revolving part of the jacket. In the right head-wall are 
 arranged in a circle a number of holes, 0, leading to a fixed 
 hollow space, 1ST1. The hot air enters at the left through 
 
THE MANUFACTURE OF CELLULOSE. 
 
 125 
 
 the pipe H into the space between jacket and digester, sur- 
 rounds the latter and reaches through the openings, 0, in 
 
 Fig. 56. 
 
 the right-hand head wall the hollow space Nl, from which 
 it is carried off by pipe HI. 
 
126 THE MANUFACTURE OF CELLULOSE. 
 
 In concluding this chapter a few propositions are yet to 
 be mentioned in regard to construction and lining of sul- 
 phite digesters. 
 
 A Mr. Wagg in America;, like Mitscherlich, lines the di- 
 gester with thin sheets of lead, lays upon this asbestos pa- 
 per and upon this 8 inches thick of bricks of one foot 
 square. Every brick is then severed to the digester wall by 
 a bolt in such manner that the head is let into the brick 
 and the nut is put on outside. The bricks have furrows 
 all around, which by means of blunt tools are filled with 
 lead, swallow-tail-like and made tight with it. The heads 
 of the bolts are also covered with lead and the bolts them- 
 selves are flattened on one side, so that the acid alongside 
 of them through a cut-out in the nut, can go outside, 
 when the lining is leaking. It is thus, as in Frank's di- 
 gester, made possible to find out where a leak occurred in- 
 side and easily repair it. 
 
 In the sulphite digesters of Frambach and Dart in Kan- 
 kauna and "Vollrath in Shebaygan, Wisconsin (American 
 patent No. 348,159), where until now the sulphite stuff 
 digesters were provided inside with a lead lining, accord- 
 ing to the present invention an acid proof and elastic coat- 
 ing with enamel is employed. 
 
 The digester illustrated in fig. 57 consists of single 
 tubular sections provided with flanges and the head and 
 bottom piece B; the different parts are with their flanges 
 connected by screw-bolts. For the purpose of tightening 
 rings of lead, D, are laid between the flanges. All parts 
 mentioned are covered with enamel on the inside up to 
 part of the flanges. The digester is heated by a bent steam 
 pipe, E, which is provided outside with a coat of enamel. 
 For the air-tight connection of it to the bottom-plate ,B, 
 the lead-rings, I, are provided. 
 
 To coat the different parts of the digester with enamel 
 they are first treated with acid, then scrubbed with sand, 
 rinsed off, dipped into hot lime water and dried. The parts 
 are then wiped off with a sponge and the first coat of 
 enamel is put on. After this has dried, the pieces are 
 heated in a muffel until the melting of the enamel. After 
 cooling off, the second coat is put on and also dried and 
 melted. In enameling, any vitreous enamel which is acid- 
 proof and elastic can be used. A suitable mixture for the 
 first coat consists of 5 parts of lime, 10 parts of feldspar, 
 
THE MANUFACTURE OF CELLULOSE. 
 
 127 
 
 5 parts of carbonate of soda, 50 parts of white sand, 50 
 parts of lead oxide and 20 parts of boracic acid, which are 
 mixed and fluxed together, then ground and stirred with 
 water to a thin mass. For the second coat the above men- 
 tioned substances -can be employed, adding 10 parts of 
 bone-ash, 5 parts of talcum and 4 parts of cryolite, which 
 are mixed and fluxed together with great heat to a liquid 
 glass, poured into water (for granulations) ground very 
 fine and stirred up in water. 
 
 Fig. 57. 
 Lining for the sulphite digester of Goldburg Harden- 
 Pond in Eutland, Vt., (American patent 351,067) in place 
 of the lead lining used hitherto according to the present in- 
 vention, for boilers and other apparatuses, coming in con- 
 tact with acid, a bronze is used composed of 100 parts of 
 copper, 33^ parts of lead, 10 parts of tin and 4 parts of 
 antimony. This bronze is claimed to be very durable and 
 entirely resistant against the acids employed in producing 
 cellulose. 
 
12S THE MANUFACTURE OF CELLULOSE. 
 
 A greater novelty than the methods hitherto mentioned 
 is the employment of an acid-proof protecting mass, which 
 is offered by Wilhelm Wenzel, Vienna, and which is claim- 
 ed to have proved practical. According to this method 
 the protecting mass is put on in liquid form with a pat- 
 tern of boards, and according to size and form of the di- 
 gester, about 60 to 100 millimeters thick. In Mitscherlich 
 boilers of 4 meters diameter the thickness amounts to 125 
 millimeters. At the bottom the coat must be heavier and 
 rounded towards the cylinder. Revolving digesters of 2% 
 to 3 meters diameter require a coat of 80-100 millimeters, 
 while for those of 2 to 2-J meters diameter, 70 to 80 milli- 
 meters thickness are sufficient. The work requires 3 to 4 
 weeks. When completed the lining of the digester is ex- 
 posed for several hours under pressure to a temperature of 
 110 to 150°C. This causes cracks, which are cut open and 
 again covered with the mass. This is repeated, until no 
 more bad places show up and for finish a coat of 4 to 5 
 millimeters thickness of very fine mass is applied. Accord- 
 ing to experience this last coating is used up in 2 to 3 
 months, but can be easily replaced with a brush in one 
 hour by two men, and after two more hours the digester 
 can be used again for boiling. The 4 to 5 millimeters of 
 used-up coating certainly goes into the stuff, but does 
 not do any harm, it is claimed. As the principal ad- 
 vantage is pointed out, that the boiler always remains tight 
 and the sulphurous acid can never get near the boiler shell. 
 The coat of this method amount to 70 marks per square- 
 meter surface to be lined, where to have yet to be added 
 freight, wages, etc. This method is therefore not cheap, 
 but if given absolute protection, it would be a welcome 
 substitute for most of the methods hitherto employed. 
 
 Later on Mr. Wenzel has made several changes in the 
 manner of lining digesters. He does not employ leaden 
 braces, but such of phosphor-bronze, because such do close- 
 ly bind with the mass. The safety screws of the lead-lined 
 boilers are done away with and are substituted by just as 
 many small open control holes, which permit the lining 
 to be seen from outside. The application of the mass is 
 done slowly and layer by layer, and strong iron wire is laid 
 in crosswise, so that these, similar to the Monier method 
 in building, form an iron skeleton, giving to the whole 
 mass much strength in holding together. The whole layer 
 
THE MANUFACTURE OF CELLULOSE. 129 
 
 is finally about 10 centimeters thick, and lastly porcelain e 
 tiles are laid in, then slowly heated and the furrows occur- 
 ing are always coated again with cement, until the lining 
 does 'not change any longer. Later occuring tears and 
 faults are repaired in the same manner. The composition 
 of the mass is secret, but it may be said that cement and 
 water-glass form important constituents of it. A special 
 value of the described lining is in the saving of fuel. The 
 quantitive determinations of the heat used shows that 
 the lining forms an excellent protector of heat; the radi- 
 ating heat is thus reduced to a minimum. The deter- 
 minations resulted a saving of 25^ of heat as against a 
 digester lined with lead. 
 
 A revolution in the making of digester linings seems 
 to be caused by the invention of Herr Director Brungger 
 in Cunnersdorf, as thereby a rapid, entirely safe and very 
 cheap method is given, which has already proved to be 
 practical in many years use in several factories. The es- 
 sence of the patented invention consists in producting a 
 thin, impenetrable crust at the inner digester wall by 
 introducing a sulphite leach, a sulphate of lime solution 
 into the boiler, previously heated from outside and charged 
 with wood. This crust prevents every contact of the metal 
 boiler wall with the sulphurous acid and used in boiling and 
 thus protects the digester against the destructive influence 
 of the sulphurous acid. 
 
 With the protecting means used until now, the lead 
 lining and the many methods of lining with bricks could 
 be provided only at the expense of time and money, the 
 formation of the protecting crust costs neither time nor 
 money. When the protecting crust is once formed it never 
 requires repairing and even a renovation of it seldom be- 
 comes necessary. 
 
 In employing linings of lead and bricks of any kind the 
 digesters are withdrawn from use during making and re- 
 pairing of the protecting lining. 
 
 In the digesters at Cunnersdorf, near Hirschberg, for 
 instance, while they had the lead lining, about 210 opera- 
 tions were made per year (the balance of the year was used 
 in repairing the lead lining,) against almost 300 opera- 
 tions, after they were provided with the protecting crust. 
 In the figures the renovation of the lead lining is not 
 taken into consideration. The producing capacity of a di- 
 
130 THE MANUFACTURE OP CELLULOSE. 
 
 gester with protecting crust is according to this almost 
 one-half larger than if provided with a lead lining. 
 
 The inventors mark another advantage, the cessation of 
 the damaging to the boiler, connected with the leaking 
 of the linings of lead or bricks, as well as the rapid using 
 up caused by this, and the possibility of an explosion. The 
 crust is entirely impenetrable, adheres firmly to the di- 
 gester, but can be taken off in a few hours and just as 
 quickly renewed. The inventors have after about one year's 
 work of the boiler removed the crust and at the inspection 
 of the inner digester wall by the officials of the society for 
 boiler revision it was found that no corrosions whatever 
 could be discovered in the digester walls. After working 
 four months longer it has been settled by other eminent 
 experts in the same way, that the iron mantel was without 
 fault and the iron appeared as if it had come directly from 
 the rolling mill. The digester provided with the protect- 
 ing crust therefore offers greater security in working, 
 which is increased by the fact that it works with very lit- 
 tle over pressure. The digesters also work with much less 
 consumption of steam, because in consequence of the inter*- 
 mittent work they never get cold. 
 
 Against other linings the crust produced by sulphite 
 leach offers the advantage that during boiling it completes 
 and renews itself, if cracks or holes should occur, that 
 consequently it always remains fresh and complete. The 
 heating from outside by steam jacket also permits easy 
 regulation of temperatures and prevents increasing dilu- 
 tion of the leach, produced by the introduction of direct 
 steam. 
 
 To the above mentioned experts also belongs Professor 
 Eeuleaux, who settled that with the protecting crust as a 
 rule 2 to 3 millimeters thickness is really a protection for 
 the digester itself, because his testimony says that the 
 iron surface, becoming free under the layer, has proved 
 to be entirely free from rust and pores. Nowhere in the 
 whole inside wall not a spot eaten by the acid could be 
 discovered. 
 
 In America the method has already been introduced. Not 
 only rotating digesters, but every horizontal or upright di- 
 gester as well may be provided with the protecting crust, 
 if but a heating jacket around the digester is provided, as 
 the crust inside can only be produced by heating from out- 
 
THE MANUFACTURE OF CELLULOSE. 131 
 
 side. The stuff produced in such digesters is claimed to be 
 better and stronger, because the sulphite leach in them re- 
 tains its original strength and is not diluted by condensed 
 steam. This has value only in regard to boilers, in which 
 formerly boiling had been done by direct steam. 
 
 For Brungger's method not only solution of bisulphite 
 of lime, as prepared in the production of cellstuff from 
 wood according to the sulphite process, are suitable, but 
 also solutions of sulphate of lime, sulphite of lime, sulphite 
 of strontium and diverse others. When using a solution 
 of bisulphite of lime, sulphite of lime is next separated 
 from the hot digester wall, which by further action of 
 the heat is decomposed into sulphate of lime and sulphite 
 of lime, under liberation of water, sulphurous acid and 
 sulphur. When a solution of sulphate of lime is used, 
 it is advisable, to. prepare it by neutralization of a weak 
 sulphuric acid solution with carbonate of lime. The de- 
 gree of concentration of the solution is of no consequence 
 for the success of the method, neither does it matter 
 whether the digester wall is heated before or after charg- 
 ing the solution. When producing cellstuff according to 
 the sulphite-process it is advisable, when working with 
 dilute solutions, to charge it together with the wood 
 into the cold digester and then to heat it. With concen- 
 trated solutions this can not be done, as the solution will 
 attack the digester wall too much, before the protecting 
 crust has formed. In this case the empty digester is first 
 heated from outside, the solution then let in and the digest- 
 er set in rotation, until the crust has sufficient thickness. 
 The wood is charged thereafter. If a revolving digester is 
 used it does not need to be entirely filled; a fixed digester, 
 however, must be completely filled with the solution and be- 
 sides, next to the digester a vessel should be placed, into 
 which part of the solution can flow over, when the solution 
 expands in consequence of the heating. The heating of the 
 digester can either be done by means of a steam jacket or 
 the boiler may be placed in a chamber of brick, through 
 which are conducted the gases from a fire. 
 
 A method for producing a lining for cell-stuff digesters 
 was patented by Guido Baerwaldt in Germany under No. 
 70,477. This digester on its inside is freed of oxide and 
 other impurities by boiling with acid and scrubbing and 
 then coated with a layer of cement, diluted with water,.. 
 
132 THE MANUFACTURE OF CELLULOSE. 
 
 potash or soda lye, waterglass, or lime milk, to the thick- 
 ness of some centimeters. The cement used may be either 
 entirely pure, or mixed with clean quarz sand, powdered 
 glass, ground charmotte or similar substance. Before the 
 ground layer of cement has settled, it is well ground up 
 with a pasty mixture of oxide of lead and glycerine, this 
 last layer being permitted to cover the cement layer to a 
 certain thickness. 
 
 The lining thus prepared hardens after standing for a 
 while and forms a vitreous, very hard and resisting crust, 
 which prevents the penetration of the sulphite solution and 
 thus makes the digester very capable of resisting and very 
 durable. 
 
 The mixture of lead-oxide and glycerine can also be ap- 
 plied directly to the clean metallic digester wall, but the 
 application is then some more difficult" than upon a pre- 
 vious ground layer of cement. The mixture described can 
 also be employed as binder or as mortar when lining the 
 inner boiler wall with acid proof bricks or tiles. 
 
 According to the letters of the American patent No, 
 514,197 of E. Meurer of Palmer Falls, N. Y., the metal of 
 the sulphite digester can be completely protected against 
 the action of the leach by a coating of red oxide and 
 glycerine. The inventor recommends 100 parts of thor- 
 oughly dry oxide of lead ground up with 12 parts of pure 
 glycerine and that the coat be made about one-third cen- 
 timeters thick. The mass must be used up quickly, be- 
 cause it soon hardens into a stone-hard and well-adhering 
 cement. By adding more glycerine the mass becomes more 
 plastic, but dries slower. When desired to further protect 
 the coat by a lining of bricks inside of the digester, the 
 same mixture can be used as mortar and it becomes almost 
 as hard as the stones themselves. 
 
 The same inventor describes in a second patent a method 
 of lining the digesters with lead. The sheets of lead are 
 laid against the inner wall of the digester and the edges 
 are soldered together, so that the whole lining forms a 
 single piece, closely adhering to the boiler Wall. Because 
 the lead lining is not connected with the digester wall by 
 rivets or cement it will not be influenced by the expan- 
 sions and contractions of the- boiler wall with changing 
 temperatures. But it must be protected by an inside wall 
 
THE MANUFACTURE OF CELLULOSE. 123 
 
 of fireproof stones against falling in when discharging 
 the digester. 
 
 While lining with lead the digester is practically 
 brought into a horizontal position. The sheets of lead, 
 when laid against the wall are held fast by a frame with 
 arms and pins. 
 
 After all sheets of lead are put in and by soldering to- 
 gether the edges are united into a whole, the digester is 
 placed vertical and the brick lining is then built up. As 
 the wall rises, the pins and supports are gradually removed 
 and finally also the middle beam of the frame. 
 
 Another invention, to make the digesters acid-resisting, 
 is by Henry W. Stebbins in West Carrollton, Ohio (Ameri- 
 can patent 528,339), is as follows. 
 
 The overlapping sheets of the boiler wall, to procure a 
 smooth inside face, are provided with a layer of Portland 
 cement, upon which the lead lining is to lay. The lead 
 lining is fastened by lead-rivets, reaching through holes 
 in the digester shell and in the layer of cement and the in- 
 side is soldered together with the lead sheet. Upon the 
 lead lining goes a layer, consisting of a poor conductor of 
 heat, such as Portland cement with asbestos, with an ad- 
 mixture of lamp-black, sulphate of barium, oxide of lead 
 and waterglass, to make the porous layer of cement and 
 asbestos resistant to acid. A suitable proportion is given 
 in the letter of patents. As 10 parts of sulphate of barium, 
 8 parts of oxide of lead, 2 parts of lamp-black and a solu- 
 tion of waterglass of 12° Ee. Then follows, built in with 
 cement, a layer of hard burned porous bricks, formed un- 
 der hydraulic pressure. The next layer consists of Port- 
 land cement and quarz sand, lampblack, sulphate of barium, 
 oxide of lead and waterglass again mixed in. It 
 should have the consistency of mortar and is poured be- 
 hind the innermost layer of glazed tiles. 
 
 In England instead of cement for the tiles a. plastic mass 
 made of asbestos and waterglass of 1.5 spec. grav. is used, 
 serving to close up the joints. 
 
 N. P. W r edege of Drontheim, had patented in Germany 
 under No. 78,966, a discharging arrangement on fixed 
 cellulose digesters and says the following about it: 
 
 Until now in discharging the digester the acid was gen- 
 erally first let out by a special pipe attachment, then the 
 upper cover was opened and the digester filled with cold 
 
134 THE MANUFACTURE OF CELLULOSE. 
 
 water to- wash the 1 mass and to cool off the digester when 
 the mass was shoveled out by hand. By this process the 
 digester is exposed to sudden and repeated changes of 
 temperature, which has a damaging effect on material and 
 lining, and besides causes a direct loss in heat and time, 
 when the digester is to be filled again. 
 
 Often, also, the digesters were' discharged by rinsing 
 with water, but in this the changes of temperature have 
 also had an injurious influence, and then a large supply 
 of water was always necessary. Finally the blowing out of 
 the digester by means of the inner steam pressure was 
 employed; but the inconveniences are perhaps greater in 
 this method than in the former. During emptying a 
 vacuum is charged and the consequence often was that 
 the inner linings were injured. Besides the undissolved 
 knots, etc., were crushed, whereby the stuff was soiled. 
 
 The hereafter described method aims to empty the di- 
 gester by its lower manhole, which by means of a mechan- 
 ism, specially built for the purpose and by the steam 
 pressure conveniently discharges from the digester stuff 
 and liquid. The mixture is then conducted to the stuff- 
 basin, where it is effectively sprinkled with water, so that 
 the badly-smelling leach is mixed with pure water and runs 
 off through the outlet-pipe. The peculiarity of the dis- 
 charging arrangement is that the lower manhole can be 
 conveniently opened by an arrangement, provided at the 
 upper manhole. 
 
 In fig. 58, a is a plate, lying against the edge of the neck 
 of the lower manhole. During boiling this plate is pressed 
 tightly against the cover, b, partially by the pressure pre- 
 vailing in the digester, and partially by a screw let through 
 the movable guard bl. The plate, a, is by the rods, a2, 
 also connected with a sieve, c, lying against the inner lin- 
 ing, d. By this means an open space, e, is formed for 
 the steam, which during boiling enters through, f, and 
 usually serves to heat the charge of the boiler. The rods, 
 a2, above the sieve form eyes, by which they are connect- 
 ed by joints, a3, with a larger ring, g. This ring, g, is 
 hung to a rod, h, which is joined to a spindlescrew, h2; 
 the latter goes through the upper manhole. The upper 
 manhole cover, i, is provided with a hole in the middle, 
 over which is a collar or hull, j, upon which rests a large 
 nut, kl, by means of which the spindle, k2, can be moved 
 
THE MANUFACTURE OF CELLULOSE. 
 
 125 
 
 up and down. When the digester is working and there- 
 fore the screw is not used, this nut is covered by a cap 
 and this again is secured by a smaller nut, k2, screwed 
 on the shaft, h2. All parts inside of the digester are 
 
 Fig. 58. 
 
 covered with lead for protection against the action of 
 the leach or are made of an acid proof material. After 
 boiling is finished the discharging is done in similar 
 
136 THE MANUFACTURE OF CEUL.ULOSE. 
 
 manner: First the gas is blown off, for instance through 
 the opening, ml, of the upper manhole, then the lower 
 guard, bl, is loosened and after removing the nut, b2, is 
 taken off. During this work the plate, a, is held suf- 
 ficiently tight by the pressure in the digester. In place 
 ■ of the guard, b, a piece of pipe is then set in and fastened 
 by rest screws. This piece of pipe connects the digester 
 with a stuff basin below. Then steam is admitted by 
 means of a perforated pipe, through the opening, m2, 
 above the plate, a, which goes through the digester in sev- 
 eral windings, and finally by turning of the nut, kl (laid 
 free by taking off the cap), the whole lower locking-ar- 
 rangement is lifted up into the digester. The continuous 
 incoming steam makes the creation of a vacuum impos- 
 sible, and by causing the whole charge to move, stuff 
 and acid flow through the attached piece of pipe into the 
 stuff -basin. 
 
 The whole operation goes on conveniently and safely, 
 and the great advantage is gained of keeping the digester 
 warm, and retaining all gas for the next operation. At 
 the same time the stuff runs out quickly and evenly, with- 
 out getting soiled. When all stuff is removed from the 
 digester, the steam is shut off and plate, a, is screwed 
 down again in its place. To fill the digester again with 
 wood the upper manhole must be opened. For this pur- 
 pose the nut, kl, is altogether screwed off the spindle, h2, 
 and this, by means of a chain, hooked into the upper 
 ring, h3, is, together with the shaft, hi, let down into the 
 vessel, until a wedge pushed for this purpose in the spin- 
 dle, h2, comes to rest upon the cross piece, h5, arranged 
 at the upper manhole. The manhole cover, i, is then re- 
 moved and the digester is filled. When this is done, i is 
 put on and the shafts, hi and h2, are lifted and secured. 
 
 In regard to the armatures of the digester, the bushings 
 and valves are at present mostly made of phosphor bronze 1 , 
 which offers the most resistance to the acid leaches. Other 
 resistant material may, however, be employed, as for in- 
 stance C. Curtis and N". M. Jones in Massachusetts and 
 Maine had an outlet pipe for sulphite digesters patented 
 in America, which is claimed to answer the same purpose. 
 According to their statements an iron outlet pipe, lined 
 with cement and protected at both ends by rings of a 
 metal is not attacked by the acid leach. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 137 
 
 Fig. 59 shows the iron pipe, a, with the flanges, al and a2. 
 Upon the lower flange is screwed a ring, a3, of lead or 
 phosphor-bronze, protecting inside and forming an inside 
 flange. Into this pipe is pushed one or more pipes, b, 
 pressed out of a mixture cf Portland cement, quartz and 
 waterglass. When several pipes are used, the joints are 
 cemented when put in. The cement pipe has a somewhat 
 smaller diameter than the inside of the iron pipe, so that 
 between both pipes a ring-like hollow space is left. By 
 
 /BE 
 
 <V 
 
 
 strips, e, of wood pushed between the cement pipe is given 
 a concentric position to the outer-pipe, as shown in fig. 
 60, representing a section through the line 4-4 of fig. 
 59. After the cement pipe is built up to the top the 
 hollow space between both pipes is filled out with cement, 
 al the same time the strips of wood are drawn out and 
 the upper end is protected by an acid proof ring, a4 
 (fig. 59). 
 
 In conclusion it may be mentioned that the just de- 
 scribed digesters of the different methods are no longer an 
 
138 THE MANUFACTURE OF CELLULOSE. 
 
 indication of the cellulose produced by a factory, because 
 the instructions of the different inventors have been modi- 
 fied to suit local conditions by the manufacture, or changed 
 for other reasons. So for instance was the digester in the 
 Kitter-Kellner factories originally taken for but 30 cubic 
 meters capacity. Now in several such factories digesters 
 of 40 and 60 meters capacity can be seen; indeed the author 
 has seen in one of them horizontal boilers of even 100 cubic 
 meters capacity, externally not at all differing from the 
 Mitscherlich digesters, but provided inside with other lin- 
 ings and having direct steam heating. The Mitscherlich fac- 
 tories have also adopted the new method of dressing the 
 wood, as well as the Frank leach making method, and also 
 employ the new disintegrators, 
 
 C. PKODUCTION OF CELLULOSE BY MEANS OF 
 THE ELECTEIC CUKKENT. 
 
 About this new method nothing more has been publish- 
 ed than is contained in the letters of patent, as printed 
 in the Papier Zeitung. Whether this method will ever 
 cause a practical revolution in the manufacture of cellu- 
 lose, can not yet be judged. For the sake of completeness, 
 this new result of the industriousness of Herr Karl Kellner 
 may be described as follows: This method is based on the 
 application of the electric current for the production and 
 continuous regeneration of substances during boiling, de- 
 composing and the incrusting substance of the wood. The 
 wood is heated, while the electric current is passing 
 through at the same time, with such liquids or solutions 
 as under the influence of the latter, furnish those means, 
 which act decomposingly on the incrusting substances. 
 
 For this the solution of the chlorides of metals are suit- 
 ed and especially that of sodium chloride, as the incrust- 
 ing substances of wood, straw, espartos, etc., are decom- 
 posed by chlorine, as well as by certain of its oxygen-com- 
 binations, such as subchloric acid (hydrogen hypochlorite). 
 
 When the vegetable matter to be decomposed in desin- 
 tegrated condition are heated in closed vessels with solu- 
 tions of sodium chloride and at the same time an electric 
 current is passed through the solution, chlorine and sub- 
 chloric acid are produced at the one side and hydrate of 
 soda at the other, the elements, chlorine and sodium, lib- 
 
THE MANUFACTURE OF CELLULOSE. 139 
 
 erated at the poles (electrodes), forming with water sub- 
 chloric acid and hydrate of soda. 
 
 In decomposing the inerusting substances by chlorine 
 and subchloric acid, as well as when heating subchloric 
 acid by itself, hydrochloric (muriatic) acid is formed, which 
 in contact with sodiumhydrate reproduces sodium chlor- 
 ide so that a circulation takes place, and the same liquid 
 runs through the whole process unweakened. 
 
 The process goes on smoothly at 128° C and according 
 to the statement of the inventor at that temperature a 
 snow-white, unweakened fibre of silky gloss is obtained 
 from wood. 
 
 In working this method an arrangement is used consist- 
 ing of three vertical digesters, connected on top and 
 below, lying in one plane. Both electrodes enter the outer 
 pipes below and into side pipe, in which both electronega- 
 tive iones (chlorine and subchloric acid) are rising during 
 heating, is filled the vegetable material. The liquids con- 
 taining the iones and its products of decomposition rising 
 during heating, and meet above, thereafter descending 
 through the middle pipe. When passing the electrodes 
 decomposition of the chlorides takes place again. Very 
 good results can be obtained in this arrangement by 
 changing the current, whereby the second side branch is 
 filled with wood, etc. The vegetable matter is then at- 
 ternately submitted to the treatment with alkaline and 
 acid solutions. The soda lye formed thereby acts decom- 
 posingly on the inerusting substance in such manner that 
 they are quickly dissolved when the current changes. To 
 produce, for instance, white cellulose for the manufacture 
 of paper from pine wood, the wood disintegrated by the 
 usual wood choppers is charged in to the digester and the 
 latter closed, whereupon chloride of sodium solution is 
 let in. In general on 8$ solution suffices and about 3^ 
 hours at a temperature of about 126°C is required (count- 
 ing from the point of the temperature reached) to produce 
 from pinewood, white, firm cellulose which can be used 
 for finer papers. 
 
 The boiling itself is done in vessels, the inside of 
 which is lined with lead or other resisting substances. The 
 following well proven arrangement (fig. 61) consists of 
 both fixed digesters A and B, which are connected below 
 by the pipes I, above by the pipes H, and provided with 
 
140 THE MANUFACTURE OF CELLULOSE. 
 
 charging opening E and below with discharging open- 
 ings. Perforated plates at the upper and lower ends 
 prevent the fibres 1 from being carried along by the cur- 
 rent and clogging the pipes. The two pipes H make con- 
 nection with a smaller intermediate vessel L, which carries 
 gauge-glass, macrometer, safety-and discharging valve and 
 a pipe T, which can be shut off by valve V, the prolonga- 
 tion of which forms a coil, lying in a cooling tank P. The 
 vessel L ends in pipe K, which leads below the bottoms of 
 the digester and then runs out into fork-like branchings I, 
 which turning up at both sides, run into the bottoms of 
 the digesters. Into these pipes at M and N the two carbon 
 electrodes, E and S, are introduced insulated. After the 
 digesters are filled with wood and a solution of chloride 
 of sodium is let in until it becomes visible in the gauge- 
 glass of the vessel L, valve V and all openings are closed, 
 into the heating pipes running through the digesters, and 
 steam, as dry as possible, is admitted. 
 
 Because the contents of A and B are expanded by the 
 heat, they rise through H into L, thus causing a descend- 
 ing current through pipe K. When leaving K the liquid 
 divides and rises again in the direction of the arrow 
 through pipe I, to enter again into the digesters A and B, 
 and to repeat this circulation. In passing of the liquid at 
 the electrodes, when the current is closed the decom- 
 position commences and the before mentioned side-pro- 
 cesses take place. When at M the positive, at N" the 
 negative current is entering, the incrusting substance of 
 the wood contained in B is submitted to energetic oxida- 
 tion on account of the action of the chlorine or its de- 
 rivatives, while in A the resins existing in the wood, con- 
 tained in there, are saponified. The products of decom- 
 position (as far as they are soluble) meet in the vessel L and 
 act upon each other in such manner that as end-product 
 chloride of sodium is formed again, the hydrochloric acid 
 formed at the anode decomposing the organic compounds 
 coming from the cathods and separating the organic mat- 
 ter, regenerates the original solution of chloride of lime, 
 while the separated organic matter by the continuously 
 renewed influence of the chlorine and its combinations is 
 decomposed into products, which either remain in solu- 
 tion or escape in the form of gas. 
 
 After the process has been conducted in the manner de- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 141 
 
 scribed for about one-quarter to one-half hour, the cur- 
 rent is changed. Thereby by the alternating influence of 
 chlorine and soda upon the wood its dissolution is quick- 
 ened. Therefore, the changing of the current is repeated 
 often, until the fibre is laid bare, which at a temperature 
 of the leach of about 126 °C is affected after 3 to 3^ hours. 
 The inactive gases evolved during the operation, which ac- 
 cumulate in the intermediate vessel L are by the occa- 
 
 Fig. 61. 
 
 sional opening of the valves V driven into the cooling 
 and condensing apparatus. 
 
 When the work is carried on in the manner described 
 above, snow-white cellulose is obtained from the vessel, 
 which at the end of the process had the unode under it, 
 and this can be used for the finest sorts of paper without 
 bleaching, while the product from the cathode vessel is 
 colored somewhat yellowish by the alkali formed at the 
 end of the process, and after washing needs to be treated 
 with a very weak solution of chloride of lime. 
 
142 THE MANUFACTURE OF CELLULOSE. 
 
 Eepeated experiments have proved that it is of great- 
 er advantage not to treat the wood any more in metal ves- 
 sels, but in open cisterns of masonry, consequently to work 
 without pressure. The cisterns consist of cement mason 
 work and are lined with burned clay tiles. The cut wood 
 is soaked with a salt solution before filling it in the cistern. 
 The electric current produced by dynamo machines and 
 conducted through the mass evolves from the salt chlorine 
 and sodium, which accumulate at the poles and act partial- 
 ly dissolving, partially bleaching. By pressing a button 
 the current is from time to time reversed, so that the 
 sodium goes to the pole, where previously chlorine had 
 accumulated, and the chlorine to the pole, where before 
 soda had appeared. By this changing treatmnet with soda 
 and chlorine the wood suffers complete dissolution and 
 bleaching, and the chloride of sodium is continuously re- 
 generated. 
 
 At a most convenient site in Hallein, near Salzburg, 
 reputed for its strong brines, Herr Kellner has already 
 made a plant on a large scale, according to his latest 
 system. 
 
 Now, after four years, a conclusive opinion cannot yet 
 be passed about Dr. Kellner's process to produce cellu- 
 lose by means of the electric current, at least in a perfect, 
 practical shape. The inventor himself has authorized the 
 writer to make the following statement about the present 
 stand: The electrolytic cellulose manufacturing method, 
 as such, on a smaller scale, works quite well, but until now 
 it could not be introduced into large practice, because the 
 apparatuses of the decomposition cells required so many re- 
 pairs that the advantage offered by the process were 
 counterbalanced. Dr. Kellner has for this reason left the 
 process entirely for some time, and set himself especially 
 to the improvement of the electrolytic parts of the ap- 
 paratus; he has succeeded in this to such a degree that he 
 has accomplished the most difficult part of the industrial 
 electrolysis, i. e., the spitting of common salt into its 
 components, practically on a large scale, so that already 
 two large soda and chloride of lime factories in England, 
 are almost completely filled up accordingly and also in 
 Austria such an establishment is going to be built. These 
 experiments and labors made in other directions have not 
 directly benefited the electrolytic cellulose manufacturing, 
 
THE MANUFACTURE OF CELLULOSE. 14a 
 
 but have removed these difficulties, which until now were 
 in the way of the industrial employment of the electro- 
 lytic cellulose process and now soon after finishing the 
 plants designed for this purpose the experiences gained 
 will be of value in the manufacture of the electro-cellu- 
 lose. The electric process itself, as said before, is excellent,, 
 the paper made of such cellulose is very solid and pure. 
 To work the process, however, especially in regard to the 
 choosing of materials was, until the electrochemic soda 
 and chlorida of lime process were worked out, too expen- 
 sive. The question as to the practical value of the method 
 must therefore be left open for some time. 
 
 In connection with this it may be mentioned that Herr 
 Kellner had also patented the electric bleaching method 
 as such and indeed "La Papeteric" in France describes this 
 as follows: 
 
 "The process in bleaching vegetable fibre, which is the 
 object of this patent, is based upon the observation that 
 the coloring substances adhering to the fibre are by the 
 alternating application of chlorine and alkalies easier 
 transformed into water-soluble combinations, than by 
 chlorine alone. This occurrence is caused by the chlorine, 
 before transforming the coloring substances into water- 
 soluble combinations, causing the formation of intermedi- 
 ate products, insoluble in water, but soluble in alkalies. 
 When, therefore, after the intermediate products are trans- 
 formed into an alkaline solution, the chlorine is acting 
 again, not only chlorine must be saved, but the bleaching 
 must also be affected in less time. 
 
 The saving of chlorine and time will be the more as in 
 the ordinary chlorine bleach hydrochloric acid (muriatic 
 acid) is formed, and therefore the action of the chlorine 
 must be kept up, until acid-soluble combinations take 
 the place of the water-soluble combinations. 
 
 According to "the present invention an alkali-chlorine- 
 combination is decomposed by electrolysis. Thereby the 
 electronegative and the electro-positive products of de- 
 composition (Anion and Kathion) are alternately conduct- 
 ed through two separate quantities of the bleaching liquid r 
 then united and again taken to the electrolytic apparatus. 
 
 The arrangement may, as in fig. 62 and 63, have the 
 form of a double bleaching hollander, or, as in fig. 64, that 
 of a tub or of two separate bleaching hollanders. 
 
144 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 The hollancler represented by fig. 62 in plane and by 
 fig. 63 in section is by a wall aa through the length divided, 
 in three compartments. The fibre stuff to be bleached is 
 by pump d carried to the middle space. It flows along the 
 sieve-like perforated bottom and at the end of it gets under 
 the paddle-wheel f, which is in continuous motion. By 
 this it is taken up and driven to the side compartments 
 cc. In one of these compartments the electro-positive de- 
 composing solution is through the perforated pipe g ad- 
 mitted to the mass to be bleached, while in the other com- 
 partment the electro-negative works through a similar 
 pipe g. The bleach-stuff flows upon inclined bottoms 
 
 Figs. 
 
 62-63. 
 
 through the side compartments to their lowest place lay- 
 ing near the original inlet and there runs through the 
 openings cc into a reservoir, from where it is again carried 
 to the middle space by the pump. 
 
 Meanwhile the two iones have united again, the regen- 
 erated decomposing liquid accumulates under the sieve c, 
 and by the pump i, and it is returned to the electrolytic 
 apparatus j, through the pipe r. There^ before it reaches 
 the electrodes, of platinum , carbon or zinc, it flows through 
 a sieve j2. 
 
 The jointed anodes and cathodes are at its upper parts 
 
THE MANUFACTURE OF CELLULOSE. 
 
 145 
 
 separated by short divisions ]3 and the so formed com- 
 partments open below, are alternately connected with the 
 one or the other of the pipes gl gl, which are arranged 
 along both sides of the compartment j. In consequence 
 of this arrangement, the one pipe conducts electro-positive, 
 the other electro-negative decomposing liquid into the con- 
 necting pipes gg. 
 
 When the electric apparatus is to be connected with 
 two separate bleach hollanders, the bleach mass in both 
 of them is kept in continuous motion by suitably arranged 
 pipes, and wash drums return the decomposing liquid to 
 the apparatus. In this case the direction of the electric 
 current must from time to time be changed so that the 
 
 * L 
 
 Fig- 64- 
 
 fibres to be bleached are alternately submitted to the 
 action of chlorine and alkali. 
 
 This changing of the direction of the current is also 
 requisite, when the apparatus is built as in fig. 64. The 
 bleaching process here takes place in two cylindrical tubs 
 with threefold partitions in each. The mass of fibre to be 
 bleached is introduced in the innermost space A of the 
 tub and there kept in continuous ascending motion by 
 means of a propeller screw p. set into the bottom. The 
 
146 THE MANUFACTURE OP CELLULOSE. 
 
 stuff flows over the walls m into the hollow space between 
 m and n and, following the current caused by the screw, 
 enters again into the inner space through the trapeze- 
 shaped openings ml in the bottom. 
 
 The circulation of the bleach mass could also take place 
 in reversed direction. It would then be driven out by 
 the openings m, rise up between m and n and return over 
 the edge of m. 
 
 The electro-positive decomposing liquid (Anion) enters 
 through the pipe f into the hollow space H. The lower 
 face of this hollow space is solid and tight, the upper 
 is sieve-like, perforated and covered with filter stones, so 
 that the anion filling the space H can come in contact with 
 the bleach stuff. 
 
 The electric-negative decomposing liquid (cathion) 
 enters into the like bottom of the other bleach tub. Both 
 liquids flow through the bleach mass from below upwards, 
 enter through the sieve-like upper part of the walls nl into 
 the space between n and o and from there flow through 
 the pipes g into the reservoir q. By the uniting of both 
 liquids, taking place there the solution, having been sub- 
 mitted to decomposition, is regenerated and again con- 
 ducted to tbe electric decomposition apparatus. Both tubs 
 are provided with water and air-tight covers 01, at which 
 openings 03, with blow-off-valves are arranged. These open- 
 ings permit the taking from time to time of samples and 
 the controling of the bleaching process. The pipes r 
 serve to admit steam and to heat the mass. 
 
 In place of two tubs whole rows of them can be used 
 and connected with each other by pipes, as it done simi- 
 larly with the diffusion batteries in sugar factories. In 
 such manner continuous work is possible. 
 
 About an improvement of his electric bleaching method 
 Dr. Kellner writes in the Papier Zeitung set 1894, page 
 2,486, as follows: 
 
 As easy as the decomposition of a solution of common 
 salt into chlorine and sodium by the electric current takes 
 place, and notwithstanding the numberless experiments 
 made it has not become possible until recently to find out a 
 method which has prospects for practical success. 
 
 The older methods failed principally on account, of too- 
 rapid consumation of the complicated apparatuses and of 
 tbe insufficient transformation of the required motoric- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 147 
 
 power into electro-chemical work. Siemens & Halske in 
 Vienna have now come forth with methods different from 
 those of Dr. Karl Kellner, which for simplicity leave 
 nothing to be desired. The following illustrations repre- 
 sent the Kellner method for bleaching of paper stuff. 
 
 Fig. 65 shows the so-called bleach-block. It consists 
 of the plates A, Al, A2, at one side covered with platinum, 
 which by the rods, B, Bl, B2, are united into one solid body. 
 When such block is set in a hollander and connected with 
 
 the clamps of a dynamo machine, the stuff in the holland- 
 er is at once bleaching, after adding solution of salt. The 
 stuff is continuously passing- between the plates. A, Al, the 
 electrodes and can therefore be bleached with little power, 
 as the chlorine evolved from the salt is acting in status 
 naseendi, the much more powerful state of creation, as 
 well-known. Fig. 65 shows a hollander with two of the 
 blocks described. The salt solution is continuously used 
 over again, and by adding fresh salt, kept at the original 
 
148 . THE MANUFACTURE OF CELLULOSE. 
 
 strength. By the decomposition of 20 kilogrammes of 
 salt, 100 kilogrammes of stuff are claimed to be bleached; 
 what kind of stuff is meant is not stated. 
 
 When several bleach-hollanders are placed in one room, 
 the method represented in fig. 66 is recommended, in 
 which for cheapness no platinum is used. Fig. 66 shows 
 the electrolytic apparatus in section and plane, the elec- 
 trodes consist of carbon; they are claimed to be cheaper 
 and more durable. The salt solution flowing into the ap- 
 paratus through the pipe, visible to the left above and pro- 
 vided with a valve, must find its way to B, as indicated 
 by the arrows, between the electrodes, arranged alternately, 
 forming a number of cells. As visible in fig. 66, the hypo- 
 chlorite-solution produced in the apparatus mentioned 
 from the salt solution flows at B through the filter F below, 
 of glass wool into the bleach hollander. If instead of 
 carbon, platinated plates are employed, the filter can be 
 dispensed with. The drain-box K serves to receive the 
 bleached stuff; the off-running salt solution is accumulat- 
 ing in L and after closing the valves h and h3 and opening 
 hi and h2, is by the pump P used for rapid filling of the 
 hollander when charging fresh material. The valves hi 
 and h2 are then closed, h and h.3 opened and by the pump 
 a steady circulation of the salt solution through the elec- 
 trolyser filter and hollander is affected during bleaching. A 
 further improvement of the Kellner bleaching method is 
 spoken of in the Centralbladt fur Oesterr Ungar Papier 
 Industrie, from which is taken the following: 
 
 In the decomposition of common salt by the electric 
 current, without using a diaphragm, the products of de- 
 composition, chlorine and caustic soda, unite in to sub- 
 chlorite of soda, which forms the effective constituent of 
 the bleaching liquid. Besides this principal process several 
 side-reactions take place which lessen the practical effect 
 and mainly consist in the formation of chlorate and the re- 
 duction of already formed sub-chlorite of soda to chloride 
 of sodium. These side-reactions formed one of the princi- 
 pal difficulties in working out the electric bleach method. 
 Then also contact difficulties and disagreeable experiences 
 with the different electrodes came up. Carbon electrodes 
 :are certainly cheap, but are quickly consumed and require 
 filtration of the bleach liquid. Whereas platinum elec- 
 trodes, if anyway durable, are very expensive and on ac- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 149 
 
 count of the high amortisation add much to the manufac- 
 turing expenses. 
 
 By introduction of his pointed electrodes Dr. Karl 
 Kellner believes he has found a practical solution of the 
 question. These electrodes are plates of hard rubber, or 
 other 4 resistant material, which in the form of a. brush are 
 provided with platinum points and in a box of ebonite are 
 connected for tension. With this arrangement, it is claim- 
 ed, to produce under very favorable circumstances solu- 
 tions with to 1$ active chlorine, which concentration is 
 
 =ffb 
 
 5»?^0!ro^ 
 
 gc a gga s TOsyfys^iggCT y -,.v?*'» r 
 
 Fig. 66. 
 
 for most requirements perfectly sufficient. The com- 
 position of the produced 1$ bleach liquid is with equal 
 conditions of current mainly depending on the concentra- 
 tion of the salt solution employed and on the temperature 
 observed in the electrolysis. 
 
 The bleach liquid, of 1$ active chlorine, produced under 
 normal conditions from 10$ salt solution, contains: 
 
 2.09$ hypochlorite of soda 
 
 0.60$ chlorate of soda 
 
 7.90$ undecomposed chloride of soda 
 
 The 6$ chlorine contained in a 10$ salt solution conse- 
 quently divide as follows: 
 
150 THE MANUFACTURE OP CELLULOSE. 
 
 1.00 CI as Na CI 
 
 0.2^ CI as Na CI 03 
 
 4,70 CI as Na CI. 
 
 The bleach liquid running off is entirely clear and open 
 and keeps unchanged quite long. After standing for days 
 the bleaching strength decreases, as with solutions of chlor- 
 ide of lime; the decreasing is different, according to wheth- 
 er the liquid is kept in the dark or in the light. 
 V. WASHING, BLEACHING, FINISHING OF THE 
 CELLULOSE. 
 
 These finishing manipulations, although different in 
 character, are not connected with the kind of methods here- 
 tofore treated, and may therefore be treated now, without 
 regard to them. When the knots were not bored out, or 
 sorted out before boiling the wood then after the discharg- 
 ing of the digesters, sorting by boys and girls must be done, 
 especially when the wood had been cut into slices. In this 
 case the workmen throw the cellulose on a table, divide 
 the soft mass with the fingers and in this manner easily 
 find the knots and hard pieces of wood, which have, per- 
 haps, been only partially boiled. When yellowish and hard- 
 er cellulose adhere to the knots, they are laid aside and 
 worked up later on, to obtain an inferior cellulose, so-called 
 third quality. As, however, in spite of all sorting the 
 knots do not absolutely disappear and a forcible dividing 
 would disintegrate the fibres adjacent to the knots, by 
 which the quality of the cellulose would be lessened, it is 
 necessary to take care that this separating of the fibres is 
 done as carefully as possible. Mitscherlich has employed 
 for this purpose a stamping mill, which however does not 
 properly crush the stuff, but rather grinds it, as shown in 
 the following discription. 
 
 Fig. 67 represents a sideview and section of such stamp- 
 ing mill. In about seven iron frames A rests the thumb- 
 shaft B, rotating about ten times per minute. The frames 
 are connected by two pairs of heavy timber, Cl C2, and 
 Dl D2, which at the same time serve as guides for about 60 
 stampers, one next to the other, which again reach to near 
 the bottom of the stamping-trough E, sketched ^n section, 
 which is about 15 meters long, and inclining abort 0.6 
 meter, counting from the head to the end. The lifting 
 thumbs are set around the shaft in such manner that three 
 
THE MANUFACTURE OF CELLULOSE. 
 
 151 
 
 or four neighboring- stampers are not lifted at the same 
 time with every revolution, but one after the other; so that 
 they work as shown in fig. 08, representing part of the fronl 
 view. In this manner, the first stamper, at the head of 
 
 Fig. 67. 
 the trough, when going down, carries part of the stuff to 
 the second, this one to the third, and so on; until finally, 
 while water is continuously running in, the stuff reaches 
 the other end of the trough in the form of a thin pulp. 
 As the stampers do not quite reach the bottom and carry 
 
152 THE MANUFACTURE OF CELLULOSE. 
 
 below a wider shoe., but do not touch at the sides when the 
 one stamper falls and the next one is lifted, the stuff is 
 slightly triturated in the spaces between without injur- 
 ing the fibre or crushing the hard pieces and knots. The 
 picked cellulose is poured in the lower end of the stamping 
 trough by the workmen, or, when the sorting takes place 
 in an upper loft, in a large, wooden funnel, by which the 
 stuff is continuously fed to the trough. A workman then 
 has to regulate this feeding, also the water supply and at 
 times he must assist the stuff to move along the trough. By 
 more or less closing the outlet opening of the trough, the 
 stuff is retained in the trough for a longer time and more 
 or less worked through, as made necessary by the quality 
 obtained in the boiling operation. A second necessary labor 
 is the washing of the stuff, that every trace of leach, es- 
 pecially of sulphurous acid is removed from the cellulose. 
 This, according to Mitscherlich, is not done in a violent 
 manner, but by a system of so-called wash troughs, by 
 which though much water is used the fibering and wash- 
 ing is done very effectively, and at the same time an assort- 
 ing is effected, so that at the end only the finest fibres flow 
 off, while all heavier particles settle before. As it is es- 
 sential, to make the trough as long as possible, in order to 
 save space two such troughs are generally arranged one 
 above the other. They are given the form shown in 
 fig. 69. 
 
 A wooden trough about 1 meter wide and 300 milli- 
 meters deep is provided at the bottom with so-called sacks 
 or knot-catchers, in which all knots, hard wood particles 
 and coarse splinters, kept back, settle; which later on, when 
 cleansing of the troughs becomes necessary, are let off by 
 holes provided with bungs. As soon as the stuff leaves the 
 stamping trough, it is next by one or more powerful sprays 
 of cold water, not only diluted, but the loosely connecting 
 bundles of fibres are at the same time washed apart, so that 
 the much diluted mass consists mainly of separate cellu- 
 lose fibres, floating side by side. For more effective separa- 
 tion the stuff is often at the head of the trough made to 
 pass one or several stirrers, or a so-called knot beater is 
 used, as employed in paper mills, which have centrifugal 
 hollanders; or the stuff is first let over a plain, large knot 
 catch, formed of wooden slats, provided with a shaking 
 
THE MANUFACTURE OF CELLULOSE. 
 
 153 
 
 Fig. 69. 
 
154 THE MANUFACTURE OF CELLULOSE. 
 
 arrangement. By these arrangements the lime, gyps and 
 coarser fibres are retained, but the small splinters, which 
 indeed are really but small bundles of fibres, not yet 
 separated, but otherwise soft particles of cellulose, stay in 
 the stuff, and must be removed, as much as possible. This 
 is done by either one or two, or a whole system of plate- 
 knot-catchers. The whole stuff must go through the nar- 
 row slits of the knot-catcher plates, which is affected by 
 beating with an up and down motion, which causes the 
 stuff to be sucked through. A convenient arrangement of 
 this kind is shown in figs. 70 and 71. 
 
 By an elevator or by a worm the stuff is lifted from the 
 stamping trough and enters the wash-trough at A. It 
 flows, much diluted with water, through the different sec- 
 tions, as indicated by the arrows, and finally enters a small 
 trough B, from which it runs on the four plate-knot-catch- 
 ers, arranged side by side, under it in the trough C and 
 from there it is carried to the fillers. 
 
 Lately, however, the Wandel cellulose cleaners are used. 
 They are quite similar to the rotating knot-catchers pre- 
 viously built by the same firm. The only practical al- 
 teration is that they are not moved up and down by pad- 
 dle wheels, but are rotated very quickly and thus suck in- 
 side the thin stuff, by which they are almost totally sur- 
 rounded, and consequently they work perfectly noiselessly. 
 
 Lately Wandel has constructed another sorting arrange- 
 ment for cell-stuff and patented it in America under No. 
 478,170. In the Papier Zeitung the description reads as 
 follows: The stuff to be sorted flows through a trough a as 
 into a tank al, in which is set a quickly rotating sorting 
 cylinder b, as its circumference provided with fine slits. • 
 The fine stuff enters through the slits into the cylinder and 
 runs off through the central openings at both ends. Inside 
 the cylinder are fastened the paddles d, forming with the 
 circumference an angle of about 45° and with the rotating 
 of the cylinder in the direction of the arrow act with suc- 
 tion on the stuff, and acclerate its passing. The coarse stuff 
 settles on the round bottom of the trough and is removed 
 through the channel h at the side, the cover of which, i, is 
 for this purpose opened without interrupting the work. For 
 totally discharging and cleaning the trough a, the opening 
 k is provided. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 155 
 
 A centrifugal cell-stuff sorter is built by Wagner & Co. 
 and described in the Papier Zeitung as follows: 
 
 The cell-stuff, mixed with much water, is conducted 
 
 ~T ~ B i — i 1 
 
 ■zzza rirnnn milium, iifiritii)iin i ri,in , i l. 
 
 1 — ? % B 
 
 Fig. 71. 
 
 through the pipe d to the lower narrow part of the trough 
 c, filling this up to the overrun e, from where it flows 
 over a wide trough, not shown here. To get there, the 
 
156 THE MANUFACTURE OF CELLULOSE. 
 
 stuff must pass the sieve-cap, consisting of the knot-catch- 
 er-plates a. These 3 mm. strong brass plates are provided 
 with straight slits of 4-10, 5-10 or 6-10 mm width. The 
 frame, in which the plates are set, consists of the foot piece 
 a3 (fig. 73) of hardwood, into which are let the vertical 
 plates, also the joints al and the stiffening bows of iron, 
 copper or bronze of 60 mm. width and 12 to 15 mm. 
 height, which connect all cross-pieces, and serve as im- 
 post for the one meter long plates. There will consequent- 
 ly be one such bow for each meter length. At the two 
 end-bows are fastened the bows a4, by which the whole 
 sieve-cap can be lifted out, after loosening the set screws, 
 by which the foot-pieces a3 are connected to the walls g. 
 To take them out is necessary as often as the plates have 
 to be thoroughly cleaned, and can be made more convenient 
 by suspending the cap by rope and pulley. The vertical 
 plates are kept clean during working by the sprinklers c, 
 of which there are two on each side and which are regulated 
 by a cock on each end. To make the sieve cap tight at 
 both heads, the two headwalls i are cut out in triangular 
 shape and set on similarly formed inside walls h of the 
 tank, as shown by the dotted lines in fig. 73. Where the 
 edges join, they are lined with strips of felt and the weight 
 of the sieve cap by itself secures tightness. A beater bl 
 which makes 100 to 120 revolutions per minute, with its 
 wooden scoops, going through and resting on four crosses, 
 drives the stuff through the plates. The stuffing boxes b,. 
 of the beater shaft are not fastened to the wooden tank, but 
 rest on the iron support k, being thus independent of the 
 changes in the wood. A box support b2 carries the end of 
 the shaft, besides the driving pulley. The heavy impuri- 
 ties settle in the lower part of the tank and can be re- 
 moved through the slide f . The stuff should run down from 
 a height of 300 mm. above its level at e, where it runs off 
 about 50 to 80 mm. above the upper plate a. The sprinkle 
 pipes c are mainly for the purpose of keeping the stuff 
 in motion and do not need to work all the time. The up- 
 per plates have by experience proved to keep clean them- 
 selves. It is claimed that it costs little to work the sorter,, 
 as the cleaning is going on rapidly and the consumption of 
 power is small. Through a sorter of 2,500 mm. length 
 and 4-10 mm. slits 4,000 kgr. of long fibred Mitscherlich 
 stuff will go in 24 hours. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 /a; 
 
 157 
 
358 THE MANUFACTURE OF CELLULOSE. 
 
 The stuff, freed from splinters as much, as possible by 
 one or more cellulose cleaners is then run on a filtering ar- 
 rangement, like a small paper machine, only the sieve is 
 shorter, made of stronger wire, meshed wider and does 
 net have a shaking motion. After the so-called gonch- 
 
 press, as a rule the pasteboard like stuff is passed through 
 a second press, screw or lever-press, in order to obtain a 
 product as free from water as possible. The quantity of 
 water in cellulose passed through a second press and then 
 
THE MANUFACTURE OF CELLULOSE. 
 
 159 
 
 wound up in rolls as a rule amounts to about 50 p. c, 
 sometimes more. 
 
 Mitscherlich has not himself used the above described 
 filtering' arrangement, but the so-called hair cylinder, 
 which turns out the cellulose in the form of lumps. The 
 
 9 
 
 cfq' 
 
 < 
 
 
 accompanying illustrations show the same in section and 
 plane: The cylinder h, covered with a sieve o f horse-hair, is 
 conical. 
 
 The stuff enters in the direction of the arrow, the water 
 is thrown out by rapid rotation and the pasty stuff falls 
 through the opening a on a felt f, which is carried and 
 
160 THE MANUFACTURE OF CELLULOSE. 
 
 stretched by several rollers d, d, d,; passes between the 
 press rollers p p and is carried away in the direction of the 
 arrow. After this water is pressed out from the stuff by 
 the press rollers,, the stuff b adhering to the upper roll p 
 is scraped off by the shaver m, falling on a table and by a 
 hole in it is directly filled into a bag, S, to be shipped as so- 
 called lump cellulose. 
 
 In late years various apparatuses have come into use for 
 dividing the boiled wood, in place of the stampers, not 
 only in the Mitscherlich factories, but also in other sys- 
 tems, among which the so-called "separator^' has gained 
 the widest distribution. This does not at all injure the 
 stuff, and with comparatively small power does good work. 
 It is described as follows: 
 
 Fig. 77 and 78 show it in long and cross section. It 
 consists of two wooden drums somewhat conical, about 5 
 meters long and 1 in diameter, of which a is the upper in 
 which the stuff carried by an elevator enters at e. The 
 drums themselves are fixed, but inside of them are mov- 
 ing strong wooden shafts c d, on which are set along a 
 spiral line a large number of long sticks, which nearly 
 reach the circumference of the drum. The velocity of the 
 upper shaft c is 80-100 revolutions per minute, while the 
 lower makes about 160 revolutions. The thick stuff, 
 which in the upper drum is diluted with but little water 
 by cock w, is then, by the sticks, repeatedly driven against 
 the circumference, until leaving at the other end at f, it 
 falls into the second drum, is there diluted with more wa- 
 ter and leaves at g, with fibers entirely clear, and with still 
 more water it reaches a wash trough, as long as possible, 
 in which sand and small knotty particles can settle. At 
 the end of this wide trough one or more wash drums are 
 arranged, which remove the surplus water and from where 
 the pulp runs either directly into the bleaching-hollander 
 or is let into draining boxes. 
 
 Another new system for dividing cell stuff is Engelmay- 
 er f s system consisting of three patented apparatuses, built 
 by the C. D. Bracker Sons. The following is said about it: 
 
 After the wood is well boiled, i. e. dissolved, it is by 
 means of an elevator conducted to the first apparatus of 
 the dividing system, the fiberer, the task of which is to 
 separate the fibres from the boiled knots and the still 
 hard particles of wood. In the mixer, connected to this, 
 
THE MANUFACTURE OF CELLULOSE. 
 -O . . D , 
 
 161 
 
 
162 THE MANUFACTURE OF CELLULOSE. 
 
 the mixing and diluting is done. The knots and particles 
 left hard are separated in the sorting apparatus. From 
 there the stuff is conducted through a convenient sand- 
 pang, in which are retained the still present heavy par- 
 ticles, as well as the resins, beaten off by an apparatus, ar- 
 ranged in it. The succeeding apparatus, the washdrum 
 and filtering machines, serve to partially separate the wa- 
 ter, and the stuff then reaches the "squasher" in which 
 the straightening and dividing of the fibre is effected. The 
 conclusion of the dividing system is formed by a "dis- 
 solves" from which the stuff is conducted to the beating 
 engine and eventually to the long sieve machine. Knot- 
 and-splinter fangs are not employed. 
 
 In the following the different operations and apparatus 
 are exactly described: 
 
 1. Method for dividing the cell-stuff bundles and 
 drawing out of the fibre: The present invention forms 
 a method, to divide cell-stuff, especially sulphite cellulose, 
 thoroughly with preservation of the long fibre. This 
 could not be achieved heretofore, because the dividing of 
 the boiled cell-stuff by mills and refiners was imperfect 
 to such a degree that the stuff always contained indis- 
 solved, connecting fiber bundles, so-called splinters, which 
 had to be removed by special splinter- f angers. By the 
 present dividing method, a stuff entirely free of splinters 
 is claimed to be obtained, so that the splinter-fangers can 
 be dispensed with. 
 
 The loosening of the cell-stuff is done in such manner 
 that the boiled cellulose, after it has passed a draining 
 apparatus, goes through two rollers, which revolve with 
 different velocity and of which practically the slower re- 
 volving roller has a larger diameter. 
 
 The rollers are so finely adjusted that only the thicker par- 
 ticles, not quite boiled soft, are affected. These consist 
 of connecting fibre-bundles and exist in the finished cel- 
 lulose under the name of splinters, and they are crushed, 
 and in consequence of the unequal velocity of the circum- 
 ferences ground and dissolved into separate fibres. The 
 single fibres, already produced in boiling, are, because the 
 rollers are adjusted only for the thick fibre bundles, scarce- 
 ly touched and cannot, therefore, in passing the rollers be 
 torn by them. They thus retain their original length. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 163 
 
 Fie. 80 
 
164 THE MANUFACTURE OF CELLULOSE. 
 
 In case the cellulose should, after passing the rollers, 
 still show small splinters, it is made to go through a sec- 
 ond or through several such differential roller pairs. 
 
 In working the method the arrangement, represented 
 in the illustrations Fig. 79 side view and Fig. 80 plain is 
 used. 
 
 After the boiled cellulose has passed a sandpang d and 
 a wash-drum f, it goes to a draining arrangement of any 
 kind, which in the present case consists of an endless wire 
 sieve a, and two press-rollers b and c, between which goes 
 through the sieve a with the cellulose laying upon in thin 
 layer. The press-rollers remove all water from the cellu- 
 lose, whereby it becomes so compact that it leaves the rol- 
 lers in the shape of leaves or sheets and in this condition 
 it enters at once between the rollers A and B, rotating 
 with unequal velocity of their circumferences, where the 
 splinters or fibre-bundles are separated. 
 
 The roller B is set fixed, while the slower rotating rol- 
 ler A is set in a fork E, which turns in the boxes F. The 
 fork E is adjustable, in front by a set screw D and in back 
 by set screws C. By means of these screws, D and C, the 
 roller A is so adjusted to roller B that only the splinters 
 and fibre-bundles are caught by the rollers, whereas the 
 single fibres pass free between. The rollers are driven by 
 a pulley, set on the shaft of the quicker rotating roller B. 
 The roller A is driven by the roller B by means of the gear- 
 ing G- and H. 
 
 For greater safety the cellulose is run through a sec- 
 ond similar pair of rollers Al and Bl. By the crushing of 
 the splinters between the rollers AB and Al Bl, the leaf- 
 like continuancy of the cellulose is not injured. 3j em- 
 ploying these differential-roller pairs, a stuff is obtained 
 uniformly fine and pure. 
 
 2. Sieve drum for assorting the knots and coarser 
 parts from dissolved cell-stuff: 
 
 The present invention forms a sieve-drum for assorting 
 the knots and larger particles from dissolved cell-stuff. It 
 is characterized by a simultaneous shogging movement be- 
 sides the revolving. To this purpose the sieve-drum with 
 one end set in a traverse, is by lever and pallet wheels made 
 to have a short, shogging up and down motion, while the 
 drum is turning. In the following illustration, Fig. 81-83, 
 
THE MANUFACTURE OF CELLULOSE. 
 
 165 
 
 are represented two connected sieve-drums in front and 
 side view and in plane. 
 
 In a box-like frame B, open on top rest the two sieve- 
 drums A, the mantles of which are perforated; each sieve- 
 drum (fig. 81, left) is closed by a headwall b, possessing 
 a large central opening c, lined oy a ring d, extending out- 
 ward, and at the same time forming the front resting pin 
 for the drum. The hack end of each drum is open!" The 
 
 Fi*»-8L 
 
 271 
 
 Fig. 82. 
 
 back resting for the drum is formed by its driving shaft f, 
 fastened in the usual manner in the naves of the heads 
 of the drum, and at g (fig. 83) it rest on the frame. The 
 shaft F receives its revolution by means of the beveled 
 wheels h hi from the spindle i, which is rested squarely 
 in front of the hack end of the drum A in corresponding 
 boxes of the frame and carries the pallet-wheels k and the 
 driving pully. The pallet wheels work against the ends of 
 
166 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 the levers m, somewhat extending above, which at both 
 sides of the frame B are set revolving about the pins ml 
 and at its other ends carry the traverse n, laying square in 
 front of the other end of the sieve drum, in which are rest- 
 
 Pie. 83. 
 
 Fig. 84. 
 
 ed and revolve the extending rings d of the front drum 
 walls b. Two springs 0, which are braced against the 
 traverse n and also against the intensions p of the frame, 
 tend to lift the traverse with the front ends of the drums. 
 
THE MANUFACTURE OF CELLULOSE. 167 
 
 By the rotation of the shaft i the drums a are caused to 
 revolve and at the same time, by the pallet wheels k, the 
 
 Fig 86. 
 levers m and the springs 0. the traverses n and the front 
 ends of the drum are caused to make short, snogging up 
 
168 THE MANUFACTURE OF CELLULOSE. 
 
 and down motions. The dissolved cell-stuff flows through 
 the opening c into the sieve-drums and through the holes 
 in the mantel of the drum into the lower open space of the 
 frame B, from where it is taken away through the opening 
 r (fig.87). The knots and coarser particles fall out at the 
 open back end of the sieve-drums. 
 
 3. ARRANGEMENT FOR DERESINATING THE 
 CELL-STUFF. 
 
 The arrangement consists in the main of a beater shaft, 
 which beats the cell-stuff separating the particles of resin 
 from the cell-stuff fibres, until a lather is formed, which 
 after the liquid has come to rest, leaves upon it a fine film, 
 containing the particles of resin. There are also of one or 
 more rotating rollers, immersed in the liquid, and remov- 
 ing the particles of resin, the latter adhering to the mantel 
 face of the rollers and removed by scrapers. The rollers 
 may be cooled or warmed, as desired. In the following il- 
 lustrations fig. 84 represents a long section, fig. 85 the 
 plane and Fig. 86 the sectional cut through the roller b. 
 
 In the trough A, conducting the cell-stuff mass to the 
 sandfang, is arranged a beating spindle a, covered with a 
 ca]3 d. The cell-stuff flows from the supplying trough over 
 the wier e to the beater a, which so beats the cell-stuff, that 
 a foam is formed, in which the particles of resin accumu- 
 late. Behind the beater the cell-stuff flows over the cross- 
 wall f, behind which the form disappears and leaves a fine 
 resinous film swimming on top of the cell-stuff, which by 
 a roller b, immersed in the liquid and slowly revolving, op- 
 posite to the direction of the current, is taken up, the par- 
 ticles Ox resin forming the film adhering to the lower facr 
 of the roller. The resin is then removed above the liquid 
 by a scraper s, trailing on the roller. The scraper s rests 
 on the pin si and at its back end it is provided with a gut- 
 ter s2 to receive the resin. It receives, besides, by a lever h 
 and a curved groove K, an oscillating motion, whereby the 
 scraping off of the resin is facilitated. The curved groove 
 K is worked into the wave of worm-wheel g, sitting on the 
 spindle of the roller b and receiving its rotation from a 
 worm gl. The roller b is arranged almost over the first 
 cross-piece i of the sandfang. If desirable, several such 
 rollers C can be arranged one after the other. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 169 
 
 Ficr SS. 
 
170 THE MANUFACTURE OF CELLULOSE. 
 
 A machine for the same purpose is the Twirler of Carl 
 Ziegelmeyer, described in the Papier Zeitung, 1895, and 
 represented in Figs. 87 and 88. 
 
 It consists of a cylindrical mantle, to which are screwed 
 fast a number of beating pins f, four each in one plane, be- 
 tween which move the beating pins i, wedged in the ver- 
 tical shaft g. The number of the beating pins may be in- 
 creased or lessened as desired. The shaft is set in a step 
 box h and carries the fly wheel n, the two stuffing-boxes d2 
 and e2 are parts of the cover, closing the cylinder. The 
 driving is effected by loose and fixed pulley m and beveled 
 wheel jk. The two supports a of the strong frame are con- 
 nected by a plate b, carrying the before-mentioned foot box 
 h. The diluted stuff, mixed up with water, is by a pump 
 jnessed through pipe dl into the lower part d of the cylin- 
 der, on its way upwards being divided by the beating pins, 
 and flows from the upper part e off through the pipe el. By 
 the above described arrangement of the beating pins a twirl- 
 ing motion is produced in the inner space r of the cylinder, 
 dividing the fibres, but leaving the hard particles unchanged. 
 Because the cylinder is closed and over-pressure exists in 
 it, the stuff while going through is protected from soiling 
 and also from lubricating oil. A twirler, the cylinder of 
 which has a height of 1.2 m. and a diameter of 0.4 m., suf- 
 fices to dissolve about 5,000 kg. cell-stuff, boiled dry, in 24 
 hours, and requires but 1.5 square meters of ground. The 
 consumption of power is 2 to 3 horse-power. The twirler 
 has proved successful for eight years, in soda, as well as in 
 sulphite stuff factories. 
 
 The firm of Geetjes & Schulze, in Bautzen, builds for. 
 dissolving and fibering cell-stuff the patented machine il- 
 lustrated in the following five figures: 
 
 For this machine, after soaking and grinding the stuff, 
 the removing of the latter, as well as of the insufficiently 
 boiled particles and other impurities and admixtures is 
 effected in a specially arranged sievedrum, whereafter the 
 stuff is ground fine in one or several centrifugal mills. By 
 grinding fine is here to be understood the complete divid- 
 ing of the fibrebundles, not the crushing of the fibre. 
 
 Fig. 89 is a sideview with partial section; fig. 90 is the 
 head view of the machine. The fig. 91, 92 and 93 repre- 
 sent details. The stuff as discharged from the digester is 
 fed to the machine at a. It reaches the drum A, in which 
 
THE MANUFACTURE OF CELLULOSE. 
 
 171 
 
 is turning a shaft al with beating pine a2 (fig. 91); the drum 
 A, made of bronze or other acid resisting material, widens 
 a little from the inlet towards the outlet. By the beating 
 and throwing action of the pins a2, the fibrebundles are 
 softened and loosened. By partion walls a3, set against 
 each other, partially baring the cross space, the stuff can 
 
 Fig. 93 
 
 Fig. 89. 
 lie directed along a zig-zag way through the drum, where- 
 by the rim of the stuff is retarded and the working by 
 the shaft a becomes more effective. 
 
 After the stuff has left the drum A at b, it is in a pasty 
 •condition carried to the centre of the centrifugal mill B. 
 
172 THE MANUFACTURE OF CELLULOSE. 
 
 In this (fig. 92), which is of the usual arrangement, oppo- 
 site the fixed head bl is set on shaft b2; the rotating head 
 b3, both heads are set with beating pins of square cut. The 
 object of this centrifugal mill is the previous grinding of 
 the stuff, as against the grinding fine, to be described later 
 on. It is the purpose to continue the softening and 
 
 Figs. 90, 91, 92. 
 
 loosening, commenced in A, until the dividing of the fibre- 
 bundles, but most of all to bring the stuff in a condition 
 in which the knots and other impurities or admixtures are 
 separated from the cellstuff, without being ground. 
 
 This separating of the knots, etc., is effected in a sieve- 
 
THE MANUFACTURE OF CELLULOSE. 173 
 
 drum, C. into which the stuff enters through the bent pipe 
 e, starting at the circumference of B. 
 
 The hollow neck cl, at the left side of the drum, carries 
 a disk c2, with which the left end of the drum is resting 
 o i the friction and guide-rollers, c3, of which one is 
 wedged on thr driving pin cl. In similar manner the right 
 end of the drum with a disk c5 of wedge-like shape is rest- 
 ing on grooved rollers c6. As perceivable from fig. 90 the 
 axis of the drum has an oblique position, being lowered 
 towards the entrance end of the left side. So far as the 
 exit end the sieve mantel is immersed in a trough cl, filled 
 with water and stuff. The bent pipe c is covered inside 
 the drum by a cap c7 in such manner that the stuff cannot 
 be thrown through the drum along the direction of the 
 axis, but must leave c in a radial direction. The mantle 
 of the drum is fitted inside with a winding alley c8 (fig 
 93); by a pipe c9. Water can be injected when necessary. 
 
 Whilst the stuff conducted to the sieve drum through 
 pipe c is slowly moved on by c8, the sufficiently divided 
 particles pass through the sieve mantle into the water, 
 while the knots and such other matter are carried along 
 by the spiral c8. The position of the axis of the drum to 
 the level of the water causes the knots to keep swimming 
 and not to be in the way of the passage of the stuff parti- 
 cles towards Cl; until, nearing the end of the drum, they 
 reach the mantle and are by the spiral carried to the shoot 
 C3. In Cl besides the pure stuff are now also contained 
 the heavy impurities, which pass the sieve mantle; these 
 sink to the bottom, while the stuff flows over 02 through 
 the bent pipe d into the centre mill D for grinding fine, i. 
 e., for thorough separation of the fibres. Through the 
 pipe dl water can be supplied to this centrifugal mill, 
 should it become necessary. Its inner arrangement corre- 
 sponds to that of the already described centrifugal mill B. 
 
 Also based on the principle of centrifuging, Hagemann 
 & Co. have built a patented wet, centrifuge with circulat- 
 ing vessel for milling cellstuff after digesting. This cen- 
 trifuge is arranged over a cylindrical pipe g, the upper 
 edge of which is formed into a ring-like closed box c, the 
 cover of which also answers the fixed peg-ring of th( 
 centrifuge. The shaft 1, which carries the upper, rotating 
 peg-disk f and the axis of which falls together with that 
 of the pipe g, goes through the bottom of the circulating 
 
174 THE MANUFACTURE OF CELLULOSE. 
 
 vessel and is consequently intended to be driven from be- 
 low. The pegs d of the fixed ring are provided with axial 
 bore almost up to the point, communicating with the ring 
 box c. This is connected with a water supply through a 
 pipe b, from which the water enters the bores of the pegs 
 under pressure. From these the water is forced through 
 small holes, divided along the pegs and against the pegs e 
 of the revolving disk f. To prevent the water from get- 
 ting outside along the face of the disk f, it is of advantage 
 to cut grooves in the rotating disk f, over the peg-ring of 
 the fixed disk, i. e., over the water outlets, in order that the 
 water may be turned off downwards and led between the 
 pegs. These, with sufficient velocity of rotation, atomize 
 the water and throw it out with great force tangentially; 
 whereby it acts with suction similarly to the well known 
 ejectors. The stuff standing in pipe g but little below its 
 upper edge, is therefore sucked up, fed to the centrifuge 
 and by it filtered and mixed. The stuff now thrown out 
 by the centrifuge, with great force, is with advantage 
 thrown against a concentric wall, whereby it suffers fur- 
 ther division. From this wall the stuff f then flows either 
 directly or through a trough or channel into a suitable 
 vessel, which communicates with the lower end of the pipe 
 g. In this manner a circulation is obtained which makes 
 it possible to run the stuff through the centrifuge as often 
 as desired. 
 
 When the stuff at the same time is to be washed, as is 
 always desired in the milling of cellstuff, it is practical to 
 give the circulating vessel the form of the hollander tank, 
 in which there are then arranged the washdrums in the 
 customary manner. When washing the water can be con- 
 tinuously supplied through the lower pegs of the centri- 
 fuge, whereas when only fibring or mixing of the stuff is in 
 question, the water is but supplied to the pegs only until 
 the stuff is sucked up, when the water supply is then shut 
 off. 
 
 The described centrifuge is arranged in the middle of a 
 double hollander tank U IT. The hollander box and the 
 frame of the centrifuge are made of cement and only the 
 working parts and valves, etc., have to be made of metal. 
 
 When the circulating vessel U is sufficiently filled -with 
 stuff, the shutter a is opened. The water now enters from 
 the pipe line b into the ring-like box c, and from there in 
 
THE MANUFACTURE OF CELLULOSE. 
 
 175 
 
176 
 
 THE MANUFACTURE OF CELLULOSE. 
 
 to the pegs d. From these the water spouts through the 
 already mentioned small holes against the pegs e of the ro 
 fating disk f, which atomize and throw it out; the stuff 
 thereby sucked up rises in pipe g, passes the centrifuge and 
 is thrown against the walls of the ring-channel h. From 
 this channel^ on which are formed four saddles i for the 
 equal distribution of the stuff, the latter flows through the 
 four openings k into the outer compartments of the three- 
 parted hollander tank. The arrows mark the further cir- 
 culation of the stuff until it reaches again the centrifuge. 
 A simple arrangement for the separating of the cellstufl 
 from the waste leach has been patented by George Seiler 
 and Franklin Emig, of Spring Forge, Penn. (American 
 patent No. 514,780.) It is described as follows: 
 
 Fiff. 96. 
 
 To separate the cellstuff from the waste leach as com- 
 pletely as possible without employing wash water, the cell- 
 stuff coming from the digester, saturated with leach, is 
 run into the funnel B, from where, after opening a slide, 
 it falls on an endless, penetratable ribbon c, (for example 
 a sieve,) which carries it through one or more pairs of press 
 rollers D D and then, in dry condition, into the space Gr. 
 In this space it is so much diluted by water, supplied by 
 the channel e, that it can be pumped to any place desired 
 for further working. The waste leach accommulates in 
 the compartment F without becoming diluted at all. 
 
 For milling the boiled cellulose, Karl Kellner had pat- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 177 
 
 ented under Am. pat. No. 489,079, the following described 
 machine: 
 
 By this invention the knots, undissolved in boiling, are 
 prevented from becoming disintegrated and getting into 
 the paper. The case of the machine, as seen in Fig. 98, is 
 
 Fig. 98. 
 almost elliptical in cross section and conical in such man- 
 ner that from the end where the cellstuff is introduced (g) 
 it becomes wider towards the other end. The dividing of 
 the cellstuff is effected by beaters d and dl, which are fast- 
 
ITS 
 
 THE MANUFACTURE OP CELLULOSE. 
 
 ened to the naves wedged to the shafts c and cl and with 
 these naves form one piece each. The beaters of the one 
 shaft move between the beaters upon the other shaft, with- 
 out touching them, so that the knots are left uncrushed. 
 Corresponding to the conical form of the case, the beaters 
 become longer from one end to the other. To facilitate the 
 discharging a pipe h is arranged opposite the exit pipe k, 
 through which the water is supplied. The cellstuff is in- 
 troduced in the condition of a thick, half-dry dough. The 
 two shafts, c and cl, are driven in opposite directions by 
 means of pulleys f and fl. 
 
 Another arrangement for the milling of boiled wood and 
 the separating of knots from the stuff is that of Phillip 
 Dietz. 
 
 Fig. 99. 
 
 The arrangement consists mainly of the conical drum 
 T, inclined on one side. It has, where its diameter is 
 smallest, the inlet opening P for the boiled wood ;at the 
 other end, where the diameter is the largest, the outlet E 
 for the pasty stuff and also an opening for cleaning K are 
 arranged. The narrow part of the drum is lined with a 
 pad or cover H, of rubber, felt or other material. In the 
 wider part of the drum are arranged three copper water 
 supply pipes z. 
 
 To the shaft W of the drum are fitted the spokes N, along 
 a spiral line; the latter, together with the shaft, are cov- 
 ered with a pad of rubber in such manner that between 
 the lining of the drum and the ends of the spokes a free 
 
THE MANUFACTURE OP CELLULOSE. 179 
 
 space is left. At the outlet E stops are fixed adjustable 
 to make a stopping of the stuff possible. Further, for fur- 
 ther division, a pro-sorting box S is arranged with the 
 sprinkle pipes Q and the outlet openings L. 
 
 The boiled wood, which is conducted from the digesters 
 or storage room to the inlet P, is worked dry in that part 
 of the drum in which is the padding H. By the latter as 
 well as by the padding of the shaft and spokes is prevent- 
 ed the crushing of the hard particles of wood and of the 
 knots. 
 
 The spokes N push the stuff ahead in such manner that 
 each of them works the stuff ahead to the next one. In 
 order to be able to change the number of revolutions of 
 the spokewheel quickly, step-pulleys are employed. While 
 in the upper narrow half of the drum the soft-boiled parts 
 are separated from the knots, in the lower wet part, the 
 flocks are completely fibred and disssolved. The stuff 
 passes gradually over the wier and then receives liberal 
 addition of water. In the pro-sorting box S the knots, as 
 well as unboiled particles of wood and other admixtures, 
 next settle down. After the fibres still adhering to the 
 knots are removed by the sprinklers, before they can set- 
 tle to the bottom, the stuff is finally conducted to a trough 
 or sandfang of the customary construction. 
 
 After the single rolls are wrapped in good packing, pa- 
 pered and corded, or packed otherwise, the product is 
 ready for shipping, but care must lie taken that before 
 packing sufficient samples are taken that the amount of 
 moisture, which in shipping goods in moist condition 
 form an important item, and often causes differences, can 
 be determined as closely as possible. 
 
 The working of moist cellulose is very convenient for 
 the paper manufacturer. Lately, however moist cellulose 
 factories have provided for drying cylinders and thus 
 formed the wet machine into a regular paper machine, able 
 to produce absolutely dry stuff or almost dry, of about 80 
 to 90°, and thus to save freight expense or to be able to 
 sell the cellulose in far-off markets with profit. Fortun- 
 ately the drying is not of much disadvantage to the paper 
 manufacturer, although it is claimed the fibre loses some 
 of its firmness; but it dissolves easily in water and offers the 
 advantage that it can be kept in store for any length of 
 
180 THE MANUFACTURE OF CELLULOSE. 
 
 time without danger of getting musty, as happens easily 
 with moist straw stuff. 
 
 Some factories, shipping the cellulose in moist condi- 
 tion, who have to serve their customers a specially pure 
 product, after having finished rolling are doing another 
 sorting by repeated off and up rolling, which is done with 
 a small apparatus, represented in Fig. 100 and 101: 
 
 An upright frame A carries several boxes; in the lower 
 one is set a spindle, on which is fitted the roll B of cellu- 
 lose to be assorted; above are arranged two guide rollers c 
 and d and further up a strong wooden roller E (200 mm 
 diameter) which by a belt from the transmission is slowly 
 turned (8 revolutions per minute). Over it are arranged 
 two forklike slide boxes, in which is laid the roller on 
 which the cellulose to be sorted is rolled up. After a roll 
 of cellulose is put in below, and drawn over the guide rol- 
 lers and the wooden roller E and around the roller f, the 
 winding up will start above. The cellulose breadth, as a 
 rule 1 meter wide, is slowly moved upward in the direc- 
 tion of the arrow and the roll B is gradually rolled off. At 
 both sides of the frame girls stand to pull out all impuri- 
 ties or larger splinters with their fingers, while the ma- 
 chine is going. When the girls are careful the result of 
 the sorting is good, but the expense in wages is not small, 
 several sorting frames are necessary (about three for every 
 digester) and besides the loss of stuff amounts to 15 per 
 cent, which, however, is used again along with the second 
 quality. 
 
 All those cellstuff factories, which work for export, are 
 required to perforate the dry cellstuff boards, that they 
 are not taken for real pasteboard by the revenue officials, 
 and as such taxed higher. This was formerly effected by 
 arranging a pipe under the sieve, by which periodically 
 strong jets of water were sent from below through the 
 stuff-mass. Thereby, however, strong edges were unfor- 
 tunately formed around the perforations, which in press- 
 ing caused unequal states of dryness. 
 
 Because the government now requests regular perfora- 
 tion, different apparatuses have been constructed. 
 
 One of them, built and patented by the Kuehule ma- 
 chine factory in Frankenthal, is described and illustrated 
 in the Papier Zeitung. 
 
 By this arrangement the perforating of the paste is done 
 
THE MANUFACTURE OF CELLULOSE. 181 
 
 on the wet machine in such manner that the cellstuff can- 
 not be taken for pasteboard by the revenue authorities. 
 The dies and sinkers, which are fixed to a frame swinging 
 around an axis, follow the finished sheet of dry stuff, while 
 perforating and there at once return to starting position. 
 
 1 
 
 *& 
 
 ^ 
 
 K 
 
 SI 
 
 Jl 
 
 5» 
 
 E 
 
 tp 
 
 3E 
 
 sn 
 
 FF 
 
 w 
 
 100-101. 
 
 As advantages of this arrangement are claimed: 
 First. — Faultless perforation, i. e., no injuring of the 
 good appearance of the stuff by the perforating; second, 
 
182 THE MANUFACTURE OF CELLULOSE. 
 
 preservation of the expensive transport sieves, against the 
 method of perforating by water jets and others; third, 
 convenient application of the arrangement to any machine. 
 
 A mnch more simple arrangement for perforating cell- 
 stuff board is the one of H. Fullner in Warmbrunn. An 
 upper roller is provided with pins, which fit into corre- 
 sponding holes of the lower roller and cut just as many 
 holes into the stuff board. The pins are edged on the outer 
 face, in order to make an incision and not tear through. 
 A scraper, laying against the upper roller, holds back the 
 shreds possibly adhering. It may.be conveniently taken 
 off the board of stuff if necessary and is provided with 
 notches, which permit the pins to pass. 
 
 The upper roller, with the pins of hard steel set in, is 
 of cast iron, whereas the counter roller with the holes is 
 made of steel tube so that the edges of the holes form steel- 
 cutters, working together with the steel pins. The per-, 
 f orator can be made so that all four sides of the pin cut, 
 and the pieces of cell-stuff board cut out, fall into the hol- 
 low space of the lower roller; they accumulate there, until 
 pushed to the ends, where they drop through four round 
 holes into the wooden boxes standing under. 
 
 If the square clippings of cell-stuff should stick to the 
 cell-stuff pieces, only three sides of the pins are made to 
 cut, so that on its back side the clippings are left con- 
 nected with the piece. The piece is then passed under a 
 strike-board, which turns the clippings over and by rol- 
 lers they are so pressed against the drying cylinders that 
 the turned over clipping will stick to the piece and leave 
 the holes entirely open. 
 
 The perforator is mostly connected in the paper ma- 
 chine between pressers and dryer. 
 
 Many factories sell part of their production in bleached 
 state and then up to rolling up and assorting treat the cell- 
 ulose in the same manner as described above, after which 
 an ordinary bleaching hollander is employed. This should 
 be of at least 300 kilos hold of stuff. Let it first be al- 
 most filled with water, warmed by steam and then from a 
 box standing near the hollander, and holding exactly the 
 quantity of the chlorine water necessary to be added, 
 (1-J cubic meter for above quantity of stuff) the chlorine 
 is let into the hollander. Then is introduced the stuff, 
 the damp cellulose, wound up in rolls. In about three 
 
THE MANUFACTURE OF CELLULOSE. 183 
 
 hours the bleaching process is finished and this is follow- 
 ed by washing, which requires one hour, and then the 
 bleached cellulose can be let into the stuff-tanks, from 
 where it goes to the before mentioned drainer and is wound 
 up again in rolls. 
 
 For several years there has been used for the bleaching 
 of cell-stuff a hollander which varies from the ordinary 
 form, but possesses highest efficiency, because it effects 
 closest and quickest mixing of the stuff with the bleach 
 water and with the utmost cleanliness. It is the wash- 
 bleach-hollander built and patented by Emil Nacke, which 
 is made in large dimensions: 9 m. length and 4^ m. width, 
 inside measure, and holds 1400 kgr. stuff. 
 
 The moving and mixing of the siuff is not done by pad- 
 dle wheel, but by a turbine-like wheel of 650 millimeters 
 diameter, which is arranged at the bottom, makes 200 rev- 
 olutions per minute and is driven by a belt from below, so 
 that of the driving mechanism nothing at all can be seen. 
 By this wheel the stuff is moved around noiselessly. The 
 current is so strong that the stagnation of the stuff in the 
 corners is entirely obviated and the use of stirrers is unnec- 
 essary. Except with the walls, which are lined with white 
 tiles, the stuff comes in contact with nothing but phosphor 
 bronze and glass, which substances are resistant against 
 acid and chlorine and hence clean. The wheel f, which ro- 
 tates above the bronze plate a, is of phosphor bronze and 
 the plates b and c are of glass. The stuff, moving in the 
 hollander towards the wheel, is by the inclined glass plate 
 b turned downwards, then, as the arrows show, sucKed off 
 by the wheel and after going through the wheel leaves at 
 its circumference m current: spreading in the form of a 
 fan. The stuff leading the wheel toward the front pro- 
 duces a strong undercurrent close to the bottom of the hol- 
 lander, by which all settling of stuff at the bottom and in 
 the corners is prevented. The stuff leaving towards the 
 glass plate b, is by this and the glass plate c, as the arrows 
 indicate, also turned towards the front and forms together 
 with the under current the strong draft of this hollander. 
 The difference between the levels of the stuff in front and 
 behind the plate b amounts to three-fourths meter and by 
 this in fact is conditioned the lively current of the hol- 
 lander. The mixture produced by the hollander is al- 
 
1S4 THE MANUFACTURE OF CELLULOSE. 
 
 ready a perfect one after once going through, so that the 
 chlorine water introduced at one place, after going but 
 once through the wheel, is mixed quite uniformity with 
 the stuff. In tlie same even manner the heating of the 
 stuff is done by a current of steam let in; the temperature 
 of the stuff, even in the largest hollander, is thereby in- 
 creased about the same all over; so that the temperature 
 can be made the most favorable for the bleaching process, 
 without part of the stuff becoming heated the fraction of 
 a degree above or below. 
 
 The Kack hollander has inside of the tank no hidden 
 corners and nooks, every part of it lays entirely open to 
 the eye, after the stuff is let off. This, together with the 
 clean, acid and chlorine resisting material, is an impor- 
 tant advantage, where the production of the purest stuff 
 is the question. 
 
 Because the hollander is also used for washing, ISTacke 
 also uses a washdrum, not the ordinary one, however, but 
 an aspirator wash-drum of his own system, which works 
 so easy that it does not require special power, but is driven 
 by the motion of the stuff. Gearing and belts with their 
 uncleanliness are therefore dispensed with. This wash- 
 drum furthermore also washes much more energetically 
 than the ordinary dipping washdrum and has over this 
 the other advantage that the sieve lining last twice as 
 long and the loss of fibre in washing is much less. 
 
 The arrangement is as follows: The washdrum is a 
 simple cylinder, provided with a fine sieve lining, turns 
 loosely on a hollow, fixed shaft, on which, inside of the 
 drum, are set three aspirator pipes, open below, turned 
 downward into the water. Because the shaft is fixed 
 these aspiidtor pipes maintain their downward position. 
 Outside of the hollander wall is screwed to the hollow 
 shaft a long fill tube, dipping into a box, in which is a 
 partition of adjustable height, permitting the regulation 
 of the quantity running off. The deeper the weir is set 
 the stronger the drum will suck. To complete and main- 
 tain the vacuum a small aspirator is used, it is driven by 
 water, which is supplied by a hose under four meters 
 pressure or more. The hose is 20 mm. wide, but the 
 bore in the aspirator is only 5 mm., the consumption of 
 water is consequently very small. Through a second rub- 
 ber hose the consumed water runs off into a tank. The 
 
THE MANUFACTURE OF CELLULOSE. 
 
 185 
 
 first water-supplying hose must be long enough so that 
 the drum can be entirely lifted out when no washing is to 
 be done. In the other case, the wash drum is let down 
 by a set-wheel, so that it immerses into the stuff, displaces 
 it somewhat and lets the dirt-water penetrate through the 
 sieve-lining into the interior. The rotating stuff at once 
 
 Fig. 102. 
 sets the drum into revolving motion so that it is con- 
 tinuously offering a face to the penetrating water. The 
 aspirating apparatus is set working by opening the water- 
 
186 THE MANUFACTURE OF CELLULOSE. . 
 
 supply valve, a vacuum is caused in the hollow stuff, the 
 dirt-water is raised up through the aspirating pipes, is 
 received by the hollow shaft and conducted away Toy the 
 outlet pipe attached to it, and because this is emersed in 
 the box filled with water, a continuous aspirating of the 
 dirt-water is affected. 
 
 Although the method is not yet introduced in cellulop:-- 
 factories, the electric bleaching, worked out by E. 
 Hermite could be employed in place of bleaching with 
 chloride of lime. This is claimed to yield a saving of at 
 least 50 per cent in bleaching material. With wider ex- 
 tension of the latest Kellner method of producing cell- 
 stuff by means of the electric current, this bleach would 
 certainly not be necessary because as heretofore mention- 
 ed, by this a snow-white stuff is already produced. But 
 for the sake of completeness this bleaching method 
 should be mentioned. It is based on the following: When 
 a solution of chloride of magnesia of 5 per cent, chloride 
 of magnesia and 95 per cent, water is electrolized in a 
 convenient arrangement, water and chloride of mag- 
 nesia are simultaneously decomposed. The chlorine sepa- 
 rated from the chloride of magnesia, and the oxygen, 
 from the water, under the influence of the electrolysis, 
 combine at the positive pole and produce a loose chlorine- 
 oxygen combination, which is possessed of strongly de- 
 colorizing quality. 
 
 The hydrogen and the magnesium go to the negative 
 pole. This decomposes water and forms magnesium oxide, 
 while hydrogen is set free. When vegetable fibre is 
 brought into such liquid, the oxygen combines with the 
 coloring substance and oxydizes it; the chlorine combines 
 with the hydrogen and forms hydrogen-chloride, which 
 again goes into combination with the magnesia in the 
 liquid and reproduces anew the chloride of magnesia. This 
 circulation is repeated as long as the electric current is 
 acting on the solution, holding the colored substance. To 
 a perfect circulation of this kind are therefore necessary. 
 First, electric current; second, chloride of magnesia' 
 third, water; four, coloring substances. 
 
 Two of these elements serve to destroy the coloring sub 
 stances; viz., the electric current, or, what amounts to 
 the same thing, the acting force and the water. Tbe 
 chloride of magnesia serves continuously; only a simph 
 
THE MANUFACTURE OF CELLULOSE. 187 
 
 moving of the molecules takes place and the chlorine acts 
 as a conductor, bringing the oxygen produced to the col- 
 oring substances. It has been proved that the electric 
 method exercises a. quicker decolorizing action than com- 
 mon chloride of lime. 
 
 In general Hermite points out the advantages of his 
 
 Fig. 103. 
 method as follows: First, it permits every bleacher to pro- 
 duce for himself the discoloring substances and this with- 
 out noticeable interruption of his work; second, the de- 
 colorizing means is pure and does not leave a residue; 
 
188 THE MANUFACTURE OF CELLULOSE. 
 
 third, it possesses considerably greater decolorizing effect 
 than chloride of lime; fourth, its action on fibres ensues 
 quicker, is more uniform and is less injurious; fifth, its 
 employment means considerable saving of money; sixth, 
 the cost of production is uniform. 
 
 In this method only that part of chloride of magnesia 
 is lost which is contained in the damp stuff after press- 
 ing. At 40 per cent dryness there are to be considered 
 40 kilos of stuff and 60 kilos of water; then for 100 kilos 
 of dry stuff 150 kilos of chloride of magnesium solution gets 
 lost, containing 10^ kilos of chloride of magnesia. 
 
 The apparatuses for electric bleaching are built by 
 Paterson and Cooper in London. The electrolysor con- 
 sists of a cast iron vessel, in the lower part of which is 
 let in a perforated pipe, provided with a zinc cock, 
 through this pipe the chloride of magnesium solution 
 enters the apparatus; its upper edge is flattened out, re- 
 ceives the overflowing solution, and conducts it to another 
 vertical pipe. This second serves to create the circula- 
 tion of the solution. Along the length of the electro- 
 lysor lay two shafts, to which are fixed disks of zinc; 
 these disks of zinc are the negative electrodes and move 
 in slow rotation. Intermitted with .each negative elec- 
 trode is set a positive electrode; the active surface of 
 which consists of platinum netting held in a frame of 
 hard rubber. The upper part of the platinum netting is 
 soldered to a lead body and completely isolated. By means 
 of this lead body every positive electrode is connected 
 with the copper circuit, conducted through the electroly- 
 sor; the contact is effected by a female screw. During 
 working any electrode can be taken out, without any in- 
 terupting of the process in the apparatus. In connection 
 with the copper conductor to which the positive electrodes 
 are fastened, is the positive pole of the dynamo machine. 
 The electric current now distributes itself upon all plati- 
 num electrodes, goes through the liquid in the zinc 
 disks, i. e., negative electrodes and connects by means 
 of the galvanic cast iron vessel with the negative pole of 
 the dynamo machine. For the purpose of keeping them 
 clean elastic scrapers of hard rubber are arranged at the 
 positive electrodes, tightly lying against the zinc disks. 
 These they keep clean of every deposit while slowly ro- 
 tating. The apparatus can be emptied by opening a valve. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 189 
 
 When several apparatuses are used, they are set for 
 intensity, i. e., the positive pole of the first is connected 
 with the negative pole of the second, and so on. An elec- 
 tric current of 1,000 to 1,200 ampires is generally used to 
 work the electrolysor. 
 
 Each apparatus substitutes the decolorizing action of 
 about 125 kilos of English chloride of lime of about 33 
 per cent of chlorine in 24 hours of continuous work and 
 requires about 8-J horse power. The inventor guarantees 
 for every electrolysor of 1,000 ampires current the substi- 
 tution of the bleaching power of 100 kilos chloride of 
 lime, and an expense for power of 9 horse power on the 
 pulley of the dynanip machine in 24 hours work. 
 
 dr 5 * 
 
 s 
 
 bd 
 
 4 
 
 HI 
 
 m 
 
 Fig. 104. 
 
 To represent the circulation arranged in electric bleach- 
 ing, is the shematic figure, 104: 
 
 From the vessel A the solution of chloride of magnes- 
 ium, to which some magnesia is added, enters in to the 
 electrolizer B and falls from there into the bleach holland- 
 er C where the decolorizing of the stuff tobebleached takes 
 place. The wash drum D conducts the spent solution into 
 the vessel I and the centrifugal pump J carries it back to 
 the original starting point A. By means of this steadily 
 maintained circulation the solution continuously keeps up 
 
190 THE MANUFACTURE OF CELLULOSE. 
 
 the same effectiveness. When the stuff is properly decol- 
 ored it is, together with the solution still contained in the 
 hollander, let off into the vessel E, where the after-bleach 
 takes place; when this is finished, the stuff goes over the 
 wet press G, where it is deprived of its water. The solu- 
 tion running off G- is caught in the tank H, let into the 
 main tank I, and from there, by means of the pump J, re- 
 turned to the tank F. In special cases, when for instance 
 difficultly bleachable stuffs are to be bleached, it is advisa- 
 ble to previously let the solution circulate for some time 
 between the two vessels F and J; also the apparatus B. The 
 solution becomes thus more effective and the stuff is 
 bleached quicker. It may be mentioned that during 
 bleaching an excess of free magnesia is ever required in the 
 solution of magnesia chloride to maintain the latter neu- 
 tral. It can be made at home in the following manner: In 
 a high tank, filled to one-half with strong solution of chlor- 
 ide of magnesia, sufficient milk of lime is added. The lime 
 produces a jelly-like precipitate of magnesia and leaves in 
 solution chloride of lime. When the magnesia has well 
 settled the solution of chloride of lime is drawn off by sy- 
 phon and let to waste. The magnesia is then washed two 
 or three times with clean water; it is then ready for use 
 and is added to the bleach-liquid in small quantities as re- 
 quired. For the preparing of the milk of lime another 
 tank with wash drum (the latter covered with very fine 
 metallic cloth) is required. The wash drum draws out the 
 milk of lime and leaves sand and other impurities in the 
 tank. 
 
 In a Swedish cellstuff factory, during several years' 
 bleaching according to Hermite's method, for each 100 Kgr 
 cellstuff 11 Kgr tale are decomposed and it is claimed that 
 bleaching with this method, although twice as much power 
 is required than stated by Hermite, is still much cheaper 
 than with chloride of lime. 
 
 In factories where the wood intended for boiling is cut 
 by a chip machine and where consequently the pieces after 
 the boiling, though they should partially be left hard, are 
 never large, and where besides not much value is placed on 
 the production of best quality, the work in the stampers 
 and in the wash troughs is saved by crushing the stuff dis- 
 charged from the digester directly by a large mill. From 
 there the stuff is let into a basin, diluted with water and 
 
THE MANUFACTURE OF CELLULOSE. 191 
 
 directly or by means of a pump conducted to the hollander. 
 Here it is beaten for some time, but not ground, and yet 
 receives an addition of dilute muriatic acid, whereby the 
 whiteness of the stuff is raised, afterwards going to the wet 
 machine for finishing. Because in this method the knots 
 are not all removed only a second quality stuff is naturally 
 obtained. 
 
 In order to utilize as much as possible the knots and the 
 stuff adhering to them, some factories use still another 
 mill, which works up all waste and crushes also the knots, 
 at least into small pieces. This milled stuff, which is left 
 possibly dry, is scooped into a quickly rotating sieve drum 
 of inclined position which sifts the stuff which can be made 
 use of while all larger, hard pieces come out at the lower 
 end. The stuff obtained is naturally very poor, but for 
 sundry purposes, ordinary paste-boards, etc., it still finds 
 employment. 
 
 In connection with the fibring arrangement in use until 
 recently and previously described, C. Kleine and Ernest 
 Kirchner have patented a method in which a rapidly rotat- 
 ing, so-called twirler is connected with an improved ma- 
 chine. The description reads as follows: According to the 
 present invention the boiled stuffs, superficially washed in 
 the digester or in special leach troughs, are drained off, 
 dam ), or by adding of water in a moderately wet condition, 
 are fed through funnel T (fig. 105) and by the worm B to a 
 twirl, increasing towards the back, making about 300 revo- 
 lutions. The twirl revolves in an entirely closed box of 
 quadratic cross section with blunted corners below widen- 
 ing towards the back like the twirl. The damp or moder- 
 ately wet stuff, regularly fed through T and by B, in so far 
 as it is entirely boiled soft, is now by the arms of the twirl 
 beaten into flakes or stiff paste, while insufficiently boiled 
 or hard particles are completely separated from good 
 fibres, but otherwise left whole. The screw-like arrange- 
 ment of the arms and the widening of the box towards the 
 back effect a gradual moving of the stuff to the opening 
 provided at the widest part of the box, where the good 
 stuff, together with the impurities leaves the twirl, as 
 shown in the illustration, to reach through a drop-pipe or 
 a special transporting arrangement the wash and cleaning 
 arrangement. Here the damp, flaky, or thick and pasty stuff 
 is diluted by plenty of water from the upper sprinklers E 
 
192 THE MANUFACTURE OF CELLULOSE. 
 
 and further divided by a mill-work arrangement C, where- 
 by the large impurities are left whole. The latter settle 
 to the bottom in the deep troughs by the water entering 
 from the lower sprinklers E, i. e., by hydrostatic pressure, 
 they are freed from any adhering good fibres and then re- 
 moved to side tanks by mechanism H, similar to chain- 
 pumps. Floating, light impurities are retained by wire 
 nets at D; heavy particles, carried along, perhaps by the 
 current and motion of the liquid, settle again in the 
 troughs F and H, rinsed by water further entering from 
 below, from where they are removed in the same manner. 
 The now very wet stuff passes a sand fang K, of known 
 construction; by one or several wash drums L, which are 
 arranged directly in cavities of the trough, they are ener- 
 getically washed and thickened. The thick tuff is now 
 completely beaten or disssolved in single fibres by a mod- 
 erately quick rotating rake-roller M with base-rake. 
 
 After leaving back of the rake-roller the stuff is again 
 much diluted by a sprinkler, passes again a sand fang K2 
 and several troughs 1ST, where through the sprinklers Gr, ar- 
 ranged below water, enters again. Thus the heavy parts 
 yet contained settle in the troughs N, against the hydro- 
 static pressure, while the good fibres flow on. The latter 
 again pass a sanclfang, are a second time washed energetic- 
 ally by one or several wash drums and finally reach the 
 stuff press., the setting boxes or the bleach hollander. 
 
 Because the splinters, as undissolved fibre bundles, as a 
 rule are rather wide, but very thin, they pass easily through 
 all these processes and through the fine slits of the knot- 
 fangers, it is therefore recommended to pass the stuff 
 through a refiner, the semi-circular slits of which are cut 
 1 centimeter deep. The refiner entirely dissolves the 
 splinters and if managed rightly makes the fibres uniform, 
 without injuring them. When the stuff is refined and thus 
 free of splinters-, it is very easily bleached and can be used 
 for the best papers. The bleaching of sulphite stuff costs 
 then not more than 2 to 3 marks per 100 kilo. 
 
 As by the best executed washing of the cellstuff, the 
 brown digested solution, soaked inside the single fibres, 
 can be removed but with difficulty, it is advisable to throw 
 the stuff out after washing by a centrifuge. By this pro- 
 cedure the last traces of leach are removed and the stuff is 
 more than otherwise susceptible to bleaching. 
 
THE MANUFACTURE OF CELLULOSE. 
 
 193 
 
194 THE MANUFACTURE OF CELLULOSE. 
 
 In poorly boiled cellstuff and especially waste, according to 
 Mitscherlich, pieces often occur which are not sufficiently 
 boiled, which still contain much resin and which work badly 
 in mill, hollander and paper machine. It has been recom- 
 mended to boil these pieces with 1 1-2 per cent, of the dry 
 weight, with soda in the form of balls for two or three 
 hours under 1 to 1 1-2 atmospheres pressure, whereby the 
 resin is dissolved; also when milling such bad pieces, 1 1-2 
 to 2 liter of soda and 3 liters of petroleum is added to 100 
 Kg dry stuff. The mass must then be washed out in the 
 wash hollander adding 1 to 1 1-2 liter of muriatic acid per 
 100 Kg stuff. Instead of the digester a large barrel with 
 stirrer may be used, the contents of which can be boiled for 
 two to three hours. 
 
 According to a method of Edward Partington, recently 
 patented in England, the tar-like traces of resin often 
 strongly adhering to the sulphite stuff may be removed by 
 paraffin oil or any other carbon-hydrogen combination 
 which is added to the stuff in the wash hollander. For 
 1,000 Kg dry stuff Partington recommended 7 to 9 liters of 
 ordinary paraffin oil of 0.8-0.85 specific gravity, the point 
 of inflammability lays between 17 and 490C. 
 
 VI. OFFENSIVE WASTE-WATER AND ITS PURI- 
 FICATION, CONTAMINATION OF THE AIR, PRE- 
 CAUTIONARY MEASURES, STATUTES OF THE 
 LAW. 
 
 More than by the difficulties of the very manufacture of 
 cellulose, more than by the injurious influence of the sul- 
 phurous acid on all iron parts and on the durability of the 
 digesters, more than by the damage done to the vegetation 
 of the neighboring lands by the gaseous sulphurous acid es- 
 caping from the towers, more, much more trouble is caused 
 to the manufacturer by the offensive waste waters, where 
 the factory is not favorably situated to get rid of them 
 conveniently and possibly unnoticed. The amount of the 
 waste leaches and wash waters is so large, and the quantity 
 of sulphurous acid still contained therein so considerable, 
 besides the color so intense and the smell so disagreeable, 
 that a large river would be required to let all this waste go 
 directly into. But even then it would -scarcely go without 
 complaints, suits and damages, as the fishes especially are 
 
THE MANUFACTURE OF CELLULOSE. 195 
 
 sensitive to the least traces of sulphurous acid and easily 
 become extinct. Therefore, when planning new cellulose 
 factories, it must be considered essential that facilities for 
 letting off the waste waters exist, either by suitable quality 
 of the soil or by large water currents of velocity, and the 
 inlet of the waste water must not take place close above a 
 city, but below, as otherwise the molestations would never 
 cease. 
 
 For a boiler according to Mitscherlich, taken for a basis, 
 every four days and a half there must be disposed of 60 
 cubic meters of leach, just as much or more rinsing water 
 and the still larger quantity of wash water. The off-leach 
 is boiling hot when discharged and the running water also 
 goes off quite warm. According to an analysis one liter of 
 leach contained: Sulphurous acid, 3.86 grammes; sul- 
 phuric acid, 7.33 grammes; chlorine, 0.29 grammes. The 
 residue dried at 110° C weighed 109 grammes. After cal- 
 cination there remained a residue of 19 grammes, contain- 
 ing: Iron oxyde, 0.02 grammes; lime, 10.30 grammes; 
 magnesia, 0.30 grammes; potash, 0.28 grammes; soda, 0.10 
 grammes; a total of 11 grammes. There were consequent- 
 ly contained in one liter of leach: 90 grammes organic 
 constituents, in one cubic meter therefore, 90 kilo; and in 
 60 cubic meters or one digester charge, the collossal 
 amount of 5,400 kilos. This result would have caused sur- 
 prise if the author had not himself ascertained by many ex- 
 periments that for 100 kilos of finished cellulose 291 kilos 
 of absolutely dry wood are required. Almost two-thirds 
 are consequently lost, and these are made up by the knots, 
 loss of fibre in manufacturing and the incrusting constitu- 
 ents, which reappear in the leach. Such an enormous 
 amount of organic constituents, which color the leach quite 
 dark brown, must certainly, even without considering the 
 presence of sulphurous and sulphuric acid, cause a strong 
 contamination of the water currents and must also in short 
 time penetrate the soil of the environment of a cellulose 
 factory, if, as is done as a rule, the leach is let off into a 
 so-called leach pond. In consequence of the standing still 
 in the soil, the leach will then soon grow rotten and, where 
 perchance appearing, gives out a sickly smell. By this pen- 
 etrating through the soil and all joints of mason work, etc., 
 it is then quite obvious that all wells, nearby at least, 
 which are either for domestic use, or furnish the water for 
 
196 THE MANUFACTURE OP CELLULOSE. 
 
 manufacturing, are easily ruined, and that therefore all 
 possible protective means must be provided in order to ef- 
 fect absolute isolation. It is best to take care, when plan- 
 ning a factory, or better still when buying and selecting 
 the site that the field, if not immediately situated on a 
 large river, be somewhat hilly, so that at least the neces- 
 sary water for manufacturing can be taken from the high- 
 er lying part, while the wastes should be let off or sunk as 
 far as possible from the factory. No matter how large the 
 river, the leach must not be run off at once, but, as" the dis- 
 charging of the - digesters is repeated at certain intervals, 
 the regularly renewed quantity must be led off in a small 
 current, or during the night, which is best done by means 
 of a gate regulated by a float; besides, however, the 
 waste being composed of three parts, the digester leach, the 
 rinsing water and the washings, the cooling off of the first 
 two must be effected before. Therefore large cemented 
 basins must be built or deep pools have to be dug and 
 the leach and washings be let in there. Both wastes may 
 also be collected separately. But because these steaming 
 wastes still contain much sulphurous acid, which, if freely 
 streaming into the air, would not only contaminate the sur- 
 rounding atmosphere, but would also injure the vegetation 
 of the neighborhood, the pools must be well covered, and 
 this is best done by beams, laid over with bark and a layer 
 of bark chips, which again are covered witl earth. This 
 best keeps tight and can be easily kept in repair. 
 
 As for the washings which contain traces of sulphurous 
 acid, it is generally sufficient to conduct it away, as far as 
 possible, through several basins, which by dividing walls 
 are separated into several compartments. Then the fine 
 cellulose particles carried along, which perhaps have passed 
 a large stuff fang which the washings must first pass shall 
 next settle. The stuff fangs may be rotating, or large flat 
 boxes covered with fine wire netting. It is well to set into 
 the first compartments bundles of brushwood, which easily 
 retain the cellulose fibres and in a following compartment 
 to let the water through a layer of limestone, mixed with 
 pieces of manganese, whereby sufficient neutralization 
 takes place. 
 
 But if, however, the water current at which the cellulose 
 factory is situated is insignificant the discharge therein of 
 all wastes will cause such contamination that complaints 
 
THE MANUFACTURE OF CELLULOSE. 197 
 
 will never cease and the stepping in of the authorities 
 would necessarily ensue. Unfortunately it is very difficult 
 to render harmless the sulphurous acid. The different ex- 
 periments of chemicals and also all present methods of Al- 
 teration, which with the dirty waste of other factories were 
 yielding good results were of no success with the digester 
 leach, as the disagreeable brown color could not be got rid 
 of. Where therefore direct off-let into the river is not per- 
 mitted, and sinking through sandy soil is not sufficient, 
 nothing else is left to do but to dig several deep shafts 
 down to the ground water and to let into these the cooled 
 leaches and eventually the washings. This can only be 
 clone when the factory is situated quite isolated and human 
 dwellings and wells are far distant in the direction of the 
 descending ground water. But also in this case neutraliza- 
 tion must be cared for. A method of chemist Leisenberg 
 in Halle accepted by the government authorities and tried 
 for some years, in cases where the leaches and rinsing are to 
 be let through shafts to the ground water and the wash 
 waters into the creek is as follows: Inside the factory, best 
 in the washroom, are put up as high as possible three iron 
 or wooden tanks, which all have water supply pipes, can be 
 heated by steam and have stirring arrangement. The latter 
 can also be susbtituted by a steam injector, as furnished by 
 Koerting in Hanover, which permit forcible stirring of the 
 liquid in the tanks. In the largest of tanks, of about four 
 cubic meters, milk of lime is prepared; in the second fer- 
 rite and in the third aluminate is dissolved. All three liq- 
 uids are steadily kept stirred up by the steam injector or 
 other stirring arangements. A pipe about 50 mm wide, 
 which can be closed by a cock, leads from the lime tank to 
 the point where the waste enters the above described waste 
 pool, so that the stream of lime milk, uniformly running 
 off, regulated by the cock can mix as thoroughly as possible 
 with the wastes. The outlet pipes of the two other tanks 
 discharge at a somewhat distant point of the pond and in 
 a continuous weak current add the two other solutions to 
 the waste already neutralized by the milk of lime. This 
 method requires that the waste flow a distance of 100 
 meters or more, that it flows through one or more deep 
 pools, where the current is so low that the lime can practi- 
 cally settle in there before the purified wash water can en- 
 ter the river. It has been found that this method frees the 
 
198 THE MANUFACTURE OF CELLULOSE. 
 
 wash, water of almost every injurious effect, as it does not 
 become rotten or foul even standing for weeks. At the 
 same time the color also becomes somewhat lighter. The 
 same manipulation is employed in discharging the leach 
 into the leach pond, but as this discharging is only done at 
 greater intervals one large tank suffices there in which suc- 
 cessively the lime, ferrite, and aluminate are dissolved and 
 from there are mixed with discharging leach and the rins- 
 ings. 
 
 In cases where a sinking of the leach or dropping to the 
 ground water is not possible or permitted by the authori- 
 ties evaporation is the only remedy. The author has con- 
 sequently tried this experiment in large vessels and by add- 
 ing sulphuric acid has quickened the expelling of the sul- 
 phurous acid. He obtained a thick, syrup-like mass which 
 after cooling became stone hard and could be broken. For 
 practice on a large scale the evaporating tower of R. 
 Schneider, as represented in fig. 20, would best suit for the 
 purpose of evaporation. But unfortunately the plant is too 
 expensive, as the product of evaporation cannot be used 
 with profit, as in the regeneration of the soda. The resi- 
 dues of evaporation do not even have a higher fertilizing 
 value. These residues of evaporation have been recom- 
 mended as feed stuff for stock, used either alone or mixed 
 with other feed stuff, but the author has not learned that 
 experiments have led to any practical results. 
 
 Dr. Frank, at the conclusion of a lecture already men- 
 tioned, is of the opinion that the feed value of the evapor- 
 ated, or at least concentrated leach is not small, as for in- 
 stance 16-18 per cent, of sugar are contained therein; but 
 there is no way yet to utilize the leach fitly, besides the 
 transportation of the leach would be too expensive and the 
 evaporation so much more costly. Nothing else is left to 
 do at present but, according to Frank's method, to remove 
 as much as possible the sulphurous acid and eventually, 
 where it can be done, to use the purified leach for the ir- 
 rigation of meadows and fields, whereby at the same time 
 the difficulty existing with many factories of getting rid of 
 the leach would be removed in the most simple manner. 
 The carbonhydrates, sugar, etc., which in comparison with 
 their high food value have but small fertilizing value, 
 thereby yield little, but the mineral constituents of the 
 
THE MANUFACTURE OP CELLULOSE. 199 
 
 wood, dissolved in the leach, directly benefit the vegetable 
 growth. 
 
 One cubic meter of pine wood (quite dry) for instance 
 weighs about 450 kilometer and furnishes 4 to 5 kilos of 
 clean ashes, corresponding to about 20 to 25 kilos ordinary 
 impure wood ashes; consequently to every one who is 
 acquainted with the utmost favorable yield of wood ash 
 fertilizing for feed crops and especially for acid meadows, 
 the advantage of rational irrigation will be clear. The re- 
 peatedly mentioned Frank method for purification of the 
 leach, which is combined with the recovery of the sul- 
 phuric acid, consists, according to his own statements, of 
 the following: The sulphurous acid brought into the di- 
 gester with the sulphite leach is only in a small part con- 
 sumed and chemically changed in the process of cellulose 
 making, while the larger part, about 70 per cent., is sep- 
 arated in the form of monosulphite, part of it escaping in 
 gaseous form, which part of it together with the leach in 
 which it is dissolved, is carried to the water currents. As 
 then the sulphurous acid in gaseous form as well as that 
 conducted away with the leach, can become very trouble- 
 some to the neighborhood of the factories and injures not 
 only man, but also plants and animals. By it manifold 
 and sometimes quite trying disadvantages have been 
 caused to the management. Mitscherlich has endeavored 
 to do away with the inconvenience caused by escaping of 
 the sulphurous acid with the vapors, by conducting them 
 into the towers. Owing, however, to the great rapidity 
 with which the vapors enter their absorption in the towers 
 is insufficient, especially during the hot season, and the 
 same can be said of the condensation of the vapors, which 
 is employed by factories not equipped with towers. In re- 
 gard to the leaches, which, because of their high amount 
 of organic substances are very troublesome in smaller wa- 
 ter currents, there has not yet been found a practically 
 useful method to free it from its amount of sulphurous 
 acid and other injurious substances. The evaporation of 
 the leaches, taken up by several factories, has proved to be 
 a very costly make-shift on account of the rapid destruc- 
 tion of the evaporating apparatus,, the enormous consump- 
 tion of coal and the absolute worthlessness of the residues 
 of evaporation as fuel, the more as with the very evapora- 
 tion the sulphurous acid is carried along into the air. 
 
200 THE MANUFACTURE OF CELLULOSE. 
 
 In his method Dr. Frank endeavors to remove only those 
 constituents of the leach, and vapors which are proven to 
 act injuriously. As such, besides the sulphurous acid and 
 its combinations in solution he names the aldchyds con- 
 tained in the leaches and finally the dissolved resin and 
 tar-like substances, which in later separating becomes in- 
 jurious to the gill breathers, as to the plants by excluding 
 the air. As Dr. Frank has proved in an expert report the 
 other constituents of the leaches, mostly sugar and am- 
 gloides, also the mineral constituents of the woods, are not 
 only entirely harmless and well suited for the nurishing of 
 animals and plants, but also, as far as they are of organic 
 nature, rapidly and completely removed, even in quite 
 small water currents by oxydization. 
 
 However, in order not to make the purification of the 
 leaches too expensive Dr. Frank combines this method with 
 the recovery of the sulphurous acid which, together with 
 resins, dye stuffs and nitrogenous constituents \he precipi- 
 tates in the form of the almost insoluble mono-sulphate of 
 lime. Then the liquid freed from its injurious constitu- 
 ents is submitted to a further chemical treatment with air 
 and carbonic acid, whereby besides the oxydation of the 
 aldchyds,, also the small amount of mono-sulphite in solu- 
 tion is transformed into the entirely harmless sulphite of 
 lime (gyps). 
 
 The precipitate of sulphite of lime, as obtained is very 
 impure. After settling, according to Dr. Frank's patented 
 method, it is freed from the organic substances and then 
 yields a perfectly pure sulphite of lime, which stirred up 
 with water and charged to Frank's leaching apparatus is 
 worked into a leach perfectly equal to a fresh sulphite solu- 
 tion by simply treating with sulphurous acid. 
 
 As a minimum saving, obtained by this method of re- 
 covery, Dr. Frank guarantees 33 per cent, of that qauntity 
 of sulphur which was necessary for the sulphite solution 
 originally charged to the digester, so that, when 17 kilos 
 of sulphur were necessary per cubic meter of leach without 
 recovery, with his method of recovery this consumption is 
 reduced to two-thirds or about 11 kilos; thus bringing the 
 total cost, per cubic meter sulphite leach down to 33 per 
 cent. 
 
 However, as the quantity of sulphurous acid left un- 
 changed in the digesting process, theoretically estimated, 
 
THE MANUFACTURE OF CELLULOSE. 201 
 
 amounts to about 70 per cent., with careful management 
 of the recovery it can he expected to recover from the sul- 
 phite leaches up to about 50 per cent, of the sulphurous 
 acid and thus to reduce the supply of sulphur material one- 
 half. 
 
 The installation of Frank's method for the purification 
 and recovery of the leaches, in consequence of the expert 
 opinion of the reputed chemists, Professor Dr. Medicus and 
 Professor Dr. Engler has been officially ordered for the 
 cellulose factory in Aschaffenburg, and on account of the 
 entirely satisfactory results obtained the protests and com- 
 plaints raised against the working of the factory were non- 
 suited in all instances. The factory in Aschaffenburg gives 
 the daily expense of the method as 12 marks, the value of 
 the recovered sulphur material; as 35 marks, the recon- 
 sumption of the latter; as 40 per cent., so that besides the 
 removing of the formerly existing difficulties in regard to 
 running off the leaches there is left a daily surplus of 23 
 marks, amortizating within a short time the cost of the 
 plant. According to the statement of the inventor, there 
 are at present in Germany, Austria and Sweden a large 
 number of factories engaged to install his method and for 
 the new cellstufT plant of the Munkedal, Achtiebolag, Ud- 
 devalla, Dr. Frank has even accepted guarantee for the 
 fish stock of the mill creek, separated by a grate. 
 
 Dr. Frank's method for the purification of the leach and 
 recovery of the sulphurous acid thus appear to be, for the 
 cellstuff factories as well as for their neighbors an equally 
 benefitting solution of the perplexing question. 
 
 A perfect conclusion of the wash water question will, 
 however,, not be reached until the utilization of the carbo- 
 hydrates, so liberally contained in the leaches, for feeding 
 purposes. The composition of the leaches, freed from the 
 sulphurous acid and the resins, according to his investiga- 
 tions, comes near to that of the molasses residues, but 
 against the latter has the advantage of containing more 
 sugar (up to 18 per cent of dry substance) and less salts. 
 The production of aniline, contemplated by some, as well 
 a.? its employment for the manufacture of alcohol, acetic 
 acid and naptha, if paying at all, requires a complicated 
 plant, so that for the present it will be well to rake in con- 
 sideration only its agricultural utilization, as feed for the 
 stock, or its use for irrigating ari fertilizing fields and 
 
202 THE MANUFACTURE OF CELLULOSE. 
 
 mefiows. The possibility of preparing substances useful 
 in the arts from the material is still left open. 
 
 The agricultural utilization left entirely out of the ques- 
 tion the method is, however, practical for all those factor- 
 ies which for the present have difficulties on account of 
 running off the leaches, as the leaches freed from their 
 directly" injurious constituents and also of 
 proteids give little cause for processes of 
 fermentation and purification, as well as for the 
 formation of algae, and even in moderate dilution 
 in small flowing waters suffer rapidly a complete oxydation 
 and self-purification which is prevented or much retarded 
 by the presence of sulphurous acid. Besides the unpurified 
 leaches, containing about 0.6 to 0.75 per cent, of sulphur- 
 ous acid, according to the experiments of Dr. Weigelt-Eu- 
 fach, when let into waters used for fish culture, require a 
 dilution, corresponding to about 1,500 times its own vol- 
 ume. For a digester charge of 60 cubic meters, in order to 
 satisfy these demands, 90,000 cubic meters of water must 
 therefore be used, a quantity not everywhere attainable. 
 
 In addition to this it may be mentioned that the unpur- 
 ified wastes certainly favor the formation of algae in the 
 river bed, and that especially with small water currents 
 the disadvantage comes so much more to light as a direct 
 contamination by cellulose fibres can be seen. These algae 
 form principally during the cold season], and disappear al- 
 most entirely in summer. If, however, once present, they 
 can scarcely be eliminated even if the supply of leach ceas- 
 es entirely. The author has observed that five years after 
 the closing of a factory the algae reappear regularly in the 
 bed of the river during winter. 
 
 In the soda oellstuff manufacture the waste leaches can 
 also be used for the preparation of stock feed. A Mr. 
 Voigt has taken out a patent for this, TSTo. 33,235, and gives 
 the following as his method: The incrusting constituents 
 of the straw and likewise of the wood (consisting of carbon- 
 hydrates, proteins, etc.,) received by the animal make up 
 the nutritive part and are completely assimilated by the an- 
 imal organism and transformed into flesh and fat. The in- 
 ventor therefore aims to recover in the form of press-cakes 
 these very important, nutritious products, which in cellu- 
 lose manufacture by means of soda enter into the alkaline 
 leach. After the process of digesting is finished the alka- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 203 
 
 line liquid, much admixed with organic matter, is heated 
 with sulphuric acid until neutral, whereby under formation 
 of sulphate of soda (Glauber's salts) all organic matter dis- 
 solved in the alkaline liquid (with the exception of some 
 coloring matter) separate in the form of a most finely di- 
 vided precipitate. This precipitate is then separated from 
 the sodium-sulphate solution by means of a filter press, 
 then once more washed with water and again pressed and 
 so dried in the shape of cake and brought into trade. The 
 
 Fig. 106. 
 
 product thus obtained is of a pleasant scent and taste, re- 
 sembling fresh hay and is readily eaten by horses, cows and 
 sheep. On account of its fine division, as well as of its nu- 
 tritive constituents, it is almost entirely assimilated by 
 the animal organisms, and may take a conspicuous place 
 among the food essences now existing in commerce. 
 
 In regard to the so-called mother liquor (sodium sul- 
 phate solution) still left it is evaporated in an evaporating 
 
204 THE MANUFACTURE OF CELLULOSE. 
 
 pan to crystalization, and as crystal Glauber salts 
 brought into commerce. According to the view of others 
 the food obtained by Voigt's method is not a food essence 
 in the economical agricultural sense of the word, as it does 
 not contain proteins (albuminates) as these have already 
 been decomposed when boiling the wood with the caustic 
 leach. They admit, however, that the food is useful. 
 
 To prevent the injurious effect of the leaches, Alexan- 
 der Kumpfmiller and E. Schultgen obtained a patent (D. 
 R. P. No'. 81,338) on the method described below: 
 
 The waste leaches coming from the digesters, from the 
 vessel A, Fig. 106, continuously now into the tower B, 
 which is filled with a rack of stones and serves to warm the 
 waste leach, and at the same time to cool off the roast- 
 ing shells. A distributing arrangement causes the leaches 
 to drizzle evenly through the whole cross section of the 
 tower ; and they collect in the receptacle F. At the foot of the 
 tower the hot roast g-ases from the pyrites oven D enter 
 through pipe E into the tower, give off their heat to the 
 leaches drizzling down and, cooled, leave the tower through 
 pipe C, which conducts them to the absorption apparatuses. 
 
 By the action of the roast gases on the leaches a reaction 
 takes place between the sulphuric acid contained in the 
 former and the sulphite acid contained in the latter ac- 
 cording to the equation: 
 
 SO 3 plus Ca S03 plus H20 equals Ca S04 plus S02 plus 
 H20. 
 
 Consequently the sulphurous acid combined with lime, 
 contained in the leaches, is liberated, while at the same 
 time the roast gases are freed of sulphuric acid, whereby 
 the formation of gyps crusts in the lower parts of the ab- 
 sorption apparatus is avoided. 
 
 From the foot of the tower the hot waste leaches are 
 raised through pipe G- into a vacuum apparatus H and as a 
 thickened liquid continuously flows through pipe K into 
 the reservoir J, placed about 10 meters below. 
 
 With the spray, evolved under the influence of the vac- 
 uum in the spray condensor L, which is fed with lime wa- 
 ter, the steam vapors are condensed and the sulphurous 
 acid is absorbed. The water of condensation therefore, af- 
 ter previous cooling, can partially again be used for feed 
 water, partially, as so-called half leach, it can be pumped 
 to the absorption towers. 
 
THE MANUFACTURE OF CELLULOSE. 205 
 
 Two spray condensers can be used; in this case the one L 
 is fed with water for the condensation of the steam vapors, 
 the other L, with lime water, to bind the sulphurous acid, 
 so that the sulphite of lime formed is collected in reservoir 
 III, separately from the water of condensation. 
 
 The ejector N serves to produce the vacuum, when 
 starting the plant; it can also be employed to conduct the 
 sulphurous acid gas from escaping from the first condensor 
 immediately into the pipe C. 
 
 A new patent for the utilization of leaches has been tak- 
 en out by the stock company Xylolyse and Dr. Emil Meyer 
 in Berlin (D. E. P. No, 45,951) for a method for the pro- 
 duction of liquid products of distillation from cellstuff 
 leaches. It reads as follows: In the production of cellstuff 
 from wood almost one-half of the weight of its dry sub- 
 stance is brought in solution by the leaches. By supplying 
 heat by means of steam coils the waste leach from 
 the soda process can be condensed down to 35° B. 
 The condensed leach is mixed with 40 to 
 55 parts by weight with charcoal, and then formed 
 in uniform, durable and transportable pieces, permitting 
 further drying in heating chambers, or they may with the 
 original amount of water at once be charged into red-hot 
 retorts, without damaging by sudden cooling off and with- 
 out losing their form in charring. 
 
 The distillation, damping and cooling of the residue 
 charcoal, the collecting of the tar, the gas water and the 
 gases differ in no wise from similar known processes. Only 
 the product of distillation itself differs from that of the or- 
 dinary charring of wood in retorts, in so far, as formic 
 acid, acetic acid:, etc., do not appear, but only methgl-al- 
 cohol, etc., and diverse amine combinations are dissolved 
 in the water of condensation; also a tar of different quality 
 is obtained from this resulting to the management the ad- 
 vantage that instead of copper for the rondensors iron can 
 be used and in rectification of the gas water its volatile, 
 valuable products can be obtained by distilling off a small 
 quantity. 
 
 If the acid leaches of the sulphite process are intended 
 to be worked in this manner the free acid must first be 
 eliminated. Further because the lime in solution in ac- 
 cumulating would in the end disqualify the coal residue, it 
 is to be recommended to precipitate it as sulphate by add- 
 
206 THE MANUFACTURE OF CELLULOSE. 
 
 ing glaubor salts, which can always be recovered. 
 
 When distilling the sulphite leaches and also the alka- 
 line leaches of the so-called sulphate cellulose containing sul- 
 phide of sodium, besides the aceton and the methyl alcohol, 
 other volatile, sulphuric cercaptanic ahd alkylthio-car- 
 bonic combinations' are formed which are neither com- 
 pletely condensed nor are they made harmless when burned 
 with the resulting gas, with which they are mixed. 
 
 Another utilization, or rather recovery of spent sulphite 
 leaches, is done by apparatuses which are built by- the Qot- 
 zern Machine Works. 
 
 In the sulphite stuff manufacture a liberal third of the 
 sulphurous acid gets lost, about one-sixth is retained in the 
 leaches and runs off with the washings; and just as much 
 escapes with off-vapors into the atmosphere. In this manner 
 scarcely two-thirds of the sulphurous acid charged to the di- 
 gestor are utilized, and sometimes still less. 
 
 To remedy this disadvantage, Director Rudulf Kron, in 
 Golzern, has invented a simple plant for the purpose of the 
 recovery of sulphurous acid contained in waste waters and 
 in the off-vapors. The practical trial also yielded a saving 
 of sulphur 30 to 40 per cent, equal to a price reduction of 
 from 5 to 10 marks per ton of cellstuff. At the same time 
 the present rather general contamination of the. atmos- 
 phere and of the factory water is prevented. 
 
 The Papier Zeitung publishes another method for the 
 purification and utilization of the leaches, resulting from the 
 manufacture of sulphite stuff, by Viggo Beutner Drewson. 
 The method consists in the treatment of the spent leaches 
 with caustic lime, if possible free of carbonic acid, at higher 
 temperature and with the application of pressure. 
 
 If the leach used in the sulphite stuff manufacture, which 
 possesses a distinct acid character, is treated with caustic 
 lime at ordinary temperature, it combines with the present 
 sulphurous acid to make lime monosulphite. The leach liquid 
 of now-changed condition has lost the capacity to hold in 
 solution part of the organic substances, which were dissolved 
 in the acid solution, and they are precipitated, together 
 with the lime monosulphite. The process results at boiling 
 temperature in the same manner as at ordinary tempera- 
 ture. 
 
 Quite different, however, is the result of the action of the 
 
THE MANUFACTURE OF CELLULOSE. 207 
 
 caustic lime on the sulphite leach, when both are heated to- 
 gether to higher temperature under pressure in a closed ves- 
 sel, because then the lime is able to decompose the organic 
 combinations dissolved in the spent leach, originating from 
 the incrusting substances of the wood. If, then, the bottom 
 sediment, obtained by treating the spent leach with caustic 
 lime at about 6 atmospheres pressure and treating it with 
 muriatic acid, is filtered off, considerable quantities of sul- 
 phurous acid escapes, while at the same time a bottom- 
 sediment of organic substances insoluble in water and acid 
 is left contaminated with sulphate of lime. The light yellow 
 leach, filtered off from the original bottom-sediment, pro- 
 duced by the caustic lime, when evaporated, leaves but a 
 small fraction of the substances contained in the spent leach, 
 because the more readily decomposed sulphur substances as 
 well as the principal amount of the organic, so called incrust- 
 ing substances, are precipitated. Operating with this process 
 it is therefore possible, with such a cheap material, as given 
 in the caustic lime: (1) To purify the spent leaches, and to 
 dispose of them in a simple and harmless manner; and 
 (2) to produce substances of material importance to the arts. 
 In practice the present method is carried out as follows : 
 After the finishing of the digesting process the spent 
 leach is charged under pressure into a closed vessel, provided 
 with a stirrer, in which is contained already the required 
 amount of caustic lime, as much as possible rid of carbonic 
 acid. Because of the immediate neutralization of the acid, 
 this vessel may be of iron. As soon as the spent leach has 
 all been blown over into the vessel, steam is admitted, the 
 stirrer is set in motion, and the temperature is maintained 
 at a certain height corresponding to about 6 atmospheres, 
 until a test indicates that the reaction is finished. As soon 
 as this is the case the contents of the vessel are filtered by 
 a filter press. The light yellow liquid of alkaline reaction 
 running off is, when necessary, treated with carbonic acid 
 by passing over it. the products of combustion from a chimney 
 by means of a koerting injector, to neutralize the alkalinity. 
 The filtered off bottom-sediment, consisting of calcium- 
 monosulphite, calcium-sulphate and of the lime combina- 
 tions of the organic substances formed from the incrusting 
 substances of the wood, is then used in place of limestone or 
 limemilk for preparing the bisulphite leach. In treating 
 
208 THE MANUFACTURE OF CELLULOSE. 
 
 with sulphurous acid there are left indissolved principally 
 the organic combinations which are filtered off in a filter 
 press, while the filtrate is returned for use in boiling wood in 
 the manufacture of sulphite cellstuff, exactly like the ordi- 
 nary bisulphite leach. 
 
 In this manner one-fourth to one-half of the original 
 amount of sulphur is recovered. The organic substances, se- 
 cured by this method, can be used for different purposes. 
 
 For a clear illustration of the correctness of the above- 
 mentioned proposition of Dr. Frank, to use the purified 
 wastes for irrigation, and thus at the same time causing self- 
 improvement of contaminated river water, a case from prac- 
 tice may serve. It is about the contamination of a small 
 creek, in total carrying capacity about one cubic meter of 
 water per minute, by the spent liquors of a sulphite cellulose 
 factory. Dr. Frank had been appointed expert to give his 
 opinion whether the complaints that the water be fit neither 
 for domestic purpose, nor for the irrigation of meadows, 
 were just, and whether a remedy could be had. It is now 
 scientifically proved that water contaminated with organic 
 matter in solution in long contact with air, especially witii 
 much fall, is again purified, that consequently in this pro- 
 cess the oxygen dissolved in water proves to be more active, 
 than the less active oxygen of the air. But as water in the 
 presence of sulphurous acid cannot contain oxygen, the self- 
 purification of water mixed with larger quantities of sulphite 
 leach would be but insignificant. Nevertheless, even in this 
 unfavorable instance, a decrease of the organic matter with 
 simultaneous oxidation of the sulphurous acid to sulphuric 
 acid can be proved. The following analyses serve as vouchers 
 for this: 
 
 Sample 1. The creek water, when entering the factory, 
 contained in one million parts a total residue per liter of 
 150 mg. ; of this : organic matter 78, lime 42, sulphurous 
 .acid 0. 
 
 Sample 2. Mixture of leach and leach wash-water, when 
 leaving receptacle, contained in one million parts a total 
 residue of 58,450 mg. ; of this: organic matter 42,200, lime 
 5,658, sulphurous acid 1,669. 
 
 Sample 3. The creek water, taken 5 kilometers below the 
 factory, contained in one million parts a total residue of 
 1,600 mg. ; of this : organic matter 600, lime 184, sulphurous 
 acid 35. 
 
THE MANUFACTURE OF CELLULOSE. 209 
 
 A further effective purification, scarcely worthy of con- 
 sideration in currents with abundant water, would be ob- 
 tained in this case by employing the small creek for irri- 
 gation purposes, because the soil, by its absorbing and oxy- 
 dizing influence, not only diminishes the organic matter, 
 but also the amount of lime. In this irrigation also the 
 most valuable mineral constituents of the wood, potash, etc., 
 would do good service. 
 
 To test the behavior of purified leaches by experiment, part 
 of the spent leach (Sample 2) was freed from sulphurous 
 acid and resins, according to Dr. Frank's method. Although 
 after this operation the liquid appeared somewhat darker 
 than the acid leach, after diluting with thirty times its 
 amount of water, and longer contact with air, it proved to 
 contain one-half less of organic matter than Sample 3, and 
 also the color was lighter, after adding water. But much 
 more distinctly did the success of the purification appear by 
 this, that, while Sample 3 notwithstanding its high amount 
 of sulphurous acid, inside of two days appeared very turbid; 
 the sample made of purified leach with equal dilution kept 
 perfectly clear for. 8 to 10 days under the same conditions. It 
 was still less difficult to prove by figures and by experiments 
 on a large scale that the recovery of the sulphurous acid con- 
 nected with the purification of the spent leaches, besides 
 covering all expense, yielded a considerable surplus. 
 
 From these experiments it seems : That the waste-waters 
 in question, after they are freed from sulphurous acid and 
 resinous particles, do not in any manner harm the vegeta- 
 tion, but are especially suited for the irrigation of meadow? 
 and fields, because they contain numerous valuable fertiliz- 
 ing substances. Also that the purified waste-waters admitted 
 to the river are not injurious to fish and warm-blooded ani- 
 mals, and are useful for many domestic purposes, as num- 
 berless spring waters, serving to supply cities, show a higher 
 amount of lime than the creek water of Sample 3. 
 
 Then, although larger river currents are at the disposi- 
 tion of most cellulose factories, to receive their wastes, the 
 extreme case here cited proves that only the directly in- 
 jurious constituents need to be removed from the waste- 
 waters of the sulphite leach, while for the removing of the 
 organic matter in solution, sugar, amyloids, etc., in them- 
 selves quite harmless, the energetic self-purification in the 
 river can be counted upon with confidence. 
 
210 THE MANUFACTURE OF CELLULOSE. 
 
 Some instructions by the government, which have already 
 proven successful, are the following : 
 
 The spent leachs, or spent leaches and washings together, 
 are to be treated with caustic lime, so that they are ren- 
 dered almost, but not quite, neutral. The last remnant of 
 acid is to be removed by gradual treatment with limestone, 
 while admitting air. 
 
 To regulate the latter process, impenetrable collecting 
 ponds are to be built, which will hold fourteen times the 
 amount of the daily produced quantity of spent leach and 
 from which it can be run off at the upper edge. 
 
 Drawing off may be done when thorough neutrality of the 
 liquid has ensued, but only into water currents, which cause 
 a dilution five hundred times the off-run. 
 
 Another cause for the contamination of the water in cellu- 
 lose factories is by the pyrites residues stored away in heaps. 
 During heavy rains they are leached out, and the water 
 running off, like the other not purified waste-waters, acts 
 injuriously and must therefore be conducted off in such a 
 way that, together with the other waste-waters, it can . be 
 purified or dropped. The residues themselves make a very 
 good material for roads; because they make such hard roads 
 and do not permit any vegetation to come out. 
 
 When the pyrites residues are heaped up near a river, great 
 damage can be easily done when, during a hood, the residues 
 are carries off over fields and meadows, and thus great sur- 
 faces can for years at least be made partially sterile. 
 
 In the neighborhood of cellulose factories complaints are 
 general about contamination of the air. With the sulphite 
 cellulose factories, especially if no residences are nearby, the 
 evil is not so very bad, as the annoying smell is present only 
 when the necessary care is not taken. 
 
 The soda cellulose factories have .greater difficulties to 
 combat in this respect. When discharging the digester, aud 
 in the process of recovering the soda, gases escape which may 
 be compared to the odor of foul cabbage, and which some- 
 times appear so strongly that the whole country for a great 
 distance, according to strength and direction of the wind, 
 is made to suffer. Notwithstanding the fact that the gases 
 frequently evolved in evaporating the leaches are conducted 
 over fires, and there consumed, the extremely suffocating 
 smell can scarcely be avoided, especially as some manufac- 
 turers are not able even to tell exactly where the principal 
 stench really comes from. 
 
THE MANUFACTURE OP CELlLULOSE. 211 
 
 In consequence of the undeniable harm done the neigh- 
 borhood, in many countries the authorities were prompted 
 to proceed against the cellulose factories in regard to con- 
 tamination of the atmosphere, and indeed at some places 
 this was done in such a manner that the very existence of 
 the factories was jeopardized. This appeared most strik- 
 ingly in the case of the Koeslin cellulose factory, situated 
 1,500 meters distant from the city, and where the government 
 on account of the suffocating vapors for every special in- 
 stance imposed a fine (eventually six days' imprisonment of 
 the manager.) In several instances this fine was also col- 
 lected, although counter-suits were instituted, lasting for 
 years, and although everything was done to diminish the 
 nuisance to the smallest possible measure. 
 
 The many complaints about contamination have now 
 caused the authorities to impose severe conditions for the 
 management of cellulose works. For example, the following 
 for a soda cellulose plant : 
 
 First — The manufacturer has to adhere to the method of 
 manufacture as described by him in all its parts, especially 
 must all operations of digesting, washing and evaporating 
 be conducted in perfectly closed systems. 
 
 Second — All parts of apparatuses (new and old digesters, 
 blow-off cylinders, pipe-lines, etc.), in which are contained 
 liquids heated or treated under pressure, must be made per- 
 fectly tight. At the least untightness noticeable the re- 
 spective part of the apparatus is at once to be cut out and 
 repaired, and not to be put in use again until answering the 
 test described by law (certificate of the boiler inspection.) 
 
 Third — Inside of twenty-four hours not more than eight 
 charges shall be emptied. In order to control this limit of 
 production the respective book of changes must at any 
 time be accessible to the representative of the government. 
 
 Fourth — The conducting of the leaches, from the digesters 
 as well as from the blow-off cylinders to the end-leach re- 
 ceiver, and from thei'e to the closed condensers, must ill 
 through be done in closed pipes. 
 
 Fifth — The end-leach receiver itself must also be hermet- 
 ically closed against the outer air; and the place for the air 
 to enter when blowing off the leach must be provided with 
 an automatic valve opening inside. 
 
 Sixth— The vapors produced in the digester must be blown 
 off continuously and bv a surface condenser with water cool- 
 
212 THE MANUFACTURE OF CELLULOSE. 
 
 ing and. sufficiently large . condensing surface must be con- 
 ducted to two receptacles, in which the separation of con- 
 densed oil and water goes on. The dimensions of these re- 
 ceptacles must be such that a complete separation of the oil 
 takes place, before emptying. This oil must be carried off in 
 well-closed vessels and provision must be made that in sepa- 
 rating the water it does not come in contact with the outer 
 air. The gases not condensed in the coolers must be con- 
 ducted in closed pipes to a fire, and there be entirely con- 
 sumed. From the reservoirs the water left after removing 
 the condensed oil is to be pumped into an apparatus in which 
 by a heating coil the last traces of the volatile oils and odors 
 are expelled, and also burned in a grate fire. 
 
 Seventh — The vapors leaving the second condenser, if still 
 containing uncondensed gases, cannot be used to heat the 
 leach mixture, but must be condensed by themselves, and 
 the uncondensable part, as under sixth, must be burned in a 
 grate fire. 
 
 Eighth — All hitherto mentioned gas conductors, leading 
 under the grate fires, must end in the form of a spray under 
 the middle of the respective fire grates. 
 
 Ninth — The fire-wall, inclosing the ante-room, must be 
 constructed in such manner that it cannot become untight. 
 If untightness should show, no leach shall be evaporated in 
 this ante-room. 
 
 Tenth — The gases from the ovens before entering the 
 chimney must be made to pass a final fire, so that all odors 
 left are consumed. If the ordinary grate fire should not 
 fulfill its purpose with sufficient completeness it is to be re- 
 placed by a regenerative gas fire with highly heated air. 
 
 Eleventh — The lyes prepared for digesting should not con- 
 tain more than 10 per cent, sulphide of sodium of the amount 
 of soda (caustic soda and carbonate of soda figured on the 
 latter) in the leach. 
 
 Twelfth — The observation of all permit conditions, the 
 maximum amount of sodium sulphide of the leaches, as well 
 as the question of retaining and consuming of the odorous 
 gases, is placed under chemical and technical supervision. 
 
 Thirteenth — The wash-waters, yielded in washing out the 
 leaches adhering to the digested wood stuff in the blow-off 
 cylinder, must, before being admitted to the river, be mixed 
 with the spent liquors of the chlorine-bleach. 
 
 The changes made in the soda factory in question con- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 213 
 
 sist of the following: The wood is not boiled to a finish 
 with the same leach, but the leach is gradually circulated 
 in the digesters, being in four different states, so that finally 
 the stuff comes in contact with pure leach. The digesters are 
 no longer blown out into the open, but into closed vessels, 
 and there thoroughly washed out. 
 
 Thereby less but more concentrated leaches are obtained 
 for the calcining process; and, further, the epening of the 
 digesters, filled with hot stuff which was part of the cause 
 of the complaint of the neighborhood, is entirely avoided. 
 The complete combustion of the gases produced in calcining 
 is also aimed at by the calcining oven containing three 
 equally divided fireplaces, so that at the end of the oven 
 all gases must again pass a powerful fire, worked with strong 
 supply of air. Of the products of combustion of this pro- 
 
 P 
 
 r 
 
 Fig. 107. 
 
 cess more than 50 analyses were made in different parts of 
 the oven, and of the chimney at the different states of work, 
 and at different times, because it has been apprehended that 
 hydrogen sulphite could be produced by the dry distillation of 
 sulphide of sodium formed from the sulphate of soda. This 
 presumation, however, has not been confirmed ; sulphide of 
 hydrogen was not formed at all by the analyses, or in such 
 small quantities as found in the products of combustion of 
 every larger coal fire. It could, consequently, not be settled 
 
214 THE MANUFACTURE OF CELLULOSE. 
 
 that the employment of sulphate of soda with the arrange- 
 ments made would cause any additional inconveniences. 
 
 The arrangements as prescribed for rendering harmless 
 the water of condensation originating from blowing-off the 
 digester are illustrated in the sketch (Fig. 107) and for its 
 explanation the following is to be said: After the vapors 
 produced when blowing off the over-pressure of the digesters 
 have been conducted through a condenser, the waters of 
 condensation and the uncondensed vapors are alternately 
 passed through the pipes a a by means of valves b b to the 
 closed iron reservoirs A A. In these accumulates the water, 
 while the uncondensed vapors are through the pipes i i con- 
 ducted under a fire, where they are consumed with a bluish 
 flame. 
 
 While the one reservoir A is filling the other is standing 
 still for 5 to 6 hours; during which time the oily substances 
 separate on top. The latter are then let off by the outlets 
 c c c provided with valves, and burned in a fire. The liquids 
 cleared off in the reservoirs, which always contain odorous 
 substances, are, through the pipe connections d d and e 
 pumped to the closed iron vessels B and heated by the steam 
 coils g g. The last traces of the odorous substances are here 
 volatized and through h reach a fire, where they are also 
 burned up. The spent water, freed from its odorous sub- 
 stances in the vessel B, after it has gone through a process 
 of precipitation and clarifying with caustic lime, is let off 
 through f and re-employed in the factory. 
 
 For the sulphite cellstuff factories, after hearing several 
 experts, more severe instructions were issued by some au- 
 thorities, for which the following points may serve as an 
 example. These were made for the Aschaffenburg paper fac- 
 tory previous to the erection of a sulphite cellulose plant : 
 
 First — The extensions of the factory plant must be exe- 
 cuted exactly according to the plans submitted and under 
 compliance with the instructions of the general building 
 regulations. 
 
 Second — For the additional steam boiler a permit of the 
 Bavarian Association for steam boiler revision must be de- 
 posited in regard to its safety, as well as to completeness and 
 tightness of its armature parts. 
 
 Third — All arrangements, as far as the chemical depart- 
 ment is concerned, must be such that sulphurous vapors can- 
 not escape. Therefore all apparatuses, absorption and di- 
 
THE MANUFACTURE OP CELLULOSE. 215 
 
 gesting apparatuses and all pipe-lines must always be main- 
 tained in condition and the draft in the sulphur pans is to 
 be regulated in such manner that sulphurous acid cannot 
 escape. 
 
 Fourth — The digester-vapors must not escape into the open 
 air when blowing off the boiler, but must be conducted par- 
 tially through pipe-lines which can be shut off partially by 
 putting in injectors; they have to be conducted into freshly 
 charged digesters. 
 
 Fifth — The purification and carrying off of the waste- 
 waters must be done separately from those of the soda cell 
 stuff factory. The diluted spent leaches, before admitting to 
 the Aschaff, must be submitted to Dr. Frank's method of 
 purification, whereas the water coming from the rest of the 
 plant, especially from the wash-hollander, must by means 
 of a special pipe-line, be conducted to the clearing basins, 
 arranged in the soda cell stuff plant. 
 
 Sixth — The number of basins to be put up for purification 
 and clearing of the washed spent leaches is set down at 
 three, with a cubic contents of 60 cubic meters each and a 
 bottom face of about 309 square meters. They have to be 
 put up in such manner that side walls and bottom, in pro- 
 portion to the pressure of the liquid, are sufficiently strong 
 and made watertight, laid with cement mortar, and besides 
 are lined inside with a layer of cement to obtain perfect 
 impenetrableness. 
 
 Seventh- — The precipitates obtained in the purification of 
 the waste-waters, according to Dr. Frank's method, if not 
 utilized as fertilizers, must after drying in the air again be 
 burned. 
 
 Eighth — The letting off of the waste-water from the clari- 
 fying basin must be regulated in such manner that not more 
 than 1.5 liter per second are admitted to the Aschaff. 
 
 Ninth — The circular saws employed in the plant, and all 
 parts of the transmission, as gearing, pulleys, etc., as far as 
 in the reach of the workmen, must be provided with suffi- 
 cient means of protection. 
 
 PLANNING OF CELLULOSE FACTO RIES. 
 
 From a consideration of the different processes of cellulose 
 manufacture as treated in the previous chapters and consid- 
 ering the difficulties and aggravations by adjacent property- 
 holders and the authorities, it will be plain that when newly 
 
216 THE MANUFACTURE OF CELLULOSE. 
 
 planning a cellulose factory the utmost importance must be 
 paid to the right selection of the place. As in cellulose 
 manufacturing there is not a large consumption of power, 
 and the steam engines to-day are built so that the consump- 
 tion of coal is reduced to a minimum, it is not necessary to 
 look for cheap water-power, but rather for the immediate 
 neighborhood of a large river, which facilitates the direct 
 supply of wood or part of it by water, and may also permit 
 the shipping of the finished product, but principally facili- 
 tates the disposition of the waste-waters. 
 
 If possible the lot should not be situated above a city, 
 and not too near a large community, or especially valuable 
 plantations, or parks. When the supply of wood is not pos- 
 sible directly by the river, it is most necessary to be near 
 a railroad and to possess a track if possible right into the 
 with every cellulose factory. In the rarest cases, a factory 
 will be so situated that it may get. its whole supply of wood 
 nearby, i. e., carting it directly from the woods. Almost 
 always the factories are dependent on the supply from 
 greater distances, and it is well, if besides the high railroad 
 freights, the cost of carting from and to the depot has not 
 to be added. It must be considered that every cellulose fac- 
 tory, for instance, figured for but one Mitscherlich digester, 
 for a yearly production of 9,000,000 liters of dry cellulose, 
 about 7,000 volumeters of wood are necessary, which at its 
 mean amount of dryness, alone represents a weight of 
 3,680,000 kilometers. When considering the other mate- 
 rials necessary for the above amount of wood per year, the 
 following statement is obtained : 
 
 Kilo- 
 Materials, meters. 
 
 Wood (7,000 volumeters) 3,680,000 
 
 Cellulose : Dry, 900,000, moist 1,800.000 
 
 Pyrites .' 530,000 
 
 Lime 180,000 
 
 Coal . 1,200,000 
 
 Other materials 110,000 
 
 Total 7,500,000 
 
 From this statement it will be seen that for 100 kg. air- 
 dry cellulose about 58 per cent, of pyrites are used. It is to 
 be remarked, however, that factories with larger plants use 
 
THE MANUFACTURE OF CELLULOSE. 217 
 
 but 50 per cent., or only 45 per cent, of pyrites, according to 
 quality and other circumstances. When employing pure sul- 
 phur, which is better in many instances, the consumption 
 is much less. Herrmann Brungger, according to his experi- 
 ences, states the consumption of 99 per cent, of sulphur, as 
 9.77 kg. for 100 kg. of air-dry cellstuff. 
 
 Therefore, for every single digester at least 7,500,000 kilos 
 of material have to be carried to and from the factory each 
 year, which, even with favorable situation of the factory, 
 gives a high expense for freight ; especially as in recent years 
 the manufacturer cannot evade the request of the customers 
 to deliver the cellulose free. Favorable means of communica- 
 tion must therefore also be considered of first importance, 
 when selecting the place. It would consequently not be 
 economy to select a lot perhaps cheap and otherwise suitable 
 but lying off the roads. 
 
 Another important condition is abundance of pure water. 
 If the purity is not satisfactory, or at times turbulance is 
 caused by rain, etc., there from the very beginning, the plan- 
 ning of large clearing ponds or other arrangements must be 
 cared for. Care must be taken that the clearing arrangement 
 or wells are above the plant, in regard to the direction of the 
 river, so that a contamination by the waste-waters partially 
 sinking into the soil is excluded. 
 
 When the lot is not level but somewhat hilly, this can be 
 used with advantage by putting the pyrite-ovens and the 
 towers so high that the leach can be conducted through a 
 pipe-line directly into the digesters from the leach tanks, 
 whereby a leach pump becomes unnecessary. By the higher 
 situation of the towers sulphurous acid escaping on top enters 
 the high layers of the air and thus, before falling down, is 
 more diluted and made harmless. 
 
 It would not be of much value to go here beyond the general 
 rules for planning a cellulose factory, and perhaps to show for 
 example in sketch one or several existing plants, as every 
 new plant must suit the local conditions and also the instruc- 
 tions of the local authorities. Besides, in every plan the pro- 
 jected size of the planned establishment and means of the 
 proprietor must be taken into consideration, and above all 
 the system, according to which the cellulose is to be made. 
 To execute the plan of a new establishment in every single 
 instance a technical expert must certainly assist. 
 
 From the standpoint of the paper manufacturers must 
 
218 THE MANUFACTURE OF CELLULOSE. 
 
 next be viewed the two large groups of the soda and sulphite- 
 cellulose, which, because in the manufacture of paper, they 
 are intended to take the place of the rags, partially or en- 
 tirely, he likes in general to compare with the cotton and 
 linen fibre because, at least in its qualities, they do in fact 
 show much similarity to them. Both linen and cotton fibres 
 are employed with equal importance, but often one can by 
 no means be substituted for the other ; where very particular 
 qualities of a paper are in question. As a rule, however, 
 the greater value must be acknowledged to the linen fibre. 
 The same with the two celluloses mentioned : the soda cellu- 
 lose is generally softer, more similar to cotton, finding em- 
 ployment for many purposes, however the sulphite-cellulose 
 has, in a measure, displaced it because it is unconditionally 
 firmer, some sorts can be bleached better and besides it is on 
 the average sold somewhat cheaper. 
 
 The cause of the difference not only of the two principal 
 groups, but also of the celluloses of the different sulphite 
 processes compared with each other, can be perceived from the 
 comparison on the next page, which, while not quite com- 
 plete, shows however, that the pressure and the temperature 
 at which the fibre has been boiled, is of great influence. 
 
 From this can be learned that especially the soda-cellulose 
 is produced with very high pressure, high temperature, but in 
 proportion short duration of boiling; that the sulphite-cellu- 
 loses are, on the average, worked with low pressure, low tem- 
 perature and shorter time of boiling, and that especially in 
 the manufacture of Mitscherlich cellulose the lowest tem- 
 perature, the lowest pressure, but the longest time for boiling 
 are employed. According to the last-mentioned method boiling 
 is consequently the most carefully done, i. e., it is evident that 
 in slowly removing the incrusting constituents, employing 
 but the most necessary degrees of heat, the proper fibre must 
 be spared most, the produced cellulose must consequently 
 possess the greatest firmness, And such is indeed the case. 
 
 The author, when a paper manufacturer, had for a long 
 time worked in most of the different sorts of cellulose and re- 
 ceived his supply of Mitscherlich cellulose from different fac- 
 tories; but in regard to firmness this product has not yet 
 been surpassed by any other system. 
 
 When comparing soda-cellulose with the cotton fibre, the 
 Mitscherlich cellulose must be put in place -of the toughest 
 linen and hemp fibre and accc rdingly the other principal sul- 
 
THE MANUFACTURE OF CELLULOSE. 
 
 219 
 
 
 
 
 cn 
 
 
 
 
 
 
 
 
 
 
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 cn 
 
 
 
 
 
 
 »* 
 
 
 
 
 o 
 
 
 
 
 
 
 rV 
 
 
 
 
 CL 
 
 
 
 
 
 
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 PO 
 
 
 
 k 
 
 
 H 
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 P 
 3 
 
 T3 > "tc] 
 
 2. " o 
 
 rr. d- g- 
 
 
 o' 
 
 a 
 
 3 
 OfQ 
 
 a 
 
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 3* 
 
 > 
 
 3 
 
 k 
 
 3* 
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 o' 
 
 
 o 
 
 a cr ^ 
 
 p 
 
 rf 
 
 
 
 H 
 
 
 
 3 
 
 3 
 
 to 
 
 •t 
 
 
 
 O 
 
 a 
 
 3* 
 
 3 
 
 
 
 
 •-I 
 
 
 • 
 
 
 
 rt> 
 
 
 
 
 
 
 
 
 
 
 >i 
 
 
 
 
 cn 
 
 
 
 
 
 
 
 
 
 
 
 
 Cn 
 
 
 Highest pressure of 
 
 
 4^ 
 
 CO 
 
 -£■ 4*. 
 
 
 Cn 
 
 On 
 
 M 
 
 On 
 
 steam in atmos- 
 
 Co 
 
 Cn 
 
 Cn 
 
 -£■ Cn ^J 
 
 0> 
 
 "vj 
 
 CO 
 
 
 
 CO 
 
 phere. 
 
 
 
 
 
 
 vO 
 
 
 
 On 
 
 
 ►-* 
 
 
 
 
 
 o 
 
 
 
 o 
 
 
 ^j 
 
 
 
 
 
 
 
 
 
 o 
 
 Highest temperature 
 
 
 
 
 
 
 
 
 
 
 
 o 
 
 
 
 
 
 
 
 o 
 
 Cn 
 
 
 
 
 
 to 
 
 o 
 
 in degrees Celsius. 
 
 Co 
 Cn 
 
 On 
 
 N 
 
 N> ** CO 
 
 
 
 
 Co 
 
 n 
 
 
 Duration of boiling 
 
 Co 
 
 00 
 
 Co 
 
 On 
 
 "vj 
 
 i-i N\ vO 
 
 o 
 
 
 
 o 
 
 ON 
 
 in hours. 
 
 Cn 
 
 
 
 
 
 
 fn 
 
 ON 
 
 
 
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 Cn 
 
 
 
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 HI 
 
 f 
 
 ^J 
 
 
 
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 ,_, 
 
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 n 
 
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 to 
 
 to 
 
 n 
 
 3* 
 
220 THE MANUFACTURE OF CELLULOSE. 
 
 phite processes, Ritter-Kellner, Graham and Fladquist would 
 represent the finer fibres of linen. The comparison is also fit- 
 ting in reality, because it cannot be denied that the Mitscher- 
 lich cellulose, with all its advantages, has however the dis- 
 advantages, to be somewhat less pure, for which reason, when 
 bleached, it cannot well be employed for the finer sorts of 
 paper, while the cellulose according to Ritter-Kellner and a 
 few other related processes great firmness is combined with 
 great purity, and in the first qualities by glaring whiteness, 
 so that it can be used with advantage for the best papers. 
 Lately Mitscherlich cellulose is also produced bleached very 
 white and faultlessly pure. 
 
 (The End.) 
 
Qeyer's 
 
 Directory 
 
 of tlhe 
 
 AM ERICAN 
 PAPER TRADE 
 
 Published Aanntually 
 
 is the most complete, desirable and compact 
 directory of the Mills ever published. 
 
 All Mills of one owner grouped together. 
 
 Information all in one place. 
 
 The Directory also contains list of Mills 
 
 arranged by States. 
 
 Selected list of all trades allied with the 
 
 paper industry. 
 
 Every Paper Dealer, Stationer and Litho= 
 
 grapher needs a copy for Reference. 
 
 PRICE $2.00. 
 
 Aedrew Geyer 
 
 PUBLISHER 
 
 3118 Broadway = New York 
 
WATER MARKS 
 
 -AND- 
 
 TRADE MARKS 
 
 As * Applied * to * Paper 
 
 This popular little help and money-saver for 
 the trade is in universal use among all handlers 
 of paper. The cost is so low and the size so 
 handy that everybody can afford to have one 
 in his pocket, or in the pigeon hole of the desk. 
 
 THERE ARE SOME 4000 TITLES IN THE 
 BOOK. SIZE 4 1-2X6 INCHES, AND IN 
 TWO STYLES OF BINDING. ... . . 
 
 Paper Cover - 35c* 
 
 Cloth Back Linen Board Sides, 50c* 
 
 Cash to accompany all orders. 
 
 ANDREW GEYER 
 
 -PUBLISHER- 
 
 3 J 8 Broadway « « New York 
 
Cheney Blgelow Wire Works 
 
 Manufacturers of 
 
 * 
 
 Fourdrinier Wires, 
 
 Cylinder Molds, 
 
 Dandy Rolls. 
 
 * 
 * 
 * 
 * 
 * 
 * 
 * 
 * 
 * 
 * 
 
 i i In i 
 
 Office Railings, 
 Window Guards, 
 Elevator Cabs and Enclosures. 
 
 SPRINGFIELD, MASS, 
 
 Established \ 842. Incorporated 1887. 
 
 iftOl 
 
JUL 5 
 
 FOR PAPER AND PULP MILL USES 
 AND ALL CLASSES OF DRIVING. 
 
 Ko$$cnaaie... Reddaway Belting t fi«« c«. 
 
 NEWARK, NEW JERSEY. 
 
 Manufacturers-^^ 
 
 CAMEL HAIR BELTING " Camel "Brand. 
 STITCHED COTTON BELTING "Sphinx" Brand. 
 LINEN FIRE HOSE. 
 
 Try Our Camel Hair Belt, OIL FINISH. 
 
 Tackson Patent Joints are the Best for all kinds of Belting. 
 
 NEVIN IRON WORKS, 
 
 LOWVILLE, N. Y. 
 
 Manufacturers of PUMPS and WOOD PULP MACHINERY.