April 1907.] 



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TIMBERS. 



THE USE OF WOOD IN PAPER-MAKING. II. 



The first time, perhaps, that wood was used to any appreciable extent in 

 the manufacture of paper was when Koops published his book, in 1800 ; but at that 

 period it could not be made to compete successfully against rags. The European 

 wars had the effect of raising the price of rags at the beginning of tli3 last century, 

 so much so, that there was a law which prohibited the burial of the dead in linen 

 shrouds. Mechanical wood, or mechanical pulp, as we know it to-day, is, as I have 

 already said, produced by keeping short cut pieces of wood by hydraulic pressure 

 against the surface of a rapidly revolving stoue, and was the first form in which 

 wood was used in any considerable quantity. Mechanical wood has very little 

 feltiug power, and is ouly capable of producing a weak paper, which contains 

 practically all the ingredients of the original wood, and from the time of its dis- 

 covery up to the present it has only been used for lower class papers. It, however, 

 constitutes the great bulk by weight of our paper-making materials, as a common 

 newspaper contains upwards of four-fifths of this substance. 



CHEMICAL PULP. 



A great change took place in the manufacture of paper on the development 

 of the sulphite process. This process consists in treating chips of wood under a 

 pressure of about seven atmospheres with a solution of bi-sulphite of lime or 

 magnesia for a period of from eight hours to three days. The first patent was 

 undoubtedly taken out by Benjamin G. Tilghman, of Philadelphia, in 1867, His 

 original specification practicaly covers the various methods employed by subsequent 

 inventors. He started by boiling in lead-lined cylinders. Although an excellent 

 fibre was obtained, the engineering difficulties rendered it necessary to abandon his 

 original process. 



The preparation of wood for the chemical process is somewhat similar to 

 that employed in preparing the wood for grinding. The wood is brought from the 

 river or from the stacks in the mill yard, sawn into suitable lengths, past through 

 the barking machine, then through the knotting machine, afterwards fed into the 

 chipping machine, which at a great rate reduces the wood into small chips. It is 

 then screened, and any further knots which appear are removed, and then the wood 

 is taken along by a conveyer from the screens to the top of the digester house, and 

 fed into the digesters through the manhole at the top. I have seen, at the modern 

 chemical pulp mills, in Sweden, Norway, Finland, United States, and Canada, 

 digesters with a capacity of 15 tons dry pump, and I have heard of a mill in North 

 Sweden with a digester which will carry at one cooking 20 tons of dry pulp. 



THE PIONEERS OF CHEMICAL PULP. 



The actual date of the invention of wood pulp is more or less problematical, 

 as the evolution of wood pulp has undoubtedly extended over a very considerable 

 period, but the reference to Tilghman may be accepted as established. Some years 

 ago a very interesting correspondence appeared in Papier Zeitung, and Professor 

 F. Fittica asserted that Mitscherlich was entitled to the honour of being recog- 

 nised as the inventor of sulphite. The editor of Papier Zeitung apparently did not 

 wish to share the responsibility for that statement, and I think the editor of our 

 esteemed German contemporary was well advised in the view he took, and in the 

 course of a very intelligent correspondence, various more or less authoritative 

 people put forward the names of Ekmann, Tilghman, Rismuller, and others, and 

 various information was forthcoming regarding priority, but the consensus of 



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