552 AUXILIARY FOREST INDUSTRIES. 



than for small pieces. The wood should be free from knots 

 and perfectly sound ; half dead and dead wood from thinnings 

 is rejected. Peeled round pieces 10 to 30 cm. in diameter 

 and 2 to 4 m. long are stacked in cords for pulp-wood. 



The present enormous demand for wood-pulp is one of the 

 chief causes of the clearance of numerous private woodlands, 

 as wood of moderate dimensions is quite suitable. In Saxony 

 60% of the total timber-supply was used in 1902 for paper- 

 pulp. In North America (19003) 200,000 acres of forest 

 were cleared for wood-pulp, in order to supply 210 paper 

 factories. By far the greatest supply of paper-pulp comes 

 npw from the extensive coniferous forests of Canada, and is 

 more and more threatening to German trade. 



As has been explained on p. 79, the walls of wood-fibres 

 are formed chiefly of cellulose and lignin, with gum, tannin, 

 coniform, etc. In order to separate the cellulose from these 

 substances, the wood is macerated and the lignin, gums, etc., 

 separated as " incr Listing material " from the pure cellulose. 

 Various acids, such as nitric acid and mixtures of nitric and 

 hydrochloric acid are used ; but independently of the great 

 uost of these acids for they can be employed only once this 

 combination with cellulose is caustic and emits poisonous 



The treatment with nitric acid attacks the cellulose and 

 converts it into sugar, which may be neutralised with lime 

 and made into alcohol. At Bex,* in Switzerland, 1 cubic meter 

 (35 cubic feet) of silver-fir wood yields 100 kilos (220 Ibs.) 

 of unbleached and 70 kilos of bleached cellulose. 



Caustic alkalis also dissolve the incrusting substances and 

 saponify the resin ; they have the great advantage of being 

 utilisable several times for maceration. Of these alkalis 

 caustic soda is the most important ; it is prepared from soda 

 by the addition of lime. 



In preparing cellulose by means of caustic soda, the wood, 

 freed from bark, knots, etc., is cut in an oblique direction to 

 its length into pieces about 2 cm. thick ; they are ground into 

 splinters between fluted rollers, working as in a large coffee- 

 grinder, that are 2 cm. long and 5 and 8 mm. thick. These 



* JJrrsdi. ' Die \'c;r\v<Tt 111114- <les I Inl/.cs mil' duMnisclit'ii Wrijr 



