SCIENCE IN THE INDUSTRIAL WORLD 



to the difficulty of procuring the necessary apparatus. 

 The strong chemicals employed penetrated the linings 

 of the digestors as then constructed, eating into their 

 shells and rapidly spoiling them for use; and until 

 recently no species of lining has been found to resist 

 the attacks of the acid and keep the digestors whole. 

 Within a few years, however, linings have been in- 

 vented which secure this end, and the sulphite process 

 is now established as the leading method of securing 

 chemical pulp. 



" Soda fiber is ordinarily made from woods softer than 

 spruce, chiefly poplar, and is a softer, mellower fiber, 

 without much strength. It is used as a soft stock 

 in book, and to some extent in writing-papers. Its 

 preparation is similar to that of sulphite, except that 

 in place of sulphurous acid a solution of caustic soda 

 is used in the digestors. The process is older than 

 either of the two just mentioned, having been intro- 

 duced into this country from England in 1854. It 

 came into extended use earlier than the sulphite fiber, 

 but owing to the greater cheapness of the sulphite 

 process in producing a strong cellulose fiber from 

 spruce, the use of the latter has increased more rapidly 

 than that of soda. 



"The merchantable shape of these fibers differs some- 

 what. Ground wood is ordinarily sold in folded sheets 

 only partially dry, and is, therefore, under common con- 

 ditions only suitable for use near the locality of its 

 manufacture, its weight being so increased by the water 

 as to preclude the profitable transportation of such a 

 low-priced product, on account of the freight on this 



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