662 UTILIZATION OF BARK AND ITS CONSTITUENTS. 



Moscow Academy, the quantity of tannic acid in willows varies 

 between 8 and 12 per cent. In Russia, it has for a long time 

 been customary to use willow-bark for tanning, especially in 

 preparing that flexible, water-tight, shining upper leather, for 

 which Russia is so famous. The pleasant scent of Russian 

 leather is due to soaking it with birch oil, distilled from the 

 white bark of birch. The well known Danish glove-leather 

 is also tanned with willow-bark. In Germany, little use has 

 hitherto been made of willow-bark, probably on account of the 

 small quantity grown. 



Peelings from osiers are dried in loose heaps and used for 

 tanning, or as litter for cattle. 



Even the bark of the black alder is used for tanning, its con- 

 tents in tannin varying from 8 to 20 per cent. (Eitner, Post, 

 Councler). In spite of its high percentage in tannin, the use of 

 alder-bark is but limited ; the tanning liquid decomposes rapidly, 

 and the leather is hard and brittle, and of a dark colour. 



Of foreign barks, that of the American red oak (Quercus 

 rtibra) is so poor in tannin that it is unsuited for bark coppice. 

 The barks of Douglas-fir and hemlock-spruce are, however, 

 very rich in tannin, so that even on this account their 

 introduction to Europe is valuable. 



SECTION IX. CELLULOSE. 



Cellulose from bark, either rhitidome or bast, resembles wood- 

 cellulose in its constituents. Bast-cellulose is characterised by 

 greater durability than the other cell-formations in bark, so that 

 the bast-fibres may be separated by maceration. When they 

 occur in clusters, owing to their toughness, they may be obtained 

 almost pure by beating the bark. By twisting these bundles, 

 they make excellent binding-material (hemp, flax). Even the 

 fine fibres of the pod of the cotton-plant (Gon&ypium) consist of 

 pure cellulose. These forms of cellulose are made into paper. 



Among trees and shrubs, which contain utilisable cellulose 

 in their bark, the following East Asiatic paper-shrubs may 

 be cited: Edgeicorthia, JinHtaxom'tia, \\ r i<-kstri>inin t Daphne, 

 Skimmia, etc. The first two are cultivated like osiers, and the 

 cellulose in their bark made into paper. 



