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CHAPTER T. 



UTILIZATION OF THE BARK OF TREES/" 



Section I. — General Account. 



With the exception of a few other employments for bark in 

 certain countries, which will he referred to at the close of this 

 chapter, the bark of trees serves principally for tanning. In 

 order that skins of animals may be utilized for boots, articles of 

 saddlery, &c., they must be subjected to a process which pre- 

 serves them from decay, and renders them more or less supple. 



There are four methods at present employed for preparing 

 leather, that termed tamiing, when substances containing tannin 

 are used for the purpose ; tawing, by means of aluminium salts ; 

 shamoying, by means of fats or oils, [and the fourth, by means of 

 compounds of chromium.— Tr.]. 



[Tanning produces ordinary leather ; tawing — kid and other 

 white leathers which may be dyed various tints — and shamoying, 

 which is the oldest process, produces wash-leather. The process by 

 means of chromates is a comparatively recent discovery, 1882, and 

 has been reported to produce leather stronger than the best bark- 

 tanned leather. — Tr.] 



Tanning is eflfected by the affinity of tannic acid for the 

 albumen and gelatine in skins, the process partaking of a 

 chemical as well as of a physical nature ; by the union of these 

 substances a firm but supple compound is produced, which is 

 insoluble in water, resists decay, and penetrates all the other 

 components of a skin, without damaging its natural structure. 



In Germany, the production of tanning materials is chiefly 

 limited to the bark of trees. Nearly all indigenous forest trees 

 contain tannic acid in their bark, young shoots, &:c., but only a 

 few yield it in sufficient quantities to be commercially utilizable. 

 These few are oaks, spruce, to some extent also larch, willow, and 



* In Pnissia, hark is coiisidt^red an article of principal forest produce. 



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