828 JOURNAL OF FORESTRY 



At the factories, the wood is either used immediately, or piled in 

 storage yards — preferably the former, for the wood is hard enough 

 to cut at the best, and when seasoned out is almost like metal. Chippers, 

 equipped with knives set on a revolving double cone-shaped wheel, 

 like those used in chestnut extract plants, except that the openings 

 are larger and on the side rather than on top, reduce the wood to small 

 chips or coarse sawdust, the logs being placed in a trough and forced 

 by a ram endwise against the knives. 



The tannin is then leached out in tall copper cells, arranged in series, 

 by a circulating stream of hot water. The "spent" or leached chips are 

 burned for fuel. The "thin liquor" is led to storage tanks, and thence 

 to vacuum pans, heated by steam coils, when it is boiled down to a 

 thick sirupy liquor, and then passes to other vacuum pans with revolv- 

 ing internal coils of steam pipes, where it is reduced to a rosin-like 

 substance, which is drawn off hot through an opening in the bottom 

 into hundred-pound sacks, where on cooling it solidifies. 



The finished product, at present quoted at about $160 per metric 

 ton, on board ship Buenos Aires, is exported to both Europe and the 

 United States, the proportion coming to United States having increased 

 very much since 1914. 



At the present rate of use, the quebracho forests will last very many 

 years, though the easily accessible forests are nearing their end. 



Both species of red quebracho are used, though so far the Santa Fe 

 type, being in the regions first opened up, has furnished the great 

 majority of the wood used. It is said to be a little the best, both in 

 tannin content and in ease of chipping. Analysis of both varieties 

 run from 20 per cent to 30 per cent tannin. 



Quebracho is also used locally in tanneries. It is sawn or ground 

 into sawdust, and used in "layering" hides in the vats, as ground bark 

 was formerly used in the States. 



Algarroba is said to contain about 12 per cent of tannin, and is used 

 on a small scale in making extract for tanning. Its very dark color 

 hurts its value. 



In northwestern Argentine, in the Provinces of Tucuman, Salta, 

 and Jujuy, which may either be considered as an extension of the 

 Chaco or a separate forest region, there is a tree called cebil (Piptadenia 

 cebil), whose bark is very rich in tannin, and is used in quite large 

 quantities in local tanneries. 



There are many other tanniferous woods and plants, but none that 

 are used on a commercial scale. 



