TANNING MATERIALS 



81 



Consequently, the bark and sap are removed from logs in the forest. 

 Furthermore, the great weight of the heartwood causes a large portion 

 of the product to be shipped to Europe and this country in the form of 

 extract, rather than in the log. 



The trees after felling and the removal of bark, branches and sap wood 

 are bucked into logs of from 4 to 16 ft. in length or more and then hauled 

 by oxen to the nearest railway. They are transported in some cases, 

 several hundred miles to Buenos Aires and Montevideo, the great que- 

 bracho wood markets. Some companies have a monthly output of 

 from 500 to 1000 tons of wood. There are five factories for the con- 

 version of the wood into extract on the upper Paraguay River. Some 

 companies which cut quebracho for cross ties, selling at $1.50 to $2.50 

 apiece, have found that there is more profit in getting out wood for extract 

 or for direct export than for the local railways. The industry has devel- 

 oped so widely that the quebracho forest region has contributed an 

 important source of income to Argentine and Paraguay. 



In the process of extraction, the wood is reduced to small chips or 

 shavings and then placed into closed copper extractors with a capacity 

 of about 530 cu. ft. each. Steam is admitted and the leaching process 

 is consummated rapidly. Consequently very concentrated liquors are 

 secured. These are cooled and clarified in the dark to prevent oxidation. 

 The extract is then evaporated in vacuum pans to a rather thick con- 

 sistency until only 20 to 25 per cent of water remains. This extract on 

 cooling, becomes solid. Analysis of quebracho extract shows about 65 

 per cent of soluble tannin content, 8 per cent insoluble tannin and 7 

 per cent of non-tannins. 



The industry has assumed large proportions in the Argentine and the 

 war has greatly stimulated prices. Since the year 1900, the value of the 

 exports of logs has increased over 100 per cent up to 1913 and the 

 value of extract over 800 per cent. 



In the year 1913 the Argentine statistics show that the total export 

 of logs and extract was 463,648 metric tons. The principal countries 

 which received this material were as follows: 



