CHAPTER XV 

 TANS AND DYES 



The bark and other parts of trees and herbaceous plants in 

 tropical countries show a much greater tendency toward the 

 production of tannin than is the case in cold countries. This 

 fact has led to thorough search of commercial sources of tan- 

 nins, especially in tropical woods. The commercial rank which 

 different sources of tannin occupy changes somewhat from 

 year to year as the transportation facilities and other matters 

 concerned with the economics of production are altered by 

 changing circumstances. On account of the active quest for 

 suitable sources of tannin, much attention has been given 

 to the percentage of tannin found in crude substances collected 

 as sources of tannin. 



The dyestuffs of vegetable origin have undergone great fluc- 

 tuations in value and importance since they first came into large 

 industrial use. In recent years the markets of the world have 

 been flooded with cheap synthetic dyes which have had the 

 effect of greatly checking the production of natural dyestuffs. 

 None of these artificial dyes is equal in value to the natural 

 dyes and in view of the great disturbances in the dye mar- 

 ket resulting from the European War it would seem de- 

 sirable that attention be again given to renewing and extending 

 the production of such natural dyestuffs as cutch, logwood, 

 gamboge, indigo, madder, saffron, saflSower, etc. These dyes 

 are not only superior to the artificial dyes for technical pur- 

 poses, but are harmless and some of them possess medicinal 

 properties. 



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