﻿16 BULLETIN" 9, XJ. S. DEPARTMENT OF AGRICULTURE. 



ACACIAS FOR TANBARK. 



At the present time the chief commercial value of acacias seems to 

 be for tanbark, although even with the tanbark species there are 

 important by-products. The tanbark industry is bound to increase 

 in importance; tanners are searching farther and farther for the 

 materials they need, especially since, for the treatment of heavy, 

 high-grade leathers, no real substitutes for the best vegetable tans 

 have yet been discovered. 



Important Tanbark Species. 



All of the leading tanbark acacias are from Australia and are gen- 

 erally known as wattles. This term is of local origin. Early settlers 

 in the Australian bush made huts by weaving or wattling green 

 branches together, and since acacias were most often used the name 

 wattle has since been applied to the strong-growing species. In his 

 time Von Mueller designated only five acacias as wattles, though he 

 names many others as yielding tanbark. Dr. Maiden applies the 

 term to more than 30 species whose bark he has tested. It is evident, 

 however, that while many will yield bark worth using, when the tree is 

 cut for timber (this is true of all the more valuable timber species) only 

 A. pycnantha and the best varieties of A. decurrens justify planting for 

 tanbark alone. Acacia decurrens mollis and decurrens normalis are 

 the largest and best of the decurrens forms, and are stronger growing 

 trees than A. pycnantha, but the latter yields the richer bark. These 

 trees, then, are all that are worth serious attention for tannic acid. 

 Acacia melanoxylon, decurrens, dealbata, longifolia, and others whose 

 timber is of first importance yield tanbark only as a by-product. 



The two decurrens varieties (Acacia decurrens mollis and A. decur- 

 rens normalis) may be taken as the typical tanbark acacias. Von 

 Mueller's statement in 1882 of the value of their bark can scarcely 

 be improved upon: 



It varies in its content of tannin from 30 to 40 per cent in bark artificially dried. 

 One and one-half pounds of the bark give 1 pound of the leather, while 5 pounds of 

 English oak bark are requisite for the same result. Melbourne tanners consider a ton 

 of black wattle bark sufficient to tan 25 or 30 hides; it is best adapted for sole leather 

 and so-called "heavy" goods. , 



Acacia Pycnantha. 



Acacia pycnantha is now strongly recommended by all who have 

 studied tanbark production from this genus. The Kew Bulletin of 

 1893 especially urges the planting of A. pycnantha. Naudin says that 

 the bark of this species has been known to contain 46 per cent of 

 tannic acid, and that ordinarily it yields from 35 to 40 per cent. 

 According to Von Mueller it is " second perhaps only to Acacia 



