ECONOMIC USES 301 



ECONOMIC USES OF TANNINS. 



A great variety of tannins are commercially exploited and 

 it is proposed here to mention only a few representative ex- 

 amples classified according to their sources of origin : — 



I. Tannins derived from leaves and young twigs : — 

 Sumach from leaves of Rhus coriaria, and 

 Gambir from leaves of Uncaria Gambir. 



II. Tannins derived from galls : — 



Aleppo or Turkey galls — Quercus infectoria and other 



species 

 Chinese galls — Rhus semialata. 



III. Tannins derived from barks : — 



Oak-bark tannin from Quercus sessiliflora, Q. pedunculata, 



Q. cerris. 

 Tannins from bark of Salix, Betula, Picea excelsa, 



Acacia, Mimosa, Eucalyptus, Mangrove. 

 Quebracho from bark of Rhizophora. 

 Kino from bark of Pterocarpus. 



IV. Tannins from wood :• — 

 Chestnut and oak. 

 Bengal or acacia catechu. 



V. Tannins from roots : — 



Canaigre from root of Rumex hymenosepalus. 

 Tannins from roots of Geum rivale and Potentilla tormen- 

 tilla. 



VI. Tannins from fruits : — 

 Myrobalans from Terminalia. 

 Divi-divi from Ccesalpinia coriaria. 

 Valonia from Quercus csgilops and Q. cocci/era. 



These tannins are used for a variety of purposes. The 

 tannins from galls are employed chiefly for the production of 

 inks, only some of them being suitable for leather manufacture. 



Oak-bark tannin is particularly adapted for the production 

 of leather.* While oak bark itself is used directly for tanning, 

 oak wood is never so used, only extracts of the wood being 



* See Procter : " The Making of Leather," Cambridge, 1914- 



