**2.4 Tans and dyes**

A variety of vegetable tanning materials are produced in the forests. Important vegetable tanning materials are the myrobalan nuts and bark of wattle (*Acacia mearnsii*, *A. decurrens*, *A. nilotica* and *Cassia auriculata*, etc.). Other tanning materials include leaves of *Emblica officinalis* and *Anogeissus latifolia,* bark of *Cleistanthus collinus*, *fruits of Zizyphus xylocarpa*, bark of *Cassia fistula*, *Terminalia alata*, *T. arjuna*, etc. The term tannin was introduced by Seguin in the year 1796 to indicate various plant extracts, which have the capacity to convert hides and skins into leather [5, 29, 30]. Tans and dyes are simple chemical compounds made of carbon, hydrogen and oxygen. The structure and solubility of tannins are dependent upon the source and structure of tannins, however, vegetable tannins are water-soluble.
