The New Student's Reference Work/Tannin
Tan′nin or Tan′nic Ac′id is of great importance in tanning leather. The chief source of tannin is oak-bark, though in America hemlock-bark is much used, while the mimosa or wattle-barks of Australia are important. However, tannin is found in the bark and leaves of most forest-trees, as the elm, willow, horse-chestnut, and pine, and in many fruit-trees as the pear and plum. Coffee, tea and, especially, Paraguay tea also contain tannin.