Turpeth

n.
  1. (Bot.) The root of Ipomœa Turpethum, a plant of Ceylon, Malabar, and Australia, formerly used in medicine as a purgative; -- sometimes called vegetable turpeth.
  2. (Chem.) A heavy yellow powder, Hg3O2SO4, which consists of a basic mercuric sulphate; -- called also turpeth mineral.