Leach tub

from The Collaborative International Dictionary of English v.0.48

Leach \Leach\, n. [Written also {letch}.] [Cf. As. le['a]h lye,
   G. lauge. See {Lye}.]
   1. A quantity of wood ashes, through which water passes, and
      thus imbibes the alkali.
      [1913 Webster]

   2. A tub or vat for leaching ashes, bark, etc.
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   {Leach tub}, a wooden tub in which ashes are leached.
      [1913 Webster]