leach

Meanings

1. 1
   verb

   to remove soluble substances from a material by passing liquid through it

   Heavy rain can leach nitrogen from sandy soil.

2. 2
   verb

   of a dissolved substance: to seep or drain gradually through soil or another porous material

   Toxic metals may leach into the groundwater after a flood.

3. 3
   noun

   a bed, vat, or quantity of material through which liquid is passed to extract soluble substances

   The workers poured water through the ash leach to produce an alkaline solution.

The verb's origin is uncertain. It is probably related to older leach or letch, a perforated vessel for extracting lye from ashes, and ultimately to Germanic words for wetting, leaking, and draining. The chemical sense preserves liquid passing through material; Walden's 'leach hole' applies that seepage idea to a supposed pond outlet.

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