Also leech, latch, letch. [Prob. repr. OE. lęccan to water (trans. L. rigare):—WGer. type *lakkjan:—*lakjan, f. *lak-: see LAKE sb.3 There appears to be no trace of the vb. between OE. and the examples of the technological use in the 18th c., exc. the doubtful instance in Shaks. and one other (see 1, 2 below). The form letch is normal; the variant leach is phonologically obscure.]
† 1. trans. To water, wet. Obs. rare.
(In the Shaks. quot. the vb. may possibly belong to LATCH v.2, in the transferred sense ‘to fasten.’)
c. 888. K. Ælfred, Boeth., xxxix. 13 (Sedgefield), 136/17. Hæʓlas & snawas & se oftræda ren leccað þa eorðan on wintra.
1590. Shaks., Mids. N., III. ii. 36 (1st Qo.). But hast thou yet latcht [2nd Qo. & 1st Fol. lacht] the Athenians eyes, With the loue iuice, as I did bid thee doe?
† 2. intr. To soften, melt. Obs.
1614. H. Greenwood, Jayle Deliv., 470. Merchants wax must leach in a candle, before it can take a stampe or impression.
3. a. trans. To cause (a liquid) to percolate through some material.
1796. Morse, Amer. Geog., I. 439. Cider … is first separated from the filth and dregs, either by leaching through sand, or straining it through flannel cloths.
1828–32. Webster, Leach, to wash, as ashes, by percolation, or causing water to pass through them, and thus to separate from them the alkali. The water thus charged with alkali is called lye.
b. To subject (bark, ores, etc.) to the action of percolating water, etc., with the view of removing the soluble constituents; to lixiviate.
1877. Raymond, Statist. Mines & Mining, 403. Concentrated liquid obtained by leaching the ores in this process, at Widnes, in England.
1882. J. Paton, in Encycl. Brit., XIV. 382/2. The tanning materials so prepared are next leached, latched, or infused for preparing the strongest tanning solutions.
1882. Rep. to Ho. Repr. Prec. Met. U.S., 112. Chlorination works are needed for leaching the sulphurets.
1885. H. M. Newhall in Harper’s Mag., Jan., 276/1. Most tanners … grind it [bark] in a bark mill, ‘leaching’ the bark to obtain the liquor.
c. intr. To pass through by percolation (Webster, 1864). Also intr. for refl. Of ashes: To be subject to the action of percolating water.
1883. Ellen H. Rollins (‘E. H. Arr’), New Eng. Bygones, 68. The ashes of those ancient wood-fires … went to leach in the spring for the making of family soap.
4. trans. To take away, out, by percolation.
1860. Maury, Phys. Geog. Sea., i. 16. The tides … leached out of the disintegrated materials … every soluble ingredient known in nature.
1877. N. S. Shaler, App. to J. A. Allen’s Amer. Bison, 458. Whenever the rocks lie above the line of the drainage, these salts have been leached away.
1884. Engineer, 12 Sept., 239/3. After leaching out the chloride the tails may be treated.
1900. Nature, 19 July, 277/2. A moist climate would tend to leach the calcareous matter from the rock.
Hence Leached ppl. a.
1862. Marsh, Eng. Lang., 40. A melancholy heap of leached ashes, marrowless bones, and empty oyster-shells.
1895. Offic. Mining Rep. N. Zealand, 10. Separating the cyanide solutions from the leached pulp.
