S: UMN – http://www.d.umn.edu/~ssternbe/Courses/LabII/exleach.pdf (last access: 15 December 2012); EncBrit – http://global.britannica.com/science/leaching-geochemistry-of-soil (last access: 30 July 2015).
N: 1. Old English leccan “to moisten, water, wet, irrigate”. The word disappears, then re-emerges late 18c. In a technological sense in reference to percolating liquids. Related: Leached; leaching.
2. The leaching of a substance from a solid material with the aid of a liquid is a common process in chemical engineering, especially where biological materials are concerned. A familiar operation which illustrates the process very clearly is the making of tea or coffee, where hot water is used to perform the extraction from tea leaves or coffee beans. Other examples are the extraction of sugar from sugar beets and oils from seeds. Extractions can be made with either water or organic solvents, at various temperatures and with different solvent flow arrangements.
3. It is important in the chemical industry to be able to make an estimate of the extent of leaching which can be obtained for a given procedure, i.e., to calculate the amount of soluble substance leached from a solid, knowing the initial solute content of the solid, the number and amount of washings with leaching solvent, the concentration of solute in the leaching solvent, if any, and the method, whether batch or continuous countercurrent. Alternatively, it may be necessary to compute the number of washings, or number of stages, required to reduce the solute content of the solid to some specified value, knowing the amount and solute concentration of the leaching solvent. The methods of calculation are very similar to those used for liquid extraction.
S: 1. OED – http://www.etymonline.com/index.php?allowed_in_frame=0&search=leaching&searchmode=none (last access: 15 December 2013). 2 & 3. UMN – http://www.d.umn.edu/~ssternbe/Courses/LabII/exleach.pdf (last access 15 December 2012).
S: GDT; TERMIUMPLUS.