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molecular sieve

noun, Chemistry
1.
a compound with molecule-size pores, as some sodium aluminum silicates, that chemically locks molecules in them: used in purification and separation processes.
Origin
1925-1930
1925-30
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Based on the Random House Dictionary, © Random House, Inc. 2014.
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British Dictionary definitions for molecular-sieve

molecular sieve

noun
1.
(chem) a material that can absorb large amounts of certain compounds while not absorbing others and is thus suitable for use in separating mixtures
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Encyclopedia Article for molecular-sieve

molecular sieve

a porous solid, usually a synthetic or a natural zeolite, that separates particles of molecular dimension. Zeolites are hydrated metal aluminosilicate compounds with well-defined crystalline structures. The silicate and aluminate groupings form three-dimensional crystal lattices surrounding cavities in which the metal ions and the water molecules are loosely held. Channels run through the entire crystal, interconnecting the cavities and terminating at the crystal surface. Upon heating, the zeolites lose their water content with little or no change in their crystal structure. The dehydrated zeolite can reversibly absorb water or other molecules that are small enough to pass through the channels or pores. The metal ions are also readily replaceable by other ionic units of similar charge and size

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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