Molecular Sieve is a material that contains precise and single tiny holes that can be used to adsorb gases or liquids. Small enough molecules can be adsorbed through the pore, while larger molecules can not. The difference with a normal sieve is that it operates at the molecular level. For example, a molecule of water that is small enough to pass but a little larger than it does not. Therefore, molecular sieve commonly used as a desiccant. A molecular sieve can absorb up to 22% of its own weight of water. Molecular sieves are often used in the petroleum industry, especially for purification of gases. For example, silica gel can be used to adsorb mercury from natural gas to corrode aluminum pipes and other liquefaction equipment.