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A molecular sieve is a material with pores (voids or holes), having uniform size comparable to that of individual molecules, linking the interior of the solid to its exterior. These materials embody the molecular sieve effect, the preferential sieving of molecules larger than the pores.
Size-exclusion chromatography, also known as molecular sieve chromatography, [1] is a chromatographic method in which molecules in solution are separated by their shape, and in some cases size. [2] It is usually applied to large molecules or macromolecular complexes such as proteins and industrial polymers . [ 3 ]
It operates at near-ambient temperature and significantly differs from the cryogenic distillation commonly used to separate gases. Selective adsorbent materials (e.g., zeolites, (aka molecular sieves), activated carbon, etc.) are used as trapping material, preferentially adsorbing the target gas species at high pressure. The process then swings ...
Canisters are commonly filled with silica gel and other molecular sieves as desiccants in drug containers to keep contents dry Silica gel in a sachet or porous packet. A desiccant is a hygroscopic substance that is used to induce or sustain a state of dryness (desiccation) in its vicinity; it is the opposite of a humectant.
The typical molecular sieve used is a synthetic zeolite with a pore diameter around 0.4 nanometer ( Type 4A ) and a surface area of about 500 m 2 /g. The sorption pump contains between 300 g and 1.2 kg of molecular sieve. A 15-liter system will be pumped down to about 10 −2 mbar by 300 g molecular sieve. [1]
This Wikipedia page provides a comprehensive list of boiling and freezing points for various solvents.
Another form of electronic dry box technology utilizes multi-porous molecular sieve desiccants to absorb moisture. This moisture and humidity control technology is renewable without having to replace desiccant and is capable of reaching low humidity (20%RH or less) to ultra low humidity (5%RH or less) levels.
Molecular distillation is vacuum distillation below the pressure of 0.01 torr. 0.01 torr is one order of magnitude above high vacuum, where fluids are in the free molecular flow regime, i.e., the mean free path of molecules is comparable to the size of the equipment. The gaseous phase no longer exerts significant pressure on the substance to be ...