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  • silica gel
  • Silica gel is a granular, vitreous, porous form of silicon dioxide made synthetically from sodium silicate. (wikipedia.org)
  • Silica gel contains a nano-porous silica micro-structure, suspended inside a liquid. (wikipedia.org)
  • Most applications of silica gel require it to be dried, in which case it is called silica xerogel. (wikipedia.org)
  • For practical purposes, silica gel is often interchangeable with silica xerogel. (wikipedia.org)
  • Silica gel is most commonly encountered in everyday life as beads in a small (typically 2 x 3 cm) paper packet. (wikipedia.org)
  • Since such packets may resemble sachets of sugar or salt and because silica gel may have added toxic chemical indicators (see below), silica gel packets usually bear warnings for the user not to eat the contents. (wikipedia.org)
  • Silica gel was in existence as early as the 1640s as a scientific curiosity. (wikipedia.org)
  • citation needed] The synthetic route for producing silica gel was patented by chemistry professor Walter A. Patrick at Johns Hopkins University in 1918. (wikipedia.org)
  • In World War II, silica gel was indispensable in the war effort for keeping penicillin dry, protecting military equipment from moisture damage[citation needed], as a fluid cracking catalyst for the production of high octane gasoline, and as a catalyst support for the manufacture of butadiene from ethanol, feedstock for the synthetic rubber program. (wikipedia.org)
  • Type C - translucent, micro-pored structure, raw material for preparation of silica gel cat litter. (wikipedia.org)
  • Additionally dried and screened, it forms macro-pored silica gel which is used as drier, adsorbent and catalyst carrier. (wikipedia.org)
  • Superficial polarity, thermal stability, performance greater than fine-pored silica gel. (wikipedia.org)
  • Stabilizing silica gel - non-crystalline micro-porous solid powder, nontoxic, flame-resisting, used in brewery of grains for beer to improve taste, clearness, color and foam, removal of non-micro-organism impurities. (wikipedia.org)
  • Silica gel is often described as "absorbing" moisture, which may be appropriate when the gel's microscopic structure is ignored, as in silica gel packs or other products. (wikipedia.org)
  • Some types of silica gel will "pop" when exposed to enough water. (wikipedia.org)
  • An aqueous solution of sodium silicate is acidified to produce a gelatinous precipitate that is washed, then dehydrated to produce colorless silica gel. (wikipedia.org)
  • When a visible indication of the moisture content of the silica gel is required, ammonium tetrachlorocobaltate(II) (NH4)2CoCl4 or cobalt chloride CoCl2 is added. (wikipedia.org)
  • Due to the connection between cancer and cobalt chloride, it has been forbidden in Europe on silica gel. (wikipedia.org)
  • Through the inclusion of silica gel packets, these items can be preserved longer. (wikipedia.org)
  • Silica gel may also be used to keep the relative humidity (RH) inside a high frequency radio or satellite transmission system waveguide as low as possible (see also Humidity buffering). (wikipedia.org)
  • It is common for a small compressed air system (similar to a small home aquarium pump) to be employed to circulate the air inside the waveguide over a jar of silica gel. (wikipedia.org)
  • The most common stationary phase for column chromatography is silica gel, the next most common being alumina. (wikipedia.org)
  • For example, one of the most widely used silica gel grades in the former technique is mesh 230 - 400 (40 - 63 µm), while the latter technique typically requires mesh 70 - 230 (63 - 200 µm) silica gel. (wikipedia.org)
  • The van URK-Salkowski reagent - a sensitive and specific chromogenic reagent for silica gel thin-layer chromatographic detection and identification of indole derivatives" (PDF). (wikipedia.org)
  • agarose
  • Agarose is available as a white powder which dissolves in near-boiling water, and forms a gel when it cools. (wikipedia.org)
  • Agarose exhibits the phenomenon of thermal hysteresis in its liquid-to-gel transition, i.e. it gels and melts at different temperatures. (wikipedia.org)
  • The gelling and melting temperatures vary depending on the type of agarose. (wikipedia.org)
  • The gelling and melting temperatures are therefore given at a specified agarose concentration. (wikipedia.org)
  • Natural agarose contains uncharged methyl groups and the extent of methylation is directly proportional to the gelling temperature. (wikipedia.org)
  • The agarose in the gel forms a meshwork that contains pores, and the size of the pores depends on the concentration of agarose added. (wikipedia.org)
  • On standing the agarose gels are prone to syneresis (extrusion of water through the gel surface), but the process is slow enough to not interfere with the use of the gel. (wikipedia.org)
  • The melting and gelling temperatures of agarose can be modified by chemical modifications, most commonly by hydroxyethylation, which reduces the number of intrastrand hydrogen bonds, resulting in lower melting and setting temperatures than standard agaroses. (wikipedia.org)
  • sedimentation
  • If the particles are large enough, then their dynamic behavior in any given period of time in suspension would be governed by forces of gravity and sedimentation. (wikipedia.org)
  • buffer
  • Desalting and buffer exchange are two of the most common gel filtration chromatography applications, and they can be performed using the same resin. (wikipedia.org)
  • The macromolecular components are recovered in the buffer used to pre-equilibrate the gel-filtration matrix, while the small molecules can be collected in a later fraction volume or be left trapped in the resin. (wikipedia.org)
  • Dialysis is useful for many of the same desalting and buffer exchange applications performed with gel filtration chromatography, as both methods are based on similar molecular weight cut-off limits. (wikipedia.org)
  • Sealed chromatography cartridges or columns work similarly except the sample and buffer is pumped into and through the resin by an external device such as a liquid chromatographic (LC) system, also requiring collection and monitoring of several fractions. (wikipedia.org)
  • form
  • These methods are based on gel filtration chromatography, also called molecular sieve chromatography, which is a form of size-exclusion chromatography. (wikipedia.org)
  • The interest in sol-gel processing can be traced back in the mid-1800s with the observation that the hydrolysis of tetraethyl orthosilicate (TEOS) under acidic conditions led to the formation of SiO2 in the form of fibers and monoliths. (wikipedia.org)
  • The positively charged Tris ions migrate through the gel to the cathode where they neutralise hydroxide ions to form Tris molecules and water. (wikipedia.org)
  • liquid
  • In this chemical procedure, the "sol" (or solution) gradually evolves towards the formation of a gel-like diphasic system containing both a liquid phase and solid phase whose morphologies range from discrete particles to continuous polymer networks. (wikipedia.org)
  • In this process, the sol (or solution) evolves gradually towards the formation of a gel-like network containing both a liquid phase and a solid phase. (wikipedia.org)
  • In countercurrent chromatography centrifugal or gravitational forces immobilize the stationary liquid layer. (wikipedia.org)
  • They are commonly used in liquid or gel minipump dispenser spigots, spray devices, some rubber bulbs for pumping air, etc., manual air pumps and some other pumps, and refillable dispensing syringes. (wikipedia.org)
  • mixture
  • The "improved hallucinogen reagent", which uses 5% DMAB in 1:1 concentrated phosphoric acid (specific gravity 1.75) / methanol mixture. (wikipedia.org)
  • process
  • During the entire chromatography process the eluent is collected in a series of fractions. (wikipedia.org)
  • The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. (wikipedia.org)
  • Sol-gel research grew to be so important that in the 1990s more than 35,000 papers were published worldwide on the process. (wikipedia.org)
  • The sol-gel process is a wet-chemical technique used for the fabrication of both glassy and ceramic materials. (wikipedia.org)
  • technique
  • The sol-gel approach is a cheap and low-temperature technique that allows the fine control of the product's chemical composition. (wikipedia.org)
  • particles
  • In the case of the colloid, the volume fraction of particles (or particle density) may be so low that a significant amount of fluid may need to be removed initially for the gel-like properties to be recognized. (wikipedia.org)
  • advantage
  • Gel filtration has the advantage of speed (a few minutes vs. hours for dialysis), though, along with the ability to remove contaminants from relatively small-volume samples compared to dialysis, an important feature when working with toxic or radioactive substances. (wikipedia.org)
  • interest
  • It is chosen so that the retention factor value of the compound of interest is roughly around 0.2 - 0.3 in order to minimize the time and the amount of eluent to run the chromatography. (wikipedia.org)
  • water
  • Once saturated with water, the gel can be regenerated by heating it to 120 °C (250 °F) for 1-2 hours. (wikipedia.org)
  • Particles
  • The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network (or gel) of either discrete particles or network polymers. (wikipedia.org)
  • In the case of the colloid, the volume fraction of particles (or particle density) may be so low that a significant amount of fluid may need to be removed initially for the gel-like properties to be recognized. (wikipedia.org)
  • If the particles are large enough, then their dynamic behavior in any given period of time in suspension would be governed by forces of gravity and sedimentation. (wikipedia.org)
  • solvents
  • Also, gel filtration is compatible with organic and other solvents that dissolve or otherwise compromise the integrity of dialysis membranes. (thermofisher.com)
  • micro-porous
  • Stabilizing silica gel - non-crystalline micro-porous solid powder, nontoxic, flame-resisting, used in brewery of grains for beer to improve taste, clearness, color and foam, removal of non-micro-organism impurities. (wikipedia.org)
  • buffer exchange
  • In desalting and buffer exchange, the macromolecular components of a sample are recovered in the buffer used to pre-equilibrate the gel-filtration matrix through which the sample is processed. (thermofisher.com)
  • high
  • Silica gel may also be used to keep the relative humidity (RH) inside a high frequency radio or satellite transmission system waveguide as low as possible (see also Humidity buffering). (wikipedia.org)