File Silica gel bag open with beads.jpg thumb Silica gel A desiccant is a hygroscopic substance that induces ... of water molecules. Pre packaged desiccant is most commonly used to remove excessive humidity ... of table salt for effective pouring or shaking. Rice, however, is not a good general purpose desiccant ... effective desiccant, used for millennia in preparation of dried food and also to mummy mummify corpses. A specific usage of a desiccant would be in Insulated glazing insulated windows where it is placed ... between the panes. Toxicity A desiccant may be chosen for a particular task based not only on its ... foods. Chemical reactivity Because of their common use in preservation, it is usually desirable for a desiccant ... based desiccants. Performance efficiency One measure of desiccant efficiency is the ratio or percentage of water storable in the desiccant, relative to the mass of desiccant. Another measure is the residual relative humidity of the air or other fluid being dried. The performance of any desiccant varies with temperature and both relative humidity and absolute humidity . To some extent, desiccant performance can be precisely described, but most commonly, the final choice of which desiccant ... Silica Gel Often some sort of humidity indicator is included in the desiccant to show, by color changes, the degree of water saturation of the desiccant. One commonly used indicator is Cobalt ... Law Analysis of Desiccant Cooling Systems journal Journal of Solar Energy Engineering volume 104 ... links http www.absorcare.net desiccantDesiccant Science and Tehnology Published Paper http foodsave.net controlled atmosphere requiremen.htm Desiccant Requirement Chart printable http www.qiaoyun.net desiccant desiccant.htm Latest US desiccants patents information. http www.agmcontainer.com desiccantcity desiccant calculator.php A Desiccant Requirements Calculator http www.naturalproductsinsider.com ... page.php?id 641 Liquid Desiccant Waterfall for attractive building dehumidification cite web publisher ... more details
The term drying agent has different meanings Desiccant for materials that absorb moisture and water Oil drying agent s for compounds that speed up the drying oil hardening of oils , often used in painting disambig ... more details
Unreferenced date October 2006 Image chem drying tubes.jpg thumb right 250px A variety of empty glass drying tubes. When used, they are packed with a desiccant, usually calcium chloride. A drying tube or guard tube is a tube like piece of apparatus used to house a disposable solid desiccant , wherein at one end the tube like structure terminates in a ground glass joint for use in connecting the drying tube to a reaction vessel, for the purpose of keeping that reaction vessel free of moisture. The tube like structure is often bent and can also widen to form a bulb desiccant reservoir. Typically a drying tube is 1 2 cm wide and 5 10 cm long and bent at an angle of about 90 degrees. In use, the drying tube is filled with a rechargeable desiccant such as calcium chloride , and the open end of drying tube is partially blocked e.g. with wool, glasswool or a bung cork which has a small bore made in it and the drying tube is connected to the apparatus to be kept dry via the ground glass joint. If the drying tube is bent the bend is oriented so that solid desiccant does not fall into the reaction vessel. Some drying tubes have a glass sinter to prevent desiccant falling into the reaction vessel. Drying tubes are often prepared in advance and the desiccant can be replaced when exhausted. Reactions which are being heated, or which evolve gases, must never be sealed because an overpressure may shatter the vessel. Drying tubes are usually fitted on top of the reflux condenser laboratory condenser , allowing the pressure to be relieved while excluding atmospheric moisture. Drying tubes are often used in less demanding applications, typically in organic syntheses . One good example is the Fultz reaction . While the reaction is often carried out at room temperature, the solvent, usually volatile diethyl ether or tetrahydrofuran is already able to displace air directly, making additional measures to exclude atmospheric moisture less important. An oil bubbler may be a usefu ... more details
A desiccant is a substance that absorbs water. It is most commonly used to remove humidity that would normally degrade or even destroy products sensitive to moisture. see also desiccant List of desiccants Activated alumina Aerogel Benzophenone Bentonite Bentonite clay Calcium chloride Calcium hydride Calcium sulfate Cobalt II chloride Copper II sulfate Lithium chloride Lithium hydride Lithium bromide Magnesium Magnesium sulfate Magnesium perchlorate Molecular sieve NaK , a sodium potassium alloy Phosphorus pentoxide Potassium Potassium carbonate Silica gel Sodium Sodium chlorate Sodium chloride Sodium hydroxide Sodium sulfate Sodium benzophenone Sucrose Sulfuric Acid External links http www.mallbaker.com techlib documents americas 3045.html Desiccant Selection Guide http www.merck chemicals.com is bin INTERSHOP.enfinity WFS Merck International Site en US USD ViewProductDetail Attachments?ProductUUID 0Y.b.s1ORWYAAAEWCLMW4z8f&PortalCatalogUUID Uc6b.s1LfzAAAAEW6tYfVhTl&SelectedDocumentType Bro ankerBrochures Drying agents brochure from Merck http www.sud chemie.com scmcms web content.jsp?nodeId 3944&lang en Education Center Category Desiccants Category Chemistry lists Desiccants pt Anexo Lista de dessecantes nl Lijst van droogmiddelen ... more details
Cleanup date August 2010 A humidity indicator is a moisture sensitive chemical that changes color when the indicated relative humidity is exceeded. Some chemicals are cobalt II chloride toxic blue to pink copper II chloride yellow to blue There are other colors like Orange colour orange See also Moisture analysis Humidity indicator card Desiccant http www.healthocrates.com Chemical Sensitive Chemical Sensitive Chem stub DEFAULTSORT Humidity Indicator Category Desiccation ... more details
primarysources date May 2009 File Drierite indicateur cropped.jpg thumb Left dry Right moist Drierite is the brand name and registered trademark for a variety of desiccant s made from calcium sulfate gypsum . Some varieties contain a moisture sensitive color indicator that shows when that material s activity has been depleted. Drierite is manufactured in the USA by the W.A. Hammond Drierite Co., Ltd., founded by William Archie Hammond and headquartered in Xenia, Ohio . ref name WAHammond cite web url http drierite.com default.cfm title Drierite Desiccants accessdate 2009 05 08 ref References reflist Category Laboratory equipment Category Desiccants fr Drierite ... more details
Orphan date February 2009 In pharmacology , diapalma from Latin Lat dia , made of palma , palm ref name OED OED diapalma ref is a desiccant desiccating or drying plaster , named for the wood of the palm tree , from which the spatula is made that is used to stir the mixture while boiling. ref name cycl 1728 ref It was formerly composed of common oil, hogs fat, and litharge of gold ref name cycl or also of palm oil , litharge, and zinc sulfate . Now, it is made of white wax, emplastrum simplex, and sulfate of zinc. ref name OED References references Category Desiccants pharma stub ... more details
for dry boxes and cabinets dry box image Desiccator.jpg thumb right A desiccator right and a vacuum desiccator left note the stopcock which allows a vacuum to be applied. The blue silica gel in the space below the platform is used as the desiccant . Desiccators are sealable enclosures containing desiccant s used for preserving moisture sensitive items. A common use for desiccators is to protect chemicals which are hygroscopic or which react with water from humidity . The contents of desiccators are exposed to atmospheric moisture whenever the desiccators are opened. It also requires some time to achieve a low humidity. Hence they are not appropriate for storing chemicals which react quickly or violently with atmospheric moisture such as the alkali metals. A glovebox or Schlenk line Schlenk type apparatus may be more suitable for these purposes. Desiccators are sometimes used to remove traces of water from an almost dry sample. Where a desiccator alone is unsatisfactory, the sample may be dried at elevated temperature using Abderhalden s drying pistol . Operation In laboratory use, the most common desiccators are circular, and made of heavy glass . There is usually a removable platform on which the items to be stored are placed. The desiccant, usually an otherwise inert solid such as silica gel , fills the space under the platform. A stopcock may be included to permit the desiccator to be evacuated. Such models are usually known as vacuum desiccators . When a vacuum is to be applied, it is a common practice to criss cross the vacuum desiccator with tape, or to place it behind a screen to minimize damage or injury caused by an Implosion mechanical process implosion . To maintain a good seal, vacuum grease lubricant grease is usually applied to the flange s. See also Desiccation References citations missing date October 2009 Category laboratory glassware ar ca Dessecador cs Exsik tor da Ekssikator de Exsikkator Chemie es Desecador fa fr Dessiccateur verr ... more details
for the chambers used in chemistry Desiccator A dry box is a storage container in which the interior is kept at a low level of humidity. Dry boxes are used to safely store items which would otherwise be damaged or adversely affected by excessive humidity , such as Camera cameras and Camera lens lenses to prevent fungal growth , and musical instruments to prevent humidity induced swelling or shrinkage of wooden instrument parts . They are also used in the storage of surface mount electronic components prior to circuit board assembly. Types Desiccant boxes A simple dry box can consist of nothing more than a sealed, airtight box containing a desiccant such as silica gel or anhydrous calcium chloride. These can be easily built at relatively low cost. However, the humidity level in such boxes cannot be controlled or regulated owing to the difficulty of gauging the quantity of desiccant required to achieve a certain humidity level. Electronic dry boxes Electronic dry boxes contain a small Thermoelectric cooling peltier cooler , which remove moisture from the air by condensing it out. A control dial is usually provided which permits the user rough adjustment of the humidity level. More sophisticated designs link the cooler to a settable digital hygrometer, allowing very precise humidity level control. References references http www.drycabinets.com DryCabinets.com http www.2spi.com catalog boxes basic glove.shtml http www.2spi.com catalog boxes nitro box.shtml Category Tools tool stub ... more details
missing date October 2009 External links http www.agmcontainer.com desiccantcity desiccant calculator.php A Desiccant Requirements Calculator Category Broadcast engineering Category Chemical ... more details
Refimprove date December 2008 Activated alumina is manufactured from aluminium hydroxide by dehydroxylating it in a way that produces a highly porous material this material can have a surface area significantly over 200 square metres g. The compound is used as a desiccant to keep things dry by absorbing water from the air and as a filter water filter of fluoride , arsenic and selenium in drinking water . It is made of aluminium oxide alumina Al sub 2 sub O sub 3 sub , the same chemical substance as sapphire and rubies but without the impurities that give those gems their color . It has a very high surface area to weight ratio. That means it has a lot of very small pores, almost like tunnels, that run throughout it. Uses Catalyst applications Activated alumina is used for a wide range of adsorbent and catalyst applications including the adsorption of catalysts in polyethylene production, in hydrogen peroxide production, as a selective adsorbent for many chemicals including arsenic , fluoride , in sulfur removal from gas streams Claus Catalyst process . Desiccant Use as a desiccant, it works by a process called adsorption . The water in the air actually sticks to the alumina itself in between the tiny passages, as the air passes through them. The water molecules become trapped so that the air is dried out as it passes through the filter. This process is reversible, and if the alumina desiccant is heated to about 200 C it will release all of the water stored in it. This process is called regenerating the desiccant. Air always has some water in it one way to measure the amount of water in the air is the air s dew point . Fluoride adsorbent Activated alumina is also widely used to remove fluoride from drinking water. In the US, there are widespread water fluoridation programs to fluoridate drinking water. However, in certain regions, such as the Jaipur region of India, there is enough fluorine in the water to cause fluorosis . Activated alumina filters can easily reduce ... more details
Wiktionarypar dryer drier A dryer or drier most commonly means Hair dryer Hand dryer Clothes dryer , also known as a tumble dryer Cereal dryer , for food preservation Desiccant , a substance that absorbs or adsorbs water Grain dryer for storage grain bin s Oil drying agent , an additive which accelerates the film formation of a drying oil People Fred Dryer , American pro football player and actor Ivan Dryer , Designer of laser light shows Moosie Drier , American actor Sally Dryer , American voice actress from the 1960s Thomas J. Dryer , 19th century American newspaper publisher See also Dreier Drying disambig ko ja tr Kurutma makinesi ... more details
being processed, with cooler temperatures resulting in better performance. Desiccant dryer The term desiccant dryer refers to a broad class of dryers. Other terms commonly used are regenerative dryer ... sieve or other desiccant material. The desiccant can bring the dewpoint of the water vapor in the air ... transition deposition water until it is cooled to 40 degrees Celsius. In practice two cylinders with desiccant ... valves. The regeneration of the desiccant vessel can be during three different methods Heatless pressure swing drying which uses part of the dry compressed air coming from the other vessel to dry the desiccant ... more details
to burn a wide variety of liquid fuels. Desiccant Wheel A desiccant wheel is very similar to a thermal .... The desiccant is normally Silica Gel . As the wheel turns, the desiccant passes alternately through ... the desiccant is dried and the moisture expelled. The wheel continues to rotate and the adsorbent ... or steam coil, or a direct fired gas burner. Thermal wheels and desiccant wheels are often used ... more details
Unreferenced date December 2009 Orphan date October 2006 Humidity buffering refers to the ability of materials to moderate changes in relative humidity by absorbing and desorbing water vapour from surrounding air. This is also referred to as moisture buffering . The phenomenon has long been exploited for preserving items from damage that could be caused by either excessively moist or dry conditions. Examples 1. Cigars are usually kept in a wooden box called a humidor . A pan of water is placed in the humidor so that the wood will absorb water vapor at close to 100 Relative Humidity . It is then used to store the cigars at fairly constant relative humidity, between 45 50 . 2. Silica Gel is widely used in the opposite way, as a desiccant to buffer relative humidity inside museum display cases, packaged clothing, electronics and anything that might be damaged by condensation. Recently, there has been an interest in the field of building science and architecture in using humidity buffering as a passive indoor climate control, thus reducing the need for air conditioning and Ventilation architecture ventilation . br See also Humectant DEFAULTSORT Humidity Buffering Category Atmospheric thermodynamics Category Heating, ventilating, and air conditioning ... more details
of hydrogen CaO Mg H sub 2 sub CaH sub 2 sub MgO Use as a desiccant The reaction of CaH sub 2 ... hydride is a relatively mild desiccant, it is safe compared with more reactive agents such as sodium metal or NaK sodium potassium alloy . Calcium hydride is widely used as a desiccant for base ... reactive desiccant. Drawbacks Although CaH sub 2 sub is indeed convenient and often the drying agent ... more details
used as desiccant s to draw moisture away from water sensitive items. Desiccants should never be placed ... carbon and silica gel the most common ingredients in commercial desiccant packets and will pull and absorb the water from the desiccant packets. Lye should be stored in air tight plastic containers. Glass ... more details
the desiccant packs from the clothing as Plan B, so he only manages to ruin the clothes in about ... chips the store gives out to its customers and unknowingly drops one of the desiccant packs in the salsa ... by eating desiccant from Putumayo s clothing that Kramer spilled into a bowl of Salsa sauce salsa at the store ... more details
readily, making it useful as a desiccant drying agent . Once saturated with water, the gel can be regenerated .... ref name Greenwood Applications Desiccant see also Desiccant In many items, moisture encourages ... more details
chembox verifiedrevid 401033555 Name Magnesium perchlorate ImageFile Magnesium perchlorate.png ImageSize 150px ImageName Magnesium perchlorate OtherNames Section1 Chembox Identifiers ChemSpiderID Ref chemspidercite correct chemspider ChemSpiderID 23223 InChI 1 2ClHO4.Mg c2 2 1 3,4 5 h2 H,2,3,4,5 q 2 p 2 InChIKey MPCRDALPQLDDFX NUQVWONBAH SMILES Mg 2 .O Cl O O O . O Cl O O O StdInChI Ref stdinchicite correct chemspider StdInChI 1S 2ClHO4.Mg c2 2 1 3,4 5 h2 H,2,3,4,5 q 2 p 2 StdInChIKey Ref stdinchicite correct chemspider StdInChIKey MPCRDALPQLDDFX UHFFFAOYSA L CASNo 10034 81 8 CASNo Ref cascite correct CAS PubChem 24840 RTECS SC8925000 Section2 Chembox Properties Formula Mg ClO sub 4 sub sub 2 sub Appearance white powder, br deliquescent MolarMass 223.206 g mol Density 2.21 g cm sup 3 sup Solubility 99.3 g 100 mL Solubility1 24 g 100 mL Solvent1 ethanol MeltingPt 251 C BoilingPt decomposition Section7 Chembox Hazards ExternalMSDS http www.jtbaker.com msds englishhtml a6648.htm External MSDS EUIndex Not listed RPhrases R8 , R36 , R37 , R38 SPhrases S17 , S26 , S27 , S36 , S37 , S39 NFPA H 1 NFPA F 0 NFPA R 0 NFPA O OX Section8 Chembox Related OtherCations Calcium perchlorate br Barium perchlorate Magnesium perchlorate is a powerful oxidizing agent , with the formula Mg ClO sub 4 sub sub 2 sub . Magnesium perchlorate decomposes at 250 C. ref CRC Handbook ref The heat of formation is 568.90 kJ mol sup 1 sup . ref Lange s ref The enthalpy of solution is quite high, so reactions are done in large amounts of water to dilute it. It is sold under the trade name anhydrone. It was used as desiccant to dry gas or air samples, ref cite journal title The Preparation and Properies of Magnesium Perchlorate and its Use as a Drying Agent author H. H. Willard, G. F. Smith journal Journal of the American Chemical Society year 1922 volume 44 issue 10 pages 2255 2259 doi 10.1021 ja01431a022 ref ref cite journal title Preparation of perlite based magnesium perchlorate desiccant with colou ... more details
Moisture Sensitivity Level relates to the packaging and handling precautions for some semiconductors. The MSL is an Electronics electronic standard for the time period in which a moisture sensitive device can be exposed to ambient room conditions approximately 30 C 60 RH . Increasingly, semiconductors have been manufactured in smaller sizes. Components such as thin fine pitch devices and ball grid array s could be damaged during Surface mount technology SMT reflow when moisture trapped inside the component expands. The expansion of trapped moisture can result in internal separation delamination of the plastic from the die or lead frame, wire bond damage, die damage, and internal cracks. Most of this damage is not visible on the component surface. In extreme cases, cracks will extend to the component surface. In the most severe cases, the component will bulge and pop. This is known as the popcorn effect. IPC electronics IPC Association Connecting Electronic Industries created and released IPC M 109, Moisture sensitive Component Standards and Guideline Manual. Moisture sensitive devices are packaged in a moisture barrier antistatic bag with a desiccant and a moisture indicator card which is vacuum sealed. IPC M 109 includes seven documents. According to http www.siliconfareast.com msl.htm IPC JEDEC s J STD 20 Moisture Reflow Sensitivity Classification for Plastic Integrated Circuit IC SMDs, there are eight levels of moisture sensitivity. Components must be mounted and reflowed within the allowable period of time floor life out of the bag . MSL 6 Mandatory Bake before use MSL 5A 24 hours MSL 5 48 hours MSL 4 72 hours MSL 3 168 hours MSL 2A 4 weeks MSL 2 1 year MSL 1 Unlimited Category Integrated circuits Category Semiconductors de Moisture Sensitive Level ... more details
Orphan date January 2011 Image M SG reducing agent.svg right 500px frame M SG reductions benzyl chloride reduction to bibenzyl , dibenzothiophene reduction to biphenyl and naphthalene reduction to dihydronaphthalene In M SG an alkali metal is absorbed into silica gel at elevated temperatures. The resulting black powder material is an effective reducing agent and safe to handle as opposed to the pure metal. The material can also be used as a desiccant and as a hydrogen source ref Alkali Metals Plus Silica Gel Powerful Reducing Agents and Convenient Hydrogen Sources James L. Dye, Kevin D. Cram, Stephanie A. Urbin, Mikhail Y. Redko, James E. Jackson, and Michael Lefenfeld J. Am. Chem. Soc. , 127 26 , 9338 9339, 2005 http pubs.acs.org cgi bin abstract.cgi jacsat 2005 127 i26 abs ja051786 .html Abstract ref . The metal is either sodium or a sodium potassium alloy NaK Na sub 2 sub K . The molten metal is mixed with silica gel under constant agitation at room temperature . This phase 0 material must be handled in an inert atmosphere. Heating phase 0 at convert 150 C F takes it to phase I . When this material is exposed to dry oxygen the reducing power is not affected. At further heating to convert 400 C F phase II can be handled safely in an ambient environment. The metal reacts with the silicon gel in an exothermic reaction in which Na sub 4 sub Si sub 4 sub nanotechnology nanoparticles are formed. The powder reacts with water to form hydrogen . Compounds such as biphenyl and naphthalene are reduced by the powder and form highly coloured radical ion radical anion s. The powder can also be introduced in a column chromatography setup and eluted with organic reactants in order to probe the reducing power. The powder is mixed with additional wet silica gel which provides additional hydrogen. A Birch reduction of naphthalene takes 5 minutes elution time . The column converts benzyl chloride to bibenzyl in a Wurtz coupling and in a similar fashion dibenzothiophene is reduced to ... more details
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