Dessicant material

Anhydrous An anhydrous material does not contain any water molecules. Many substances occur naturally as hydrates, compounds that have a specific number of water molecules attached to them. This water can often be removed by heating and/or vacuum to give the anhydrous material. Anhydrous materials can absorb water from their surroundings and find use as dessicants. Examples include those packets of silica gel you find in some consumer goods, as well as dehumidifying sachets used in clothes closets. When an anhydrous material reacts with water, this could release a large amount of heat, possibly leading to a heat or pressure buildup that could result in an explosion. 

Sodium dodecylsulfonate (SDS) was prepared from dodecyl alcohol by Ben Den Chemical Company, Naperville, IL. The material was recrystallized by dissolution in hot ethanol solution, filtering and cooling to crystallize the SDS. The precipitate was filtered, washed with cold ethanol, and dried in a dessicator under vacuum. Analytical-grade HCl and NaOH were used for pH adjustment and NaCl for controlling ionic strength. 

The impure material is digested in 250ml water with the required amount of Ag-aSO at 60°C until the precipitate appears well settled (about 1 hour). After being cooled, filtered through asbestos, and evaporated, the clear filtrate is evaporated to dryness on the steam bath. It is placed in a dessicator to remove final traces of moisture. The yield is variable, depending on the purify of the MnO and the success of the oxidative fusion, but it should be 30-60g. 

Heating drives off the H20 without destroying the structure. The remaining material is hydrophilic and often used as a dessicant. Zeolites also facilitate ion... 

Ferrandon, et a1. (2008) have demonstrated experimentally the scientific practicality of the hydrolysis reaction to produce HC1 gas and solid copper oxychloride. In order to vary the particle sizes, the material was first dried in a dessicator, cmshed and sieved to the desired particle sizes and then re-hydrated. During the hydrolysis experiments, the sample was heated rapidly (within 10 minutes) in humidified Ar to the reaction temperature, between 300 and 400°C, and then held at the test temperature for a fixed period. 

Maintain samples in a dessicated environment. A sample brought to the laboratory in a non-controlled container should be dessicated 2it hours before attempting to characterize the material. 

Where the bubbles are caused by air or water in the substrate, another application of hot asphalt will again expand the water or air in the substrate and again cause blisters. Repeated applications will continue to cause blisters as long as water or air is present. It is, therefore, a waste of time to apply more hot material before removing the source of the trouble. The best procedure is to dry the area thoroughly with heat or with a dessicant or both. If time does not permit, and there is not a great deal of moisture or air present, it may be possible to seal the surface with a concrete sealer, such as an amide-hardened epoxy, and then apply the primer and hot asphalt over this. 

Scale-up operations in the kilo lab are often more similar to process research than to pilot plant operations. With kilo lab operations the key is to prepare the desired material by the deadline, using whatever means are appropriate. For instance, Na2S04 or MgS04 may be used for drying product-rich extracts. (It should be noted that ionizable and polar compounds will adsorb to such dessicants.) Reaction streams may be transferred by pouring or concentrated by rotary evaporation. Compounds may be purified by column chromatography or even triturating. Timely preparation of the desired material is the key for kilo lab work. 

Porous particles contain up to 20% moisture adsorbed tn pores and on the surface. Calculations that use the weight of the catalyst should always correct for this. Bxact moisture content is determined by heating a pre weighed sample in a crucible at temperatures above I000 C. All volatile material, adsorbed moisture, and any constitutional water is removed. The sample is cooled in a dessicator and weighed. 

Alcan AA. [Alcan] Acdvated alumina in selecdve absorpdon processes as stardng material for catalyst as dessicant for drying of gases. 

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