Moisture hygroscopic

Equilibrium moistures (hygroscopic points) in AN determined by static or flow methods do not agree. In general, flow methods are recommended. To increase the rate of moisture exchange (at a given RH) the temp of system should be raised (Ref 11)... 

Pyridine. The analytical reagent grade pyridine will satisfy most requirements. If required perfectly dry, it should be refluxed over potassium or sodium hydroxide pellets or over barium monoxide, and then distilled with careful exclusion of moisture (compare Fig. 77, 47, 2). It is hygroscopic, and forms a hydrate of b.p. 94-5°. Pure pyridine has b.p. 115-5°/760 mm. 

The solid appears to be a mixture of the complexes CH,COOH.BF, and 2CH COOH.BF,. The latter appears to be a liquid and is alone soluble in ethylene dichloride the former is a solid. The solid moiioocetic acid complex is obtained by saturating an ethylene dichloride solution of acetic acid with boron trifluoride, filtering and washing the precipitate with the solvent it is hygroscopic and should be protected from moisture. It may be used as required 0-75 mol is employed with 0-26 mol of ketone and 0 6 mol of anhydride. 

Butynediol soHd flakes are packed in polyethylene bags inside dmms. The product is hygroscopic and must be protected from moisture. 

Shipment, Stora.ge, ndPrice. Butyrolactone is shipped in unlined steel tank cars and plain steel dmms. Plain steel, stainless steel, aluminum, and nickel are suitable for storage and handling mbber, phenoHcs, and epoxy resins are not suitable. Butyrolactone is hygroscopic and should be protected from moisture. Because of its low free2ing point (—44° C), no provision for heating storage vessels is needed. 

Control of relative humidity is needed to maintain the strength, pHabiUty, and moisture regain of hygroscopic materials such as textiles and paper. Humidity control may also be required in some appHcations to reduce the effect of static electricity. Temperature and/or relative humidity may also have to be controlled in order to regulate the rate of chemical or biochemical reactions, such as the drying of varnishes, the appHcation of sugar coatings, the preparation of synthetic fibers and other chemical compounds, or the fermentation of yeast. 

Most textile fibers are hygroscopic at least to some extent, and therefore capable of absorbing moisture from the atmosphere, which is a direct reflection of chemical stmcture. Textile fibers vary from those that may be considered hydrophilic to those that are essentially hydrophobic (8—10). 

Aloisture Absorbent Synthetic Paper. Processes for making a water absorbent synthetic paper with dimensional stabihty have been developed by several companies. In a process developed by Mitsubishi Rayon, acrylic fiber is insolubilized by hydra2ine and then hydroly2ed with sodium hydroxide. The paper, formed from 100 parts fiber and 200 parts pulp, has a water absorption 28 times its own weight (96). Processes for making hygroscopic fibers have also been reported in the patent Hterature. These fibers are used in moisture absorbing nonwovens for sanitary napkins, filters, and diapers. 

Moisture Absorbency. PVA fiber is more hygroscopic than any other synthetic fiber. The hygroscopicity varies depending on how the fiber is processed after spinning, ie, in heat-drawing, he at-treatment, acetalization, and the like. 

Anhydrous oxaUc acid normally melts and simultaneously decomposes at 187°C. Sublimation starts at slightly below 100°C and proceeds rapidly at 125°C partial decomposition takes place during sublimation at 157°C. Anhydrous oxaUc acid is hygroscopic and thus absorbs moisture in the air to form the dihydrate. 

Properties. Anhydrous aluminum chloride is a hygroscopic, white soHd that reacts with moisture ia air. Properties are shown ia Table 1. Commercial grades vary ia color from light yellow to light gray as a result of impurities. Crystal size is dependent upon method of manufacture. At atmospheric pressure, anhydrous aluminum chloride sublimes at 180°C as the dimer [13845-12-0] Al2Qg, which dissociates to the monomer beginning at... 

Shipment and Storage. 2-Pyrrohdinone is available in steel dmms and in aluminum or stainless-steel tank cars and tank trailers. Because of its high freezing point, bulk shipments are in tanks with heating coils. Heating with hot water rather than steam avoids product discoloration. Steel (qv), stainless steel, and aluminum are satisfactory materials for storage containers. Because 2-pyrrohdinone is hygroscopic, it must be protected from atmospheric moisture. 

Shipment, Stora.ge, ndPrice. l-Methyl-2-pyrrohdinone is available in tank cars or tank trailers as well as in dmms. Shipping containers are normally of unlined steel. Rubber hose is unsuitable for handling standard steel pipe or braided steel hose is acceptable. Ordinarily 1020 carbon steel (0550) is satisfactory as a storage material. Stainless-steel 304 and 316, nickel, and aluminum are also suitable. MethylpyrroHdinone is hygroscopic and must be protected from atmospheric moisture. In September 1994, NMP was Hsted at 3.89/kg. 

The hygroscopic and humectant properties of com symps are of great importance in many apphcations. Depending on the type of symp and on the specific conditions of temperature and humidity, the products may either resist or facihtate moisture loss or moisture absorption. The abihty to attract moisture or retard its loss increases with increasing DE value. Prevention of moisture pickup is more characteristic of symps having low DE values. 

Table 3 fists some of the physical and chemical properties of vitamin > 2 (1)35). Crystalline vitamin > 2 is stable in air and is not affected by moisture. The anhydrous compound, however, is very hygroscopic, and when exposed to moist air may absorb about 12% of water. 

Adsorption. Wood is highly hygroscopic. The amount of moisture adsorbed depends mainly on the relative humidity and temperature (Fig. 1). Exceptions occur with species with high extractive contents (eg, redwood, cedar, and teak). The equihbtium moisture contents of such woods ate generally... 

In green wood, the cell walls are saturated, whereas some cell cavities are completely filled and others may be completely empty. Moisture ia the cell walls is called bound, hygroscopic, or adsorbed water. Moisture ia the cell cavities is called free or capillary water. The distiaction is made because, under ordinary conditions, the removal of the free water has Htde or no effect on many wood properties. On the other hand, the removal of the cell wall water has a pronounced effect. 

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