Absorption of water

A modification of the conventional soy protein isolate process has been investigated on a small pilot-plant scale. It is based on the absorption of water from the aqueous protein after extraction at pH 8.5 using temperature-sensitive polyisopyropylacrylamide gels, followed by spray drying to give a 96% protein isolate (111). 

Castor oil is a cathartic only after Hpolysis in the small intestine Hberating ricinoleic acid. Ricinoleic acid inhibits the absorption of water and electrolytes. It is commonly used for preparation of the large bowel for diagnostic procedures. 

Sodium and potassium ions are actively absorbed from the intestine. As a consequence of the electrical potential caused by transport of these ions, an equivalent quantity of Cf is absorbed. The resulting osmotic effect causes absorption of water (56). 

Morta.r, Mortar, principally slaked lime and sand, sets because of the evaporation of water, the deposition of calcium hydroxide, and the absorption of water by the bricks or cement blocks, foUowed by hardening as a result of the absorption and reaction of carbon dioxide. 

Note that the group on the left side of Eq. (14-182) is dimensionless. When turbulence promoters are used at the inlet-gas seclion, an improvement in gas mass-transfer coefficient for absorption of water vapor by sulfuric acid was obsei ved by Greenewalt [Ind. Eng. Chem., 18, 1291 (1926)]. A falhug off of the rate of mass transfer below that indicated in Eq. (14-182) was obsei ved by Cogan and Cogan (thesis, Massachusetts Institute of Technology, 1932) when a cauTiiug zone preceded the gas inlet in ammonia absorption (Fig. 14-76). 

Sodium sulfate (anhydrous). Has a large capacity for absorption of water, forming the decahydrate below 33°, but drying is slow and inefficient, especially for solvents that are sparingly soluble in water. It is suitable for the preliminary drying of most types of organic compounds. 

Fractionally distd below ISmm pressure, using packed column and taking precautions to avoid absorption of water. 

The r values from Eq. (5-1) for the most important materials for pipe coatings are given in Table 5-1. Table 5-2 contains results of long-term field experiments. For comparison, the values of r°are included in Table 5-1. It can be seen that values are always smaller than r values, which is apparently due to the absorption of water when the coating is immersed in the medium. A marked reduction in the coating resistance has been observed with increasing temperature for resins [9,13,14] (see Fig. 5-2 [14]). 

Mass concentration units for ambient measurements are mass (/xg) per unit volume (m ). Size classification involves the use of specially designed inlet configurations, e.g., PMjq sampling. To determine mass concentration, all the particles are removed from a known volume of air and their total mass is measured. This removal is accomplished by two techniques, filtration and impaction, described in Chapter 13. Mass measurements are made by pre-and postweighing of filters or impaction surfaces. To account for the absorption of water vapor, the filters are generally equilibrated at standard conditions T = 20°C and 50% relative humidity). 

Three months immersion in water leads to a 5% w/w absorption of water which at this level leads to a reduction in the heat distortion temperature (ISO) of 100 Celsius degrees. 

Weathering. This generally occurs as a result of the combined effect of water absorption and exposure to ultra-violet radiation (u-v). Absorption of water can have a plasticizing action on plastics which increases flexibility but ultimately (on elimination of the water) results in embrittlement, while u-v causes breakdown of the bonds in the polymer chain. The result is general deterioration of physical properties. A loss of colour or clarity (or both) may also occur. Absorption of water reduces dimensional stability of moulded articles. Most thermoplastics, in particular cellulose derivatives, are affected, and also polyethylene, PVC, and nylons. 

Water resistance. Coatings must show a negligible absorption of water and must be highly impermeable to water or water-vapour transmission. 

Table 9. Absorption of water and aqueous solutions by several supergels [58]...

M2 Thickener It is pulverized Ml thickener with an antimoisture substance (attasorb clay) added in the ratio of lp attasorb clay to 19p Ml thickener. It readily absorbs moisture from the air, but not to the extent of M1 thickener, because less air circulates thru the pulverized particles the attasorb clay further lowers moisture absorption. A container may be resealed after part of the M2 thickener has been used provided it has had minimum exposure to air. Since M2 thickener is composed mainly of Ml thickener, it retains most of the characteristics of Ml, including the disadvantages of being manufd from critical material, absorption of water from the air, and sensitivity to moisture. 

The simple relation (6.1) is quite useful. It allows an estimate of the gain or loss in yield strength if the glass transition temperature is changed, as for instance by the progress of the curing reaction, by radiation damage, or by absorption of water and of solvents. The ATe is determined fairly easily by thermoanalytical measurements. 

Plutonium(IV) polymer has been examined by infrared spectroscopy (26). One of the prominent features in the infrared spectrum of the polymer is an intense band in the OH stretching region at 3400 cm 1. Upon deuteration, this band shifts to 2400 cm 1. However, it could not be positively assigned to OH vibrations in the polymer due to absorption of water by the KBr pellet. In view of the broad band observed in this same region for I, it now seems likely that the bands observed previously for Pu(IV) polymer are actually due to OH in the polymer. Indeed, we have observed a similar shift in the sharp absorption of U(0H)2S0ir upon deuteration (28). This absorption shifts from 3500 cm 1 to 2600 cm 1. 

Due to the absorption of water, the specific gravity of clays is highly variable and is lowered with increased water content. 

TCA occurs naturally as a colorless crystal and is easily formulated by mixture with distilled water. TCA is stable under normal conditions with a melting point of 54 deg Celsius. It is not light sensitive however, it is hygroscopic so the crystals should be stored in a closed container to limit its absorption of water. Once mixed, TCA has a shelf life of at least 2 years. 

As the cement ages, absorption of water and loss of aluminium ions ceases (after 7 days). Other species - sodium and fluoride ions and silicic acid - continue to be eluted. The release of fluoride is important, for the glass polyalkenoate cement can be seen as a device for its sustained release. 

Elution of ions is accompanied by absorption of water and this can amount to as much as 20% by mass in five days (Kuhn et al., 1982). The extent of water uptake is affected by the ionic concentration of the solution. 

The contact angle with formamide remained almost the same. As shown in Figure 5, the contact angle with water further decreased in time since the absorption of water by pHEMA incorporated in PET is accompanied by swelling of the hydrogel, thereby increasing the surface polarity and ability of the film to be wetted. 

GL Amidon, GD Lessman, RL Elliot. Improving intestinal absorption of water-insoluble compounds A membrane metabolism strategy. J Pharm Sci 69 1363, 1980. 

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