Hygroscopic water content

The three model systems were very hygroscopic. Water contents at different RVPs 44.1% generally leveled off within 24 h. When exposed to RVP 54.5%, the three model systems showed different sorption behaviors (Figure 53.1). Loss of sorbed water indicated time-dependent crystallization. Compared with the lactose/reactant and trehalose/reactant systems, crystallization of component sugars in the lactose/trehalose/reactant system occurred more slowly. At RVP 65.6 and 76.1%, loss of sorbed water in lactose/reactant system was observed after 21 and 8 h of storage, and in trehalose/reactant system after 5 and 3h, respectively, while in lactose/trehalose/reactant system, after 79 and 33 h, respectively. Three model systems sorbed different amoimts of water before showing the loss of water. The higher water content in the lactose/trehalose/reactant system... 

Compression tests with hygroscopic water content... 

The influence of temperature on the compressibility of unsaturated clay has been studied by compression tests in oedometric conditions. The initial dry density of the samples has been 1.70 g/cm, and the clay was compacted uniaxially with its hygroscopic water content inside the oedometer ring (diameter of 5.0 cm, length of the specimen of 1.2 cm). A vertical pressure between 22 and 26 MPa was applied to manufacture the specimens. Three different samples were heated up to 25, 60 and 80 °C under a low vertical load (0.4 MPa). Afterwards, the samples were progressively loaded by steps up to 20 MPa. The tests were performed in an... 

The determination of the swelling pressure as a function of temperature in the interval between 25 and 80 °C has been performed in the oedometers shown in Figure 2. The clay has been uniaxially compacted with its hygroscopic water content at initial dry densities of 1.50 and 1.60 g/cm . Vertical stresses of 11 and 16 MPa, respectively, were applied to obtain specimens of 5.0 diameter and 1.2 cm height. 

Three tests on bentonite compacted at an initial dry density of 1.7 g/cm with its hygroscopic water content have been performed at different temperatures (20, 40 and 60 °C), following the suction and stress paths indicated in Figure 4. In the first step, under a vertical load of 0.1 MPa, the suction of the sample was equalised to 14 MPa (due to mechanical limitations of the cell, this is the maximum suction that can be controlled). Afterwards, keeping this suction constant, the vertical load was increased up to 5 MPa. Under this vertical load, suction was decreased by steps until... 

Liquid cycloahphatic amines and diamines have exacting purity and color standards. Almost all are sold to specification, not performance standards. Use as isocyanate precursors requites low water content criteria for these hygroscopic fluids, hence nitrogen blanketing is often specified for product sampling as well as storage and transport. 

Fischer titration may not be reliable for water concentration determination in the presence of highly hygroscopic electrolytes, e.g., LiCl/DMAc [119]. This conclusion has been also verified for TBAF/DMSO, by adding known amounts of water to the solvent system, followed by determination of the water content by Karl-Fischer titration. Whereas the added water ranged from 0.23 to 1.19 mol H, that determined by titration ranged from 0.21 to... 

Soil is hygroscopic. The water content of air dry soil will increase and decrease as the relative humidity of the air it is exposed to changes. The uptake of water by oven dry soil is shown in Figure 7.10. Thus, determination of water content just before analysis is critical. 

Under indoor conditions, in the same way than outdoors, it is necessary the presence of surface humidity for corrosion to occur due to the electrochemical nature of the atmospheric corrosion process however, in indoor conditions there are no precipitations and the presence of surface water depends mainly on water content in the air and changes in temperature on the surface, as well as the presence of hygroscopic substances on the metallic surface. 

Another potential effect is if one species affects the concentration of others due to chemical interactions. If the concentration of a species that is hygroscopic changes, the water content and average index of refraction for the particle may change simultaneously. For example, a reduction of about 7% in the index of refraction due to increased hydration can lead to a change in the scattering efficiency of as much as 34% (Hegg et al., 1993). 

Urea is used in cream or ointment to make it less greasy, it increases the water content of stratum corneum which may be because of its hygroscopic property. It also possesses keratolytic property. 

Urea increases the water content of the stratum corneum, presumably as a result of the hygroscopic characteristics of this naturally occurring molecule. Urea is also keratolytic. The mechanism of action appears to involve alterations in prekeratin and keratin, leading to increased solubilization. In addition, urea may break hydrogen bonds that keep the stratum... 

The magnitude of the CD has commonly been calibrated at 290 nm using ( + )-camphor-10-sulfonic acid as a standard. Because of its hygroscopic nature, the water content has led to some confusion. Tsujimura et al. have recommended to use a molar ellipticity of +7.78 x 103 for the compound in an aqueous solution 280). The concentration can be calibrated by the ORD of the same sample, which gave a molar rotation of +4.28 x 103 at 305 nm and of —5.44 x 103 at 270 nm. 

Because atmospheric humidity must be avoided, the reaction flask is isolated from the atmosphere with drying tubes. Moreover, since the solvent is rarely perfectly anhydrous and will contain traces of water due to its hygroscopic nature, its water content must be measured prior to the determination. The equivalence point of the titration reaction is detected by an electrical method instead of a visual method. The current intensity that passes between two platinum electrodes inserted in the reaction medium is measured (see Fig. 19.10). The reagent, which is a mixture of sulphur dioxide, iodine and a base, is characterised by the number of mg of water that can be neutralised by 1 cm3 of this reagent. This is referred to as the equivalent mass concentration of water, or the titre T of the reagent. 

Anal calc. For C24H42N2O4. 3H20 C 49.14, H 8.19, N 4.77 Found C 49.04, H 8.03, N 4.75. NB in view of the highly hygroscopic nature of pyrrole-lactobionamide, residual water content is determined by a Karl Fischer apparatus. 

Propylene glycol is also an effective humectant and increases the water content of the stratum corneum. The hygroscopic characteristics of the agent may help it to develop an osmotic gradient through the stratum corneum, thereby increasing hydration of the outermost layers by drawing water out from the inner layers of the skin. 

With topically applied 10% urea ointment, Sasaki et al. showed an improvement of stratum corneum water content, hygroscopicity, and TEWL, in psoriasic patients.56... 

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