The hygroscopic water

The hygroscopic water is water contained in air-dried soils. The content of this water varies depending on the relative humidity and on the soil properties particularly the granulometric composition and humus content of the soil affect its amount. 

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Determination of the Hygroscopic Water.—About io grams of the substance are dried at ioo° to constant weight. 

Natural umbers contain somewhat variable amounts of hygroscopic water (up to 20% or more), and the loss on ignition usually varies from 7 to 11%. The dried earth contains much less hygroscopic moisture (about 6%),but the whob of the combined water, so that the loss on Calcination is the same as with the natural earths. The burnt earth contains little hygroscopic water (usually less than 5%) and give a loss of 3-4% on calcination. In general it may be said that when an umber loses less than 5% on calcination, it is burnt —this independently of the hygroscopic water, which may be considerable even in burnt umber if this has been stored in a moist place. 

The content of the hygroscopic water in air-dried soils is determined by a gravimetric method, similarly as the moisture in fresh soils, by drying at 105°C to constant weight. 

The above nomenclature can, without any difhculty, be made compatible with the electrochemical terminology. The hygroscopic water corresponds to the IHL the solvation water to the term OHL, and the captive water to the term diffuse layer. In addition, the colloid structure provides for an interface between the OHL and the diffuse layer, called outer Helmholtz plane (OHP), the precondition for any and all electrochemical reactions. The electrical potential between the OHL and the diffuse layer is known as zeta potential, or electrokinetic potential. 

Physical Properties. All colourless liquids, completely miscible with water, except benzyl alcohol and cyclohexanol, which are slightly soluble. Pure glycol and glycerol have high viscosity, which falls as the hygroscopic liquids absorb water from the air. 

Iron(III) bromide [10031-26-2], FeBr, is obtained by reaction of iron or inon(II) bromide with bromine at 170—200°C. The material is purified by sublimation ia a bromine atmosphere. The stmcture of inoa(III) bromide is analogous to that of inon(III) chloride. FeBr is less stable thermally than FeCl, as would be expected from the observation that Br is a stronger reductant than CF. Dissociation to inon(II) bromide and bromine is complete at ca 200°C. The hygroscopic, dark red, rhombic crystals of inon(III) bromide are readily soluble ia water, alcohol, ether, and acetic acid and are slightly soluble ia Hquid ammonia. Several hydrated species and a large number of adducts are known. Solutions of inon(III) bromide decompose to inon(II) bromide and bromine on boiling. Iron(III) bromide is used as a catalyst for the bromination of aromatic compounds. 

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. 

The low water absorption of the polymer avoids the necessity of predrying before processing except where hygroscopic additives are present. 

The nylons are hygroscopic. Figure 18.16 shows how the equilibrium water absorption of different nylons varies with humidity at room temperature. Figure 18.17 shows how the rate of moisture absorption is affected by the environmental conditions. 

Another problem is that K2NbOF5 is extremely hygroscopic. The absorbed water converts the compound into ciystal hydrate ... 

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... 

Analysis From the graph of the stress test results, linear regression is seen to be appropriate (this in effect means that at these small quantities of water vapor the hygroscopic tablets are far from thermodynamic saturation). The slopes, in mg of water per day per pouch, are compared ... 

For the same adsorbent, different mobile phases can be used according to the aim of chromatographic analysis. Rather than preparing an endless line of chromatographic plates of different thickness, it is easier to change the mobile phase up to the most convenient composition, keeping the same characteristics of the stationary phase. In the case of a hygroscopic adsorbent, the adsorbed water influences its activity. 

The boundary conditions for the system are (1) that at the surface of the hygroscopic material the partial pressure of water is determined by that of the saturated salt solution (Ps) and (2) that at a characteristic distance from the surface (8) the partial pressure of water vapor is given by the chamber pressure (Pc). 

An undesirable effect of the hygroscopic nature of nylons is that we must take care that they are dry before trying to process them in the molten state. If we were to attempt to extrude wet nylon, the water would vaporize within the extruder, creating bubbles in the melt. The result would be a non-uniform extrudate containing voids and exhibiting an uneven surface texture. 

Addition of water to an intimate mixture of zinc powder and the salts causes spontaneous ignition [1], and a mixture of ammonium nitrate and ammonium chloride (9 1) sprinkled with zinc dust ignites vigorously when moistened [2], Premature spontaneous ignition of the mixture was attributed to absorption of moisture by the hygroscopic salt mixture [3],... 

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