Sodium chloride, crystal structure water solution

FIGURE 7.9 The limiting elongation of sodium chloride crystals as a function of temperature in air and upon contact with zinc chloride and aluminum chloride. (From Skvortsova, Z.N. et al.. Mechanics of fracture of cohesive boundaries with different concentrations of foreign inclusions, in The Successes of Colloid Chemistry and Physical-Chemical Mechanics, E.D. Shchukin (Ed.), Nauka, Moscow, Russia, 1992, pp. 222-228 Traskin, V.Y. et al., Doklady AN SSSR, 191, 876, 1970 Traskin, V.Y. and Skvortsova, Z.N., Thermodynamic activity of water in electrolyte solutions and their impact on the strength of solids, in Surface Water Films in Dispersed Structures, E.D. Shchukin (Ed.), Izd. MGU, Moscow, Russia, 1988, pp. 197-202.)... 

For preparing lakes, a solution of aluminium sulfate (or chloride) is mixed with sodium carbonate, forming fresh alumina Al(OH)3. The colorant is then added and adsorbed on the surface of alumina. Usually the content of colorant in the lake ranges from 10 to 40%." The product is filtered, washed with water, dried, and milled. The product is allowed to contain unreacted alumina but must not contain more than 0.5% HCl-insoluble matter and not more than 0.2 % ether-extractable matter. - Lakes are insoluble in most solvents used for pure dyes, and they have high opacity and better stability to light and heat. Lakes impart their color by dispersion of solid particles in the food. The coloring properties of lakes depend on particles, crystal structures, concentrations of dye, etc. 

Some salts, such as sodium chloride, copper carbonate and sodium nitrate, crystallise in their anhydrous forms (without water). However, many salts produce hydrates when they crystallise from solution. A hydrate is a salt which incorporates water into its crystal structure. This water is referred to as water of crystallisation. The shape of the crystal hydrate is very much dependent on the presence of water of crystallisation. Some examples of crystal hydrates are given in Table 8.6 and shown in Figure 8.20. 

Evaporation of the water from salt solutions results in solid salt crystals the ions involved form an ion lattice corresponding to the salt structure. If one allows the water to slowly evaporate from the saturated solution, this often results in large and beautiful crystals. Particularly the alum salt, when growing crystals from saturated solutions (E4.1), results in beautifully formed octahedron (see Fig. 4.4). In the process, K+(aq) ions, Al3+(aq) ions and S042- ions join together to form an ion lattice of cubic symmetry. If one adds approximately 10% of urea to a saturated sodium chloride solution the salt crystals do not crystallize in the expected cubic form, but in an octahedron form with identical symmetry elements as the cube. 

Water absorbs microwave energy about 10 times better than ice. This is apparently due to the crystal structure of ice inhibiting rotation of the water molecules. Distilled water is a polar insulator, and while it absorbs microwave rather well, a 0.5 molal sodium chloride-distilled water solution absorbs 50% more efficiently. Carbon is nonpolar, but its conductivity is such that it is a respectable microwave absorber. In practice, researchers have elucidated many of the principles involved in microwave and RF energy use and one can formulate an ink or coating with these principles in mind, but the ultimate test is the rate at which the formulated product interacts with microwave energies. 

A. Dyer The water content was determined by T.G.A. We assess the variable H20 content shown in Table I as possibly being caused by breakdown of crystal structure occurring at the initial exchange step. All samples were allowed to equilibrate over a saturated solution of sodium chloride for one week before x-ray examination. 

Smurov precipitated nickel carbonate by mixing aqueous sodium carbonate and nickel chloride solutions. The solid phase obtained was washed free of chloride and used for the solubility study, but no attempt was made to characterise its stoichiometry and/or its crystal structure. The precipitate was equilibrated with water in a temperature range between 278.15 and 353.15 K. For each temperature the partial pressure of carbon dioxide was varied from 0.0005 atm to = 1 atm. Smurov s data have been ex-... 

Solvent casting and particulate leaching (SC/PL) is a simple and commonly used method for fabricating scaffolds for tissue engineering. With an appropriate thermal treatment, porous constructs of synthetic biodegradable polymers can be prepared with specific porosity, surfaceivolume ratio, pore size and crystallinity for different applications. This method involves mixing water-soluble salt (e.g. sodium chloride, sodium citrate) particles into a polymer solution. The mixture is then cast into the mould of the desired shape. After the solvent is removed by evaporation or lyophilization, the salt particles are leached out to obtain a porous structure with the pore shape limited to the cubic crystal shape of the salt. Removal of soluble particles from the interior of a polymer matrix is difficult and limits the thickness of the films prepared to ca. 2 mm [293]. 

Copper (I) iodide is a dense, pure white solid, crystallizing with a zinc-blende structure below 300°. It is less sensitive to light than either the chloride or bromide, although passage of air over the solid at room temperature in daylight for 3 hours results in the liberation of a small amount of iodine. It melts at 588°, boils at 1,293°, and unlike the other copper halides, is not associated in the vapor state. Being extremely insoluble (0.00042 g./l. at 25°), it is not perceptibly decomposed by water. It is insoluble in dilute acids, but dissolves in aqueous solutions of ammonia, potassium iodide, potassium cyanide, and sodium thiosulfate. It is decomposed by concentrated sulfuric and nitric acids. 

Loss of water usually causes a breakdown in the structure of the crystal this is commonly seen with sodium sulfate, whose vapor pressure is sufficiently large that it can exceed the partial pressure of water vapor in the air when the relative humidity is low. What one sees is that the well-formed crystals of the decahydrate undergo deterioration into a powdery form, a phenomenon known as efflorescence. When a solid is able to take up moisture from the air, it is described as hygroscopic. A small number of anhydrous solids that have low vapor pressures not only take up atmospheric moisture on even the driest of days, but will become wet as water molecules are adsorbed onto their surfaces this is most commonly observed with sodium hydroxide and calcium chloride. With these solids, the concentrated solution that results continues to draw in water from the air so that the entire crystal eventually dissolves into a puddle of its own making solids exhibiting this behavior are said to be deliquescent. 

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