Sodium chloride, properties

Fig. XIII-9. The dependence of the flotation properties of goethite on surface charge. Upper curves are potential as a function of pH at different concentrations of sodium chloride lower curves are the flotation recovery in 10 M solutions of dodecylammo-nium chloride, sodium dodecyl sulfate, or sodium dodecyl sulfonate. (From Ref. 99.)...

The above simple experiments illustrate the more important properties of aliphatic acid chlorides. For characterisation, the general procedure is to hydrolyse the acid chloride by warming with dilute alkali solution, neutralise the resulting solution with dilute hydrochloric acid (phenol-phthalein), and evaporate to dryness on a water bath. The mixture of the sodium salt of the acid and sodium chloride thus obtained may be employed for the preparation of solid esters as detailed under Aliphatic Acids, Section 111,85. The anilide or p-toluidide may be prepared directly from the acid chloride (see (iii) above and Section III,85,i). 

Sensory perception is both quaUtative and quantitative. The taste of sucrose and the smell of linalool are two different kinds of sensory perceptions and each of these sensations can have different intensities. Sweet, bitter, salty, fmity, floral, etc, are different flavor quaUties produced by different chemical compounds the intensity of a particular sensory quaUty is deterrnined by the amount of the stimulus present. The saltiness of a sodium chloride solution becomes more intense if more of the salt is added, but its quaUty does not change. However, if hydrochloric acid is substituted for sodium chloride, the flavor quahty is sour not salty. For this reason, quaUty is substitutive, and quantity, intensity, or magnitude is additive (13). The sensory properties of food are generally compHcated, consisting of many different flavor quaUties at different intensities. The first task of sensory analysis is to identify the component quahties and then to determine their various intensities. 

High Surface Sodium. Liquid sodium readily wets many soHd surfaces. This property may be used to provide a highly reactive form of sodium without contamination by hydrocarbons. Powdered soHds having a high surface area per unit volume, eg, completely dehydrated activated alumina powder, provide a suitable base for high surface sodium. Other powders, eg, sodium chloride, hydride, monoxide, or carbonate, can also be used. 

In converting ESBR latex to the dry mbber form, coagulating chemicals, such as sodium chloride and sulfuric acid, are used to break the latex emulsion. This solution eventually ends up as plant effluent. The polymer cmmb must also be washed with water to remove excess acid and salts, which can affect the cure properties and ash content of the polymer. The requirements for large amounts of good-quaUty fresh water and the handling of the resultant effluent are of utmost importance in the manufacture of ESBR and directly impact on the plant operating costs. 

The choice of coagulant for breaking of the emulsion at the start of the finishing process is dependent on many factors. Salts such as calcium chloride, aluminum sulfate, and sodium chloride are often used. Frequentiy, pH and temperature must be controlled to ensure efficient coagulation. The objectives are to leave no uncoagulated latex, to produce a cmmb that can easily be dewatered, to avoid fines that could be lost, and to control the residual materials left in the product so that damage to properties is kept at a minimum. For example, if a significant amount of a hydrophilic emulsifier residue is left in the polymer, water resistance of final product suffers, and if the residue left is acidic in nature, it usually contributes to slow cure rate. 

The properties of compounds are very different from those of the elements they contain. Ordinary table salt, sodium chloride, is a white, unreactive solid. As you can guess from its name, it contains the two elements sodium and chlorine. Sodium (Na) is a shiny, extremely reactive metal. Chlorine (Cl) is a poisonous, greenish-yellow gas. Clearly, when these two elements combine to form sodium chloride, a profound change takes place (Figure 1.3, page 4). 

Though many solutions are colorless and closely resemble pure water in appearance, the differences among solutions are great. This can be demonstrated with the five pure substances, sodium chloride (salt), iodine, sugar, ethyl alcohol, and water. Two of these substances, ethyl alcohol and water, are liquids at room temperature. Let s investigate the properties of the solutions these two substances form. 

We have, in this chapter, encountered a number of properties of solids. In Table 5-II, we found that melting points and heats of melting of different solids vary widely. To melt a mole of solid neon requires only 80 calories of heat, whereas a mole of solid copper requires over 3000 calories. Some solids dissolve in water to form conducting solutions (as does sodium chloride), others dissolve in water but no conductivity results (as with sugar). Some solids dissolve in ethyl alcohol but not in water (iodine, for example). Solids also range in appearance. There is little resemblance between a transparent piece of glass and a lustrous piece of aluminum foil, nor between a lump of coal and a clear crystal of sodium chloride. 

When we study a solid that does not have the characteristic lustrous appearance of a metal, we find that the conductivity is extremely low. This includes the solids we have called ionic solids sodium chloride, sodium nitrate, silver nitrate, and silver chloride. It includes, as well, the molecular crystals, such as ice. This solid, shown in Figure 5-3, is made up of molecules (such as exist in the gas phase) regularly packed in an orderly array. These poor conductors differ widely from the metals in almost every property. Thus electrical conductivity furnishes the key to one of the most fundamental classification schemes for substances. 

Referring to Tables 5-1 and 5-II, we find that both sodium chloride and copper have extremely high melting and boiling points. These two solids have little else in common. Sodium chloride has none of the other properties that identify a metal. It has no luster, rather, it forms a transparent crystal. It does not conduct electricity nor is it a good heat conductor. The kind of forces holding this crystal together must be quite different from those in metals. 

The compound sodium hydride, formed in reaction (29), is a crystalline compound with physical properties similar to those of sodium chloride. The chemical properties are very different, however. Whereas sodium burns readily in chlorine, it reacts with hydrogen only on heating to about 300°C. While sodium chloride is a stable substance that dissolves in water to form Na+(aqJ and CV(aq), the alkali hydrides bum in air and some of them ignite spontaneously. In contact with water, a vigorous reaction occurs, releasing hydrogen ... 

However they are formed, and from whatever source, aqueous ions are individual species with properties not possessed by the materials from which they came. Furthermore, the properties of a particular kind of ion are independent of the source. Chloride ions from sodium chloride, NaClfsJ, have the same properties as chloride ions in an aqueous solution of hydrochloric acid, HQ. In a mixture of the two, all of the chloride ions act alike none remembers whether it entered the solution from an ionic NaQ lattice or from a gaseous HC1 molecule. 

The dissolving of electrolytes in water is one of the most extreme and most important solvent effects that can be attributed to electric dipoles. Crystalline sodium chloride is quite stable, as shown by its high melting point, yet it dissolves readily in water. To break up the stable crystal arrangement, there must be a strong interaction between water molecules and the ions that are formed in the solution. This interaction can be explained in terms of the dipolar properties of water. 

But there is a second notion, which Mendeleev sometimes called "real dements," in order to indicate their more fundamental status. In Bis sense, Ihe eh emants represent abstract substances that lack what wc normally regard as properties and that represent the form that elements take when they occur in compounds. For example, sodium and chlorine as simple substances—a grey mrt.il and a gicmish gas respectively—are nol literally present in the compound sodium chloride (table salt). Mendeleev would have said Brat sodium and chlorine are present In the compound as the abstract or "real ctemanls. ... 

The elucidation of the factors determining the relative stability of alternative crystalline structures of a substance would be of the greatest significance in the development of the theory of the solid state. Why, for example, do some of the alkali halides crystallize with the sodium chloride structure and some with the cesium chloride structure Why does titanium dioxide under different conditions assume the different structures of rutile, brookite and anatase Why does aluminum fluosilicate, AljSiCV F2, crystallize with the structure of topaz and not with some other structure These questions are answered formally by the statement that in each case the structure with the minimum free energy is stable. This answer, however, is not satisfying what is desired in our atomistic and quantum theoretical era is the explanation of this minimum free energy in terms of atoms or ions and their properties. 

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