Sodium, chloride

Sodium chloride (SO-dee-um KLOR-ide) is a colorless to white powder or crystalline solid with no odor and a characteristic salty taste. It is slightly hygroscopic, meaning that it tends to absorb moisture from the air and become damp. 

Salt is probably one of the best known and most widely used of all chemical compounds. Humans have been using salt as a preservative and to flavor foods since the beginning of recorded time. One of the earliest mentions of sodium chloride dates to 2,700 in the Chinese book Peng Tzao Kan Mu, probably the first book on pharmacology ever written. Access to salt resources has often been a contentious issue among peoples, leading to battles and wars over its ownership. It has been considered at times to be so valuable that it was used as a form of money. Today, sodium chloride has a host of applications beyond its use as a food additive. 

Sodium chloride. Turquoise atom is sodium and green atom is chloride, publishers 

Sodium chloride occurs naturally as the mineral halite and abundantly in the oceans, where it is found in seawater at an average concentration of about 2.6 percent. There are several methods for harvesting salt, some of which date to ancient times. The earliest known method of production is also the simplest evaporation of seawater by the Sun. In this method, seawater is collected in large, shallow ponds and allowed to evaporate. The salts dissolved in the water crystallize on the bottom of the ponds and can be scraped off and the individual compounds present—including sodium chloride-separated from each other. 

This method works best in hot, arid parts of the world. In cooler, moister regions, seawater must be collected in large containers that can be heated artificially. In many cases, the seawater is heated under reduced pressure to allow it to boil at a lower temperature and save heating costs. Again, crystals of sodium chloride (and other dissolved salts) form as the water boils away. 

CHEMICAL NAME = sodium chloride CAS NUMBER = 7647-14-5 MOLECULAR FORMULA = NaCl MOLAR MASS = 58.4 g/mol COMPOSITION = Na(39.3°/o) Cl(69.7°/o) 

MELTING POINT = 80 BOILING POINT = 1,465°C DENSITY = 2.16 g/cm3 

The three main industrial methods used to produce salt are the solar evaporation method, mining of rock salt, and solution mining. The solar evaporation method is the oldest process used to obtain salt. This method is applied in geographic areas with high solar input and low 

A third major process for extracting salt is solution mining this is especially useful for concentrated deep deposits. In solution mining injection wells are drilled into a salt deposit and water is pumped into it. The salt dissolves in the water to produce brine that is pumped back to the surface where it is processed to obtain salt. 

Sodium chloride has numerous uses one major producer lists more than 1,400 uses for its salt. Global production of salt is about 230 million tons annually about 50,000 tons are produced in the United States. The largest consumer of salt is the chemical industry, which uses approximately 60% of total production. The major chemical industry that uses salt is the chlor-alkali industry to produce soda ash (in countries that do not obtain it from natural deposits), caustic soda (NaOH), and chlorine (see Sodium Carbonate and Sodium 

The effect of Na+ on the stability of water-in-oil emulsions is exercised mainly through its influence on sodium caseinate. It has been shown that as the surface concentration of casein on oil droplets is increased, the oil-in-water emulsion becomes less susceptible to flocculation/coalescence in the presence of electrolyte. Added NaCl broadens the droplet size distribution at a low casein content (0.25%) but causes this effect at a high casein content (0.5%) only when CaCl2 is added (Dickinson et al., 1984). 

Data reported for the protolysis constant of water in sodium chloride media are listed in Table 5.10. The data have been acquired across a temperature range of 0-300 °C, with a number of studies obtaining data at 25 °C and the data at other temperatures coming from Busey and Mesmer (1978). 

Robinson and Stokes (1959) presented osmotic coefficient data for NaCl solutions at 25°C, whereas Liu and Lindsay (1972) gave data for 75-300 C. Equation (5.18) was used to determine water activity data that were derived from 

The data listed in Table 5.11 can be described by the following temperature-dependent equations  

As indicated, Table 5.14 compares the protolysis constant data using Eqs. (5.17) and (5.20)-(5.24) with those reported by Busey and Mesmer (1978). Other data from measurements at elevated temperatures are also available (Busey and Mesmer, 1976 Becker and Bilal, 1985), and these data are in good agreement with the data of Busey and Mesmer (1978). Thus, protolysis constant data derived using Eqs. (5.17) and (5.20)-(5.24) also provide good predictions of the data of Busey and Mesmer (1976) and Becker and Bilal (1985). 

The temperature-dependent ion interaction parameters (Na, OH ) can be determined from the data listed in Table 5.13 and those listed for (H, C1 ) in Table 5.21. The values obtained are listed in Table 5.15. 

INTRODUCTION This data sheet summarizes properties of single crystal sodium chloride. 

MECHANICAL PROPERTIES, (298°K) Young s Modulus, (psi) 5. 8 x 10 Hardness, (Knoop) IJ  

Transmission Region, (External T ransmittance 10% with 2. 0 mm. thickness) 0. 21 - 26 ji  

Smakula, et al, Harshaw Optical Crystals, Harshaw Chemical Co., Cleveland, (1967). 

It is natural to enquire why different AX compounds should possess different structures, and, in particular, why CsCl, CsBr and Csl should have a structure different from that of the other alkali halides. We can answer this question if we consider fig. 3.07a, which represents a section through the caesium chloride unit cell on a vertical diagonal plane. The ions in this diagram are shown in their correct relative sizes for Cs+ and Cl-, and anions and cations are seen to be in contact at the points P. Now let us suppose that the cations are replaced by others of 

Thus the variation of the energy of the structure as a function of radius ratio will be of the form represented by curve (a) in fig. 3.08, with a discontinuity at this critical value of r+jr.  

Now let us consider the sodium chloride structure in a similar way. Fig. 3.09 represents a section through this structure on a plane parallel to one face of the cubic unit cell with the ions in their correct relative sizes for Na and Cl . The anions and cations are in contact at P. As before, let us now suppose that the sodium ions are replaced by others of 

We can continue this argument by considering the zincblende structure. In this case the critical radius ratio, corresponding to anion-anion contact, can be readily shown to be given by 

For large values of this radius ratio the energy of the structure is considerably greater than that of the sodium chloride arrangement. The variation of energy with radius ratio is therefore as represented by curve (c) in fig. 3.08, and it will be seen that the zincblende arrangement is the most stable of the three structures discussed for values of r+/r less than about 0 3. 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

Salt acts as a completely mobile plastic below 7600 m of overburden and at temperatures above 200°C (2). Under lesser conditions, salt domes can grow by viscous flow. Salt stmctures originate in horizontal salt beds at depths of 4000—6000 m or more beneath the earth s surface. The resulting salt dome or diapir is typically composed of relatively pure sodium chloride in a vertically elongated, roughly cylindrical, or inverted teardrop-shaped mass. 

Water is evaporated from purified brine using multiple-effect or vapor recompression evaporators (Figs. 3 and 4). Multiple-effect systems typically contain three or four forced-circulation evaporating vessels (Fig. 4) connected together in series. Steam from boilers suppHes the heat and is fed from one evaporator to the next to increase energy efficiency in the multiple-effect system. 

There are three important methods of salt isolation and purification brine solution, rock salt mining, and the open pan or grainer process. The percentages of these methods have not changed dramatically in the last few years and are 54% brine, 32% rock salt, and 14% grainer salt. 

In this method water is pumped into the salt deposit and the saturated salt solution is removed containing 26% salt, 73.5% water, and 0.5% impurities. Hydrogen sulfide is removed by aeration and oxidation with chlorine. Ca,  

and Fe are precipitated as the carbonates using soda ash. These are removed in a settling tank. The brine solution can be sold directly or it can be evaporated to give salt of 99.8% purity. Huge deposits of salt, some four miles in diameter and eight miles deep, can be mined by this method. 

Deep mines averaging 1000 ft are used to take the solid material directly from the deposit. Salt obtained by this method is 98.5-99.4% pure. Leading states producing rock salt and their percentages are Louisiana (30%), Texas (21%), Ohio (13%), New York (13%), and Michigan (10%). Over one fourth of the world s salt is produced in the U.S. 

Hot brine solution is held in an open pan approximately 4-6 m wide, 45-60 m long, and 60 cm deep at 96°C. Flat, pure sodium chloride crystals form on the surface and fall to the bottom. The crystals are raked to a centrifuge, separated from the brine, and dried. A purity of 99.98% is obtained. Grainer salt dissolves more readily and is preferred in some applications, such as the butter and cheese industries. It is more expensive because of energy use for the hot brine. Its cost can be as much as six times that of rock salt and 20 times that of brine. 

Solution Mining and Mechanical Evaporation. Bedded and domal salt deposits are solution-mined by drilling weUs into halite 

Rock salt is generally contaminated with calcium and magnesium sulfates and carbonates and with polyhalite (K2SO4 2CaS04 MgS04 2H2O). Crude brine, therefore, contains calcium, magnesium and sulfate ions. Purification of the brine is necessary before it is used in many processes, for example, the ammonia soda process (section 31.18), the electrolytic production of chlorine/caustic soda, and the production of purified salt. 

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S = Heat of sublimation of sodium D = Dissociation energy of chlorine / = Ionization energy of sodium = Electron affinity of chlorine Uq = Lattice energy of sodium chloride AHf = Heat of formation of sodium chloride. 

Also used to describe the oppositely charged ion balancing charge, e.g. chloride is the counter-ion to Na in sodium chloride. 

During production sodium chloride can deposit in layers on tubing walls after partial vaporization of the water due to the pressure drop between bottomhole and wellhead when these deposits become important large enough, the diameter of the well tubing is reduced. 

These water streams contain mainly dissolved salts ammonium chloride and sulfide, sodium chloride, traces of cyanide, phenols for water coming from catalytic and thermal cracking operations. 

The treated water containing sodium chloride, cyanides, phenols and traces of H2S and NH3 is recycled to the crude desalting unit and used as wash water for the hydrotreaters and FCC units. 

Fig. III-9. Representative plots of surface tension versus composition, (a) Isooctane-n-dodecane at 30°C 1 linear, 2 ideal, with a = 48.6. Isooctane-benzene at 30°C 3 ideal, with a = 35.4, 4 ideal-like with empirical a of 112, 5 unsymmetrical, with ai = 136 and U2 = 45. Isooctane-

The thickness of the equivalent layer of pure water t on the surface of a 3Af sodium chloride solution is about 1 A. Calculate the surface tension of this solution assuming that the surface tension of salt solutions varies linearly with concentration. Neglect activity coefficient effects. 

Refinements were made by Lennard-Jones, Taylor, and Dent [51-53], including an allowance for surface distortion. Their value of for (100) planes of sodium chloride at 0 K was 77 ergs/cm. Subsequently, Shuttleworth obtained a value of 155 ergs/cm [43]. 

It is important to evaluate the surface distortion associated with the assymetric field at the surface, a difficult task often simplified by assuming that distortion is limited to the direction normal to the plane [64, 6S]. Benson and co-workers [6S] calculated displacements for the first five planes in the (100) face of sodium chloride and found the distortion correction to of about 100 ergs/cm or about half of itself The displacements show a tendency toward ion pair formation, suggesting that lateral displacements to produce ion doublets should be considered [66] however, other calculations yielded much smaller displacements [67]. 

An indirect estimate of surface tension may be obtained from the change in lattice parameters of small crystals such as magnesium oxide and sodium chloride owing to surface tensional compression [121] however, these may represent nonequilibrium surface stress rather than surface tension [68]. Surface stresses may produce wrinkling in harder materials [122]. 

An excellent example of work of this type is given by the investigations of Benson and co-workers [127, 128]. They found, for example, a value of = 276 ergs/cm for sodium chloride. Accurate calorimetry is required since there is only a few calories per mole difference between the heats of solution of coarse and finely divided material. The surface area of the latter may be determined by means of the BET gas adsorption method (see Section XVII-5). 

Brunauer and co-workers [129, 130] found values of of 1310, 1180, and 386 ergs/cm for CaO, Ca(OH)2 and tobermorite (a calcium silicate hydrate). Jura and Garland [131] reported a value of 1040 ergs/cm for magnesium oxide. Patterson and coworkers [132] used fractionated sodium chloride particles prepared by a volatilization method to find that the surface contribution to the low-temperature heat capacity varied approximately in proportion to the area determined by gas adsorption. Questions of equilibrium arise in these and adsorption studies on finely divided surfaces as discussed in Section X-3. 

Most solid surfaces are marred by small cracks, and it appears clear that it is often because of the presence of such surface imperfections that observed tensile strengths fall below the theoretical ones. For sodium chloride, the theoretical tensile strength is about 200 kg/mm [136], while that calculated from the work of cohesion would be 40 kg/mm [137], and actual breaking stresses are a hundreth or a thousandth of this, depending on the surface condition and crystal size. Coating the salt crystals with a saturated solution, causing surface deposition of small crystals to occur, resulted in a much lower tensile strength but not if the solution contained some urea. 

The excess heat of solution of sample A of finely divided sodium chloride is 18 cal/g, and that of sample B is 12 cal/g. The area is estimated by making a microscopic count of the number of particles in a known weight of sample, and it is found that sample A contains 22 times more particles per gram than does sample B. Are the specific surface energies the same for the two samples If not, calculate their ratio. 

Substances in this category include Krypton, sodium chloride, and diamond, as examples, and it is not surprising that differences in detail as to frictional behavior do occur. The softer solids tend to obey Amontons law with /i values in the normal range of 0.5-1.0, provided they are not too near their melting points. Ionic crystals, such as sodium chloride, tend to show irreversible surface damage, in the form of cracks, owing to their brittleness, but still tend to obey Amontons law. This suggests that the area of contact is mainly determined by plastic flow rather than by elastic deformation. 

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.)...

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

The rocksalt stmcture is illustrated in figure Al.3.5. This stmcture represents one of the simplest compound stmctures. Numerous ionic crystals fonn in the rocksalt stmcture, such as sodium chloride (NaCl). The conventional unit cell of the rocksalt stmcture is cubic. There are eight atoms in the conventional cell. For the primitive unit cell, the lattice vectors are the same as FCC. The basis consists of two atoms one at the origin and one displaced by one-half the body diagonal of the conventional cell. 

Anisimov M A, Povodyrev A A, Sengers J V and Levelt-Sengers J M H 1997 Vapor-liquid equilibria, scaling and crossover in aqueous solutions of sodium chloride near the critical line Physica A 244 298... 

Koneshan S and Rasaiah J C 2000 Computer simulation studies of aqueous sodium chloride solutions at 298K and 683K J. Chem. Phys. 113 8125... 

Figure Bl.8.4. Two of the crystal structures first solved by W L Bragg. On the left is the stnicture of zincblende, ZnS. Each sulphur atom (large grey spheres) is surrounded by four zinc atoms (small black spheres) at the vertices of a regular tetrahedron, and each zinc atom is surrounded by four sulphur atoms. On the right is tire stnicture of sodium chloride. Each chlorine atom (grey spheres) is sunounded by six sodium atoms (black spheres) at the vertices of a regular octahedron, and each sodium atom is sunounded by six chlorine atoms.

Potassium chloride actually has the same stnicture as sodium chloride, but, because the atomic scattering factors of potassium and chlorine are almost equal, the reflections with the indices all odd are extremely weak, and could easily have been missed in the early experiments. The zincblende fonn of zinc sulphide, by contrast, has the same pattern of all odd and all even indices, but the pattern of intensities is different. This pattern is consistent with a model that again has zinc atoms at the comers and tlie face centres, but the sulphur positions are displaced by a quarter of tlie body diagonal from the zinc positions. 

Let us consider the formation of sodium chloride from its elements. An energy (enthalpy) diagram (called a Born-Haber cycle) for the reaction of sodium and chlorine is given in Figure 3.7. (As in the energy diagram for the formation of hydrogen chloride, an upward arrow represents an endothermic process and a downward arrow an exothermic process.)... 

A/ij the lattice energy of sodium chloride this is the heat liberated when one mole of crystalline sodium chloride is formed from one mole of gaseous sodium ions and one mole of chloride ions, the enthalpy of formation of sodium chloride. 

In view of your comments, discuss why sodium chloride is soluble in water. 

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