Sodium chloride solubility

The binary sodium chloride-water system has been the object of many studies. As a result there is a wealth of published data for a wide range of temperatures. This data includes solubility, density, vapor pressure lowering and heat of solution measurements. Because of this availability of data and the straightforward strong electrolyte behavior of the system, sodium chloride has almost always been included as an example when illustrating activity coefficient modeling techniques. For this application, Meissner s method of activity coefficient calculation will be used. 

The equation describing the sodium chloride dissociation/precipitation is  

As this is a binary solution of a 1-1 electrolyte, the following relationships may be noted  

That is, the mean molal activity coefficient, Y+, equals the individual ionic activity ooeffioients. This results in the following equilibrium equation for sodium chloride solubility  

The solubility product of NaCl at 25 C may be calculated using values of Gibbs free energies which were presented by the National Bureau of Standards (26) and are tabulated in Appendix B  

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Calcium and/or Magnesium with Cation Exchanger (Insoluble) + Sodium Chloride (Soluble) = Sodium Cation Exchanger (Insoluble) + Calcium and/or Magnesium Chlorides (Soluble). 

Problem 11.47. Why is sodium chloride soluble in water but insoluble in hexane ... 

The suitability of the amines diisopropylamine (DiPA) and dimethylisopropylamine (DMiPA) as antisolvents for the crystallization of sodium chloride from its aqueous solution has been demonstrated. Both amines decreased the sodium chloride solubility substantially. The presence of a two liquid phase area offered the opportunity to separate the amines from the mother liquor after crystallization by a temperature increase. In the two liquid phase area the mutual solubilities of the water and the amines were low, so the separability was good. Continuous crystallization experiments were carried out at temperatures below the liquid-liquid equilibrium line in the single liquid phase area. The product consisted of cubic agglomerated NaCl crystals with maximum primary particle sizes of 10-70 pm. 

To be able to select a crystallization temperature in the single liquid phase region at a given amine fraction, the liquid-liquid equilibrium lines of the amine-water-NaClsat systems were determined. To establish to what extent an antisolvent reduces the sodium chloride solubility and to calculate the maximum obtainable magma densities during crystallization, sodium chloride solubilities in the amine-water mixtures were measured. Finally continuous crystallization experiments were carried out and the feasibility of an antisolvent recovery by a temperature increase was investigated. 

Sodium Chloride Solubilities in Amine-Water Mixtures. The sodium chloride solubilities were determined as a function of the amine concentration at the crystallization temperature in the single liquid phase region. The experiments were carried out in the equilibrium vessel as described in the previous section. The vessel was filled with a saturated sodium chloride solution. At the crystallization temperature a known amount of amine was added, resulting in the crystallization of sodium chloride. After a period of at least 60 minutes the stirring was stopped and liquid samples of the mixture were taken. Conductivity measurements showed that this period of time was sufficient to reach chemical equilibrium. The salt concentrations in the liquid samples were determined gravimetrically. 

Figure 6. The sodium chloride solubility as a function of the DMiPA concentration at 5 °C.

Since the sodium chloride solubility at an antisolvent fraction of 0.9 is practically zero, the binary DiPA-H20 liquid-liquid equilibrium data (see Figure 5) can be used to determine the aqueous and the organic phase compositions for the recovery of DiPA from a mixture with Xchpa = 0.9. 

The amines DiPA and DMiPA are suitable candidates for the antisolvent crystallization of sodium chloride. Both amines reduce the sodium chloride solubility substantially. At the antisolvent recovery conditions the mutual solubilities of the water and the amines were low, so the separability after crystallization was generally good. 

Irreversible thermodynamics molar volumes multicomponent systems non-aqueous osmotic coefficients oxidation-reduction potentials sodium chloride solubilities thermodynamics of mixing uni-polyvalent uni-univalent viscosity... 

To relate now the solution enthalpy to the slope of solubility curves, in Table 3.3 the AsHoo values are compiled for selected salts included in Figure 3.17. The steep increase of the solubility curve of potassium nitrate correlates with its comparatively high-positive solution enthalpy. Consistently, the weak (positive) temperature dependence of the sodium chloride solubility is expressed by a low (also positive) AsHoo value. Negative solution enthalpies occur for anhydrates of salts forming stable hydrates at room temperature (such as sodium sulfate and sodium carbonate) where hydration is connected vhth a strongly exothermal effect. 

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

The oxime is freely soluble in water and in most organic liquids. Recrystallise the crude dry product from a minimum of 60-80 petrol or (less suitably) cyclohexane for this purpose first determine approximately, by means of a small-scale test-tube experiment, the minimum proportion of the hot solvent required to dissolve the oxime from about 0-5 g. of the crude material. Then place the bulk of the crude product in a small (100 ml.) round-bottomed or conical flask fitted with a reflux water-condenser, add the required amount of the solvent and boil the mixture on a water-bath. Then turn out the gas, and quickly filter the hot mixture through a fluted filter-paper into a conical flask the sodium chloride remains on the filter, whilst the filtrate on cooling in ice-water deposits the acetoxime as colourless crystals. These, when filtered anddried (either by pressing between drying-paper or by placing in an atmospheric desiccator) have m.p. 60 . Acetoxime sublimes rather readily when exposed to the air, and rapidly when warmed or when placed in a vacuum. Hence the necessity for an atmospheric desiccator for drying purposes. 

The constant K is termed the distribution or partition coefficient. As a very rough approximation the distribution coefficient may be assumed equal to the ratio of the solubilities in the two solvents. Organic compounds are usually relatively more soluble in organic solvents than in water, hence they may be extracted from aqueous solutions. If electrolytes, e.g., sodium chloride, are added to the aqueous solution, the solubility of the organic substance is lowered, i.e., it will be salted out this will assist the extraction of the organic compound. 

In the isolation of organic compounds from aqueous solutions, use is frequently made of the fact that the solubility of many organic substances in water is considerably decreased by the presence of dissolved inorganic salts (sodium chloride, calcium chloride, ammonium sulphate, etc.). This is the so-called salting-out effect. A further advantage is that the solubility of partially miscible organic solvents, such as ether, is considerably less in the salt solution, thus reducing the loss of solvent in extractions. 

Cool 1 ml. of amylene in ice and add 1 ml. of cold, dilute sulphuric acid (2 acid 1 water), and shake gently until the mixture is homogeneous. Dilute with 2 ml. of water if an upper layer of the alcohol does not separate immediately, introduce a little sodium chloride into the mixture in order to decrease the solubility of the alcohol. Observe the odour. The unsaturated hydrocarbon is thus largely reconverted into the alcohol from which it may be prepared. 

Divide the saturated solution of n-butyl alcohol in water into three approximately equal parts. Treat these respectively with about 2-5 g. of sodium chloride, potassium carbonate and sodium hydroxide, and shake each until the soli have dissolved. Observe the effect of these compounds upon the solubility of n-butanol in water. These results illustrate the phenomenon of salting out of organic compounds, t.e., the decrease of solubility of organic compounds in water when the solution is saturated with an inorganic compound. The alcohol layer which separates is actually a saturated solution of water in n-butyl alcohol. 

Because of the great solubility of sulphonic acids in water and the consequent difficulty in crystallisation, the free sulphonic adds are not usually isolated but are converted directly into the sodium salts. The simplest procedure is partly to neutralise the reaction mixture (say, with solid sodium bicarbonate) and then to pour it into water and add excess of sodium chloride. An equilibrium is set up, for example ... 

The high sodium ion concentration results in facile crystallisation of the sodium salt. This process of salting out with common salt may be used for recrystallisation, but sodium benzenesulphonate (and salts of other acids of comparable molecular weight) is so very soluble in water that the solution must be almost saturated with sodium chloride and consequently the product is likely to be contaminated with it. In such a case a pure product may be obtained by crystallisation from, or Soxhlet extraction with, absolute alcohol the sul-phonate is slightly soluble but the inorganic salts are almost insoluble. Very small amounts of sulphones are formed as by-products, but since these are insoluble in water, they separate when the reaction mixture is poured into water ... 

In general, benzoylation of aromatic amines finds less application than acetylation in preparative work, but the process is often employed for the identification and characterisation of aromatic amines (and also of hydroxy compounds). Benzoyl chloride (Section IV, 185) is the reagent commonly used. This reagent is so slowly hydrolysed by water that benzoylation can be carried out in an aqueous medium. In the Schotten-Baumann method of benzoylation the amino compound or its salt is dissolved or suspended in a slight excess of 8-15 per cent, sodium hydroxide solution, a small excess (about 10-15 per cent, more than the theoretical quantity) of benzoyl chloride is then added and the mixture vigorously shaken in a stoppered vessel (or else the mixture is stirred mechanically). Benzoylation proceeds smoothly and the sparingly soluble benzoyl derivative usually separates as a solid. The sodium hydroxide hydrolyses the excess of benzoyl chloride, yielding sodium benzoate and sodium chloride, which remain in solution ... 

Another teat, which indicates the reactivity of the halogen atom (chlorine and bromine), is based upon the fact that sodium chloride and sodium bromide are sparingly soluble in pure acetone ... 

SODIUMCOMPOUNDS - SODIUMHALIDES - SODIUM CHLORIDE] (Vol22) -solubility diagram for [CRYSTALLIZATION] (Vol 7)... 

Mercuric Sulfate. Mercuric s Af2iX.e.[7783-35-9] HgSO, is a colorless compound soluble ia acidic solutions, but decomposed by water to form the yellow water-iasoluble basic sulfate, HgSO 2HgO. Mercuric sulfate is prepared by reaction of a freshly prepared and washed wet filter cake of yellow mercuric oxide with sulfuric acid ia glass or glass-lined vessels. The product is used as a catalyst and with sodium chloride as an extractant of gold and silver from roasted pyrites. 

Four minerals are the principal commercial sources of potash (Table 2). In all ores, sodium chloride is the principal soluble contaminant. Extraneous water-iasoluble material, eg, clay and siUca, is a significant contaminant ia some of the evaporates being mined from underground deposits. Some European potassium ores contain relatively large amounts of the mineral kieserite, MgS04-H2 0. It is recovered for captive use to produce potassium sulfate compounds or is marketed ia relatively pure form as a water-soluble magnesium fertilizer. 

Fractional crystallisation is based on favorable solubiUty relationships. Potassium chloride is much more soluble at elevated temperatures than at ambient temperatures in solutions that are saturated with sodium and potassium chlorides. Sodium chloride is slightly less soluble at elevated temperatures than at ambient temperatures in solutions that are saturated with KCl and NaCl. Working process temperatures are usually 30—110°C. The system,... 

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