Multicomponent salt solutions

For multicomponent salt solutions, the integration of equation (13) can be quite horrendous and Meissner and Kusik (8 ) proposed a simplication which is exact for solutions containing... 

The density p of a multicomponent salt solution can then be calculated from... 

The A parameter in this equation can be calculated theoretically.The B parameter is determined from experimental data. 17 is the viscosity of the solution and rjo is the viscosity of the pure solvent. The B parameter is usually considered additive and an approximation of the viscosity of a multicomponent salt solution can be obtained by adding the contributions from all ions. 

In recent studies, Friberg and co-workers (J, 2) showed that the 21 carbon dicarboxylic acid 5(6)-carboxyl-4-hexyl-2-cyclohexene-1-yl octanoic acid (C21-DA, see Figure 1) exhibited hydrotropic or solubilizing properties in the multicomponent system(s) sodium octanoate (decanoate)/n-octanol/C2i-DA aqueous disodium salt solutions. Hydrotropic action was observed in dilute solutions even at concentrations below the critical micelle concentration (CMC) of the alkanoate. Such action was also observed in concentrates containing pure nonionic and anionic surfactants and C21-DA salt. The function of the hydrotrope was to retard formation of a more ordered structure or mesophase (liquid crystalline phase). 

When multicomponent alkoxide solutions, or a single alkoxide and a soluble inorganic salt, are mixed, a multicomponent alkoxide may result. In this way, such complex oxides such as the YBCO superconductor (cf. Section 6.1.2.4) can be formed. Sol-gel processing can also be used to coat fibers for composites and to form ceramics with very fine pore sizes called xerogels. A xerogel commonly contains 50-70% porosity, a pore size of 1-50 nm, and a specific surface area exceeding 100 m /g. 

It should be noted that the sol-gel process is particularly attractive for the synthesis of multicomponent particles with binary or ternary compositions using double alkoxides (two metals in one molecule) or mixed alkoxides (with mixed metaloxane bonds between two metals). Atomic homogeneity is not easily achieved by coprecipitating colloidal hydroxides from a mixture of salt solutions, since it is difficult to constmct double metaloxane bonds from metal salt. Hybrid... 

A second example is provided by a semiempirical correlation for multi-component activity coefficients in aqueous electrolyte solutions shown in Fig. 2. This correlation, developed by Fritz Meissner at MIT [3], presents a method for scale-up activity-coefficient data for single-salt solutions, which are plentiful, are used to predict activity coefficients for multisalt solutions for which experimental data are rare. The scale-up is guided by an extended Debye-Hilckel theory, but essentially it is based on enlightened empiricism. Meissner s method provides useful estimates of thermodynamic properties needed for process design of multieffect evaporators to produce salts from multicomponent brines. It will be many years before sophisticated statistical mechanical techniques can perform a similar scale-up calculation. Until then, correlations such as Meissner s will be required in a conventional industry that produces vast amounts of inexpensive commodity chemicals. 

Very recently Geus and co-workers [44, 45] have applied another method based on chemical complexes. This is the complex cyanide method to prepare both monocomponent (Fe or Co) and multicomponent Fischer-Tropsch catalysts. A large range of insoluble complex cyanides are known in which many metals can be combined, e.g. iron(n) hexacyanide and iron(m) hexacyanide can be combined with iron ions, but also with nickel, cobalt, copper, and zinc ions. Soluble complex ions of molybdenum(iv) which can produce insoluble complexes with metal cations are also known. Deposition precipitation (Section A.2.2.1.5) can be performed by injection of a solution of a soluble cyanide complex of one of the desired metals into a suspension of a suitable support in a solution of a simple salt of the other desired metal. By adjusting the cation composition of the simple salt solution, with a same cyanide, it is possible to adjust the composition of the precursor from a monometallic oxide (the case when the metallic cation is identical to that contained in the complex) to oxides containing one or several foreign elements. 

Biological systems are, by definition, multicomponent systems. One should keep in mind the difficulties of constructing molecular level pictures that satisfactorily describe systems such as a protein in a reverse micelle or a protein in a concentrated aqueous salt solution, which are certainly much simpler than anhydrobiotic organisms, for example. It is not clear to what extent the water of the hydration shell can be replaced by a third component (e.g., lipid) or what effect such replacement has on protein or enzyme properties. 

Duer W. C., Leung W. H., Oglesby G. B., and Millero F. J. (1976) Seawater. A test for multicomponent electrolyte solution theories II. Enthalpy of mixing and dilution of the major sea salts. J. Solut. Chem. 5, 509—528. 

Our results regarding the gas solubility in binary mixed solvents are presented in papers (3.1-3.2, 3.4). The new expression for the composition dependence of Hemy s constant in mixed solvents, which requires only the solubihties in the pure solvents (3.1), and the new analysis of the gas solubihty in aqueous salt solutions, which provides new criteria for salting-in or salting-out, should be noted (3.2). In addition, a method for predicting Henry s constant in multicomponent (ternary and higher) mixed solvents was developed and compared with experiment (3.5). Our method also aUows one to predict the solubility of a binary (or multicomponent) gas mixture in individual solvents (3.4). 

Within the last 30 years, micro emulsions have also become increasingly significant in industry. Besides their application in the enhanced oil recovery (see Section 10.2 in Chapter 10), they are used in cosmetics and pharmaceuticals (see Chapter 8), washing processes (see Section 10.3 in Chapter 10), chemical reactions (nano-particle synthesis (see Chapter 6)), polymerisations (see Chapter 7) and catalytic reactions (see Chapter 5). In practical applications, micro emulsions are usually multicomponent mixtures for which formulation rules had to be found (see Chapter 3). Salt solutions and other polar solvents or monomers can be used as hydrophilic component. The hydrophobic component, usually referred to as oil, may be an alkane, a triglyceride, a supercritical fluid, a monomer or a mixture thereof. Industrially used amphiphiles include soaps as well as medium-chained alcohols and amphiphilic polymers, respectively, which serve as co-surfactant. 

Bromley felt that treating a multicomponent solution as a single complex salt solution would be the simplest approach towards calculating the activity coefficients of electrolytes in solution. The Fj terms would then be based on the ionic interactions of this "complex salt". Using the convention that odd number subscripts denote cations and even number subscripts indicate anions, he proposed for a cation ... 

Theoretical relationships for activity coefficients. The Setschenow equation is used to calculate the activity coefficients of aqueous molecular species in salt solutions. The Pitzer based methods may be used for binary or multicomponent solution activity coefflcient calculations for all species in the solution. 

The left hand side of the equation is the term that was found using the binary solution data. The activity coefficient Y was set equal to the activity coefficient for HCl in a salt solution of equal ionio strength using the assumptions detailed earlier. Therefore the only unknown in equation (7.9) is the molality of the hydrogen ion in the multicomponent solution ... 

The vapor pressure data presented in the literature is often the partial pressure of the nonelectrolyte in binary solution and the partial pressures in salt solutions of varying concentrations. The relationship between the partial vapor pressures of a nonelectrolyte in binary solution and in multicomponent solutions is described ... 

In addition to their unusual amino acid content, halophilic proteins need high salt concentrations for maintaining their structure. The volume of halophilic proteins must be measured in these extreme multicomponent solutions. In the case of halophiles, removal of salt would lead to protein denaturation. Some examples for halophilic proteins in concentrated salt solutions are given in Table 11 cf. the values for halophilic malate dehydrogenase and halophilic glutamate dehydrogenase. 

In crystallization from solution, as in the manufacture of salt from brine, the liquid phase is multicomponent, having one or more solvents and one or more solutes. Here both temperature and concentration are determining factors. 

Many electrochemical devices and plants (chemical power sources, electrolyzers, and others) contain electrolytes which are melts of various metal halides (particularly chlorides), also nitrates, carbonates, and certain other salts with melting points between 150 and 1500°C. The salt melts can be single- (neat) or multicomponent (i.e., consist of mixtures of several salts, for their lower melting points in the eutectic region). Melts are highly valuable as electrolytes, since processes can be realized in them at high temperatures that would be too slow at ordinary temperatures or which yield products that are unstable in aqueous solutions (e.g., electrolytic production of the alkali metals). 

Direct Chemical or Electrochemical Deposition of the Disperse Catalyst This method of direct deposition from a solution of its salt on a suitable conducting substrate is simpler and more practical than the preparation of electrodes from the hnished powders. It has the merit of being able to provide better contact between the catalyst and substrate, and multicomponent metal catalysts can be deposited from a solution containing a mixture of salts of several metals. 

The typical system for which the equilibrium composition is desired however does not contain a single salt in solution but more usually the equivalent of several salts in solution. In addition, the activities required in equilibrium expressions arising from the law of mass action are single ion activities or in general, single ion activity coefficients. And, we are interested in the ionic activity coefficeint of each species in a multicomponent system. 

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