Single-salt solutions, applicability

Equilibrium constants calculated from the composition of saturated solutions are dependent on the accuracy of the thermodynamic model for the aqueous solution. The thermodynamics of single salt solutions of KC1 or KBr are very well known and have been modeled using the virial approach of Pitzer (13-15). The thermodynamics of aqueous mixtures of KC1 and KBr have also been well studied (16-17) and may be reliably modeled using the Pitzer equations. The Pitzer equations used here to calculate the solid phase equilibrium constants from the compositions of saturated aqueous solutions are given elsewhere (13-15, 18, 19). The Pitzer model parameters applicable to KCl-KBr-l O solutions are summarized in Table II. 

The range of applicability of the Setschenow Equation on the salt concentration in aqueous single-salt solutions varies with the system (gas plus an electrolyte) and is never confirmed clearly. Van Krevelen and Hoftijzer (4) showed the range to be up to 2 mol/L of ionic strength in all the systems, while Onda et al. (5) showed that the equation could be applied to the more concentrated solutions for some systems, such as up to 15 mol/L of ionic strength for carbon dioxide systems at the maximum. 

Nernst-Haskell The theory of dilute diffusion of salts is well developed and has been experimentally verified. For dilute solutions of a single salt, the well-known Nernst-Haskell equation (Reid et al.) is applicable ... 

This chapter considers five methods for calculating activity coefficients in multicomponent strong electrolyte mixtures. Generally, these methods are built upon the calculation of activity coefficients of single salt electrolyte solutions together with the application of certain "mixing rules". The methods considered in this chapter are ... 

When electrolytes are added to a solvent, they dissociate to a certain degree. It would appear that the solution contains at least three components solvent, anions, and cations. If the solution is to remain neutral in charge at each point, assuming the absence of any applied electric potential field, the anions and cations diffuse effectively as a single component, as with molecular diffusion. The diffusion of the anionic and cationic species in the solvent can thus be treated as a binary mixture. The theory of dilute diffusion of salts is well developed and has been experimentally verified. For dilute solutions of a single salt, the Nernst-Haskell equation is applicable ... 

Water Hyacinth. Water hyacinth (Eichornia crassipes Solms) has been killed by 0.1% solution of the alkanolamine salt of 2,4-D in Indonesia (54), or in the Philippines by the isopropyl ester in as low as 0.1% solutions (39). In the southern United States, 2,4-D has been widely used to kill this plant. This plant is of relatively minor importance in Puerto Rico. It tends to choke up river mouths and is removed to improve drainage. A single application of the isopropyl ester of 2,4-D has given excellent results on a small scale. 

The salt effect of single or mixed electrolytes on the solubility of a gas in water is of considerable industrial and theoretical interest. Methods to predict or correlate these effects have been presented by various workers and have been reviewed briefly (I). With the exception of a study by Clever and Reddy (2), previous investigations found no salt effect data on gas solubility in non-aqueous or mixed solvents. Clever and Reddy (2) observed the solubilities of helium and argon in methanol solutions of sodium iodide at 30° C and showed that the following Setschenow equation is not always applicable to such a system. 

An application has been found in which a system that exhibits an upper, or lower, critical consolute point, UCST or LCST, respectively, is utilized. At a temperature above or below this point, the system is one homogeneous liquid phase and below or above it, at suitable compositions, it splits into two immiscible liquids, between which a solute may distribute. Such a system is, for instance, the propylene carbonate - water one at 25°C the aqueous phase contains a mole fraction of 0.036 propylene carbonate and the organic phase a mole fraction of 0.34 of water. The UCST of the system is 73 °C (Murata, Yokoyama and Ikeda 1972), and above this temperature the system coalesces into a single liquid. Temperature cycling can be used in order to affect the distribution of the solutes e.g. alkaline earth metal salts or transition metal chelates with 2-thenoyl trifluoroacetone (Murata, Yokayama and Ikeda 1972). 

Liquid extraction systems consist either of pure solvents and mixtures, but may also contain additives. The application of single solvent or simple mixtures is well-known in classical physical extractions when using bulk organic chemicals (toluene, butanol, etc.) to extract a solute. Today, a new class of solvents is that of ionic liquids [10], which are low-melting organic salts where the cation is, for example, from... 

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