Single-salt solutions, applicability aqueous

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. 

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). 

Simultaneous electrode reactions. Current efficiency If, as is frequently the case, several electrochemical reactions occur simultaneously at an electrode, Faraday s law will be found to hold only if the total number of equivalents which have entered into reaction arc used in the computation. Failure to include all the reactions at the electrode will thus result in an apparent deviation from the law. The ratio of the number of equivalents of a single electrode product to the total possible number computed by Faraday s law is called the current efficiency with respect to the electrochemical reaction in question. For instance, in the electrodeposition of zinc from an aqueous solution of one of its salts, hydrogen is always evolved. The ratio of the number of equivalents of zinc deposited to the total number of chemical equivalents (zinc and hydrogen) is the current efficiency of the deposition of zinc. Thus, as we have seen, a current efficiency of less than 100 per cent does not indicate a failure in the application of the law, but only that all the electrochemical reactions have not been included in the computation. 

To understand the chemistry that underlies coral reef formation, we must understand the concepts of aqueous equilibria. In this chapter we take a step toward understanding such complex solutions by looking first at further applications of acid—base equilibria. The idea is to consider not only solutions in which there is a single solute but also those containing a mixture of solutes. We then broaden our discussion to include two additional types of aqueous equilibria those involving slightly soluble salts and those involving the formation of metal complexes in solution. For the most part, the discussions and calculations in this chapter are an extension of those in Chapters 15 and 16. 

Abstract Natural and synthetic polyelectrolytes have acquired notable importance in recent years due to their increasing application in different areas. One of these is downstream process methods which include the recovery, separation, concentration and purification of target enzymes from their natural sources. Polyelectrolytes interact with proteins to form soluble or non-soluble complexes. The interaction is driven by experimental variables of media such as pH, protein isoelectrical value, polyelectrolyte pKa, ionic strength and the presence of salts. The concentration of polyelectrolytes necessary to precipitate a protein completely is of the order of 10 " - 10 % p/v. Precipitation of protein by PE is a novel technique integrating clarification, concentration and initial purification in a single step. This chapter presents some properties of aqueous solutions of natural and synthetic PE as a tool to use them in the protein downstream process. 

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