Experimental Studies Using Simple, Well-Defined Mixtures

6 EXPERIMENTAL STUDIES USING SIMPLE, WELL-DEFINED MIXTURES 

1 Chemicals with Different Target Organs and/or Different Modes of Action 

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The main emphasis is paid to the identification of the basic principles for combined actions and interactions of chemicals (Section 10.2), and to the current knowledge on effects of exposures to mixtures of industrial chemicals, including pesticides and environmental contaminants. Test strategies to assess combined actions and interactions of chemicals in mixtures (Section 10.3) as well as toxicological test methods (Section 10.4) are addressed, approaches used in the assessment of chemical mixtures are presented (Section 10.5), and examples of experimental studies using simple, well-defined mixtures are given (Section 10.6). 

This chapter is concerned with a few aspects of the theory of solutions that are either of fundamental character or useful in the study of aqueous solutions. We begin by generalizing some concepts and relationships from the theory of pure liquids and proceed with aspects that are specific to mixtures and solutions. The terms mixture and solution are used here almost synonymously. The latter is traditionally used when one component (the solute) is dissolved in the other (the solvent). Perhaps one of the most useful concepts in the theory of solution is the concept of ideal solutions. These were defined originally in terms of experimental observations, such as Raoult s or Henry s laws. We shall develop the theoretical background that led to such ideal behaviors. In section 6.7 we present the Kirkwood-Buff theory of solution—an important tool for the study of simple solutions as well as some aspects of aqueous solutions. The concept of solvation, though traditionally used in the context of extremely dilute solutions, is introduced beginning in section 6.13 and applied to any molecule (not necessarily a solute) in any fluid (not necessarily a solvent). This concept enters whenever we study processes such as chemical equilibrium, adsorption, allosteric effect, and so on, in the liquid state. 

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