Solutions of Gases in Liquids

Various flow calorimeters are available connnercially. Flow calorimeters have been used to measure heat capacities, enthalpies of mixing of liquids, enthalpy of solution of gases in liquids and reaction enthalpies. Detailed descriptions of a variety of flow calorimeters are given in Solution Calorimetry by Grolier [17], by Albert and Archer [18], by Ott and Womiald [H], by Simonson and Mesmer [24] and by Wadso [25]. 

Table 4. Diffusion Coefficients for Dilute Solutions of Gases in Liquids at 20°C ...

Solution of Gases in Liquids Certain gases will dissolve readily in hquids. In some cases in which the quantities are not large, this may be a practical storage procedure. Examples of gases that can be handled in this way are ammonia in water, acetylene in acetone, and hydrogen chloride in water. Whether or not this method is used depends mainly on whether the end use requires the anhydrous or the liquid state. Pressure may be either atmospheric or elevated. The... 

In the original equation of van Laar, the effective molar volume was assumed to be independent of composition this assumption implies zero volume-change of mixing at constant temperature and pressure. While this assumption is a good one for solutions of ordinary liquids at low pressures, it is poor for high-pressure solutions of gases in liquids which expand (dilate) sharply as the critical composition is approached. The dilated van Laar model therefore assumes that... 

Deviations from the laws of dilute solutions Solutions of gases in liquids Law of distribution... 

Pharmaceutical products can be classified as liquid solutions, disperse systems (e.g., emulsions, suspensions), semisolids (e.g., ointments), and solid dosage forms. Liquid solutions are homogeneous mixtures of one or more substances in pharmaceutical liquids. The understanding of the physicochemical properties of liquid solutions and processes to prepare the liquid solutions is an important step in preparing final liquid solution dosage forms. In this chapter, the solutions of gases in liquids, liquids in liquids, and solids in liquids, as well as colligative properties of solutions and their application to pharmacy, are discussed. Disperse systems will be discussed in Chapter 4. 

However, most solutions of gases in liquids do not behave ideally. Again, the activity coefficient can be considered as a measure of the deviation from ideality (Henry s law) ... 

Supersaturated solutions of liquids in liquids have only been realised m a few cases,2 but supersaturated solutions of gases in liquids are not uncommon. 

Comparing equations (2.19) and (2.20), it is clear that the Henry s law and Raoult s law expressions would become identical if k could be equated with 1 /p. Such an equating of terms is valid in the case of ideal solutions only, and in most solutions of gases in liquids, although k is constant, it is not equal to 1 /p. ... 

The solubility of a gas in a liquid depends on the pressure of the gas pushing down on the liquid. The higher the pressure, the more soluble is the gas. For solutions of gases in liquids, gas solubility decreases as temperature increases. That s why club soda fizzes more vigorously when it is warm. The dependence of gas solubility on temperature and pressure is important in a number of areas, as shown in Figure 13.26. 

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