Incremental packing effect

Cooling in the crossflow mode requires an incremental trial and error technique, best suited to computer analysis. The tower characteristic KaV/L can then be plotted against varying L/G ratios, and this gives a measure of the ability of the packing to effect the transfer (Figure 34.18). 

Different surfactants are usually characterised by the solubility behaviour of their hydrophilic and hydrophobic molecule fraction in polar solvents, expressed by the HLB-value (hydrophilic-lipophilic-balance) of the surfactant. The HLB-value of a specific surfactant is often listed by the producer or can be easily calculated from listed increments [67]. If the water in a microemulsion contains electrolytes, the solubility of the surfactant in the water changes. It can be increased or decreased, depending on the kind of electrolyte [68,69]. The effect of electrolytes is explained by the HSAB principle (hard-soft-acid-base). For example, salts of hard acids and hard bases reduce the solubility of the surfactant in water. The solubility is increased by salts of soft acids and hard bases or by salts of hard acids and soft bases. Correspondingly, the solubility of the surfactant in water is increased by sodium alkyl sulfonates and decreased by sodium chloride or sodium sulfate. In the meantime, the physical interactions of the surfactant molecules and other components in microemulsions is well understood and the HSAB-principle was verified. The salts in water mainly influence the curvature of the surfactant film in a microemulsion. The curvature of the surfactant film can be expressed, analogous to the HLB-value, by the packing parameter Sp. The packing parameter is the ratio between the hydrophilic and lipophilic surfactant molecule part [70] ... 

Because of steric factors there is not a simple relationship between AG or AH or TAS and the ionic radius . There is then no simple explanation of such observations as tetrad effects, see below, since some such breaks could come about in an apparent series of ion size changes of equal increment. Tetrad breaks may occur at the expected place following ionic size differentials but may also occur elsewhere through the sensitivity of packing problems. 

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