Optimum salinity, definition

Experimental data suggest that the optimum salinity varies linearly with the cosolvent concentration. Therefore, p7 can be estimated from the slope of the straight line of normalized optimnm salinity (C5i,op/C i,op) versns f in the case without divalent cations, as schematically shown in Figure 7.20. To obtain the effect of cosolvent on the shift in optimum salinity, P, we need to measure the volume fraction diagram for at least two different cosolvent concentrations and must know C i op. According to the definition, ff is defined as V7/(V7 + V3). 

By the preceding definition, will be independent of WOR and depend only on salinity, as we would expect. According to Eq. 7.74, when Si (i.e., WOR) increases, C31, the surfactant concentration in the water phase, will decrease so that the total amount of surfactant in the water phase, V31, is independent of WOR but dependent on the salinity. At the optimum salinity, V32 = V31, the surfactant has equal partition in the aqueous and oleic phases. However, Eq. 7.74 has not been tested using experimental data. 

By definition, HLD = 0 at optimum formulation, and away from it, it is the expression of the relative surfactant affinity difference from it. Since the partition coefficient may be measured with a proper analytical technique, its variation with respect to formulation variables such as surfactant EON, oil ACN, water salinity S etc. may be determined. Such studies have been carried extensively with polyethoxylated surfactants and have shown that HLD dependence on the formulation variables has the same expression than the correlation for three-phase behaviour [35, 36]. It holds... 

As seen in Fig. 20, the solubilization parameter curves cross over at exactly the same formulation (here salinity) where the interfacial tension curves do it, which is expected if the Hu relationship strictly applies. At this point, which is by definition the optimum formulation of the scan, the microemulsion is solubilizing the same amoimt of oil and water (as V = Vw) and its representative point on a SOW diagram is exactly at the same distance from the W and O vertices. As seen in Fig. 20, the solubilization increases from both sides when the formulation tends to the optimum one. The value of the solubilization parameter at optimum is generally referred to as SP (the maximum of the minimum of the Vq/Vs and Vw/Vs ratios that is attained at Vq/Vs = It is worth noting that SP ... 

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