Unidimensional formulation scan

When HLD = 0 three-phase behavior takes place because of the exact compensation of the effect of the different formulation variables expressed in Eqs. 4 and 5. hi practice, an unidimensional formulation scan is carried out to detect the occurrence of three-phase behavior. In such a scan, only one of the formulation variables (appearing in Eqs. 4 and 5) is changed, while all the others are held constant, as well as composition variables, i.e., surfactant concentration and water/oil ratio (WOR). 

The first technique is the so-called unidimensional formulation scan, in which a series of test tubes contain the same composition, i.e., the same amphiphile/oil/water proportions, but gradually changing formulation. For instance, the salinity of the aqueous phase is changed from one test tube to the next according to some progression (linear or geometric). It also could be the oil ACN or the surfactant tail length. 

Figure 8 Unidimensional formulation scan. Typically observed phase behavior for a system containing 2% anionic surfactant, 49% brine, and 49% alkane, versus the brine salinity.

Nevertheless, it is important to stries.s again that the PIT procedure was the first method to make use of the technique of unidimensional formulation scan, in which a physicochemical formulation variable (temperature) is changed conlin-... 

The investigation technique is the unidimensional formulation scan as in the phase behavior. studies discussed in the previous chapter. For the sake of simplicity, the scanned variable is often taken as the salinity for ionic surfactant systems, and as surfactant EON or temperature for nonionic systems, but it should be well understood that other formulation variables would produce exactly the. same effects. In the reasoning, the formulation will be referred to a.s SAD, the deviation from optimum formulation, whatever the variable used to produce the scan. 

Because of its basic phenomenon, the PIT is limited to ethoxylated nonionic siufac-tant systems, and its scale is sometimes insufficient to deal with highly ethoxylated detergents. Nevertheless, it is important to stress that the PIT procedure was the first method making use of the unidimensional formulation scan, in which a physico-chemical formulation variable (temperature) is changed continuously as all other formulation variables are held constant, until a very clear-cut situation arises that can be detected experimentally. The PIT determination is still performed today as such or in a slightly different version [51,112]. 

Figure 17 Aspect of test tube series in a unidimensional formulation scan at constant composition.

The stair shape of the inversion line may be determined easily by a relatively small number of unidimensional scans. First, mie or two formulation scans located from 40% to 60% water content allow one to locate the (formulation position of) horizontal branch of the inversion line. Then, a few composition f. scans located both below and above the horizontal branch allow one to locate the position of the vertical branches of the inversion line. Whenever there is no previous information on the system, the first composition. scans to be carried out may be located at two or three formulation distance" units from optimum formulation. These distances are evaluated from the correlation for optimum formulation. as discus.scd at the end of previous chapter. This dual-scan technique... 

The experimental technique used to find an optimum formulation, known as unidimensional scan, goes on as follows. Series of surfactani-oil-water systems are prepared in test tubes, all wnlh identical composition, and with the same formulation with the exception of the scanned variable, that is in general the aqueous phase. salinity for ionic systems, and the average number of ethylene oxide groups per molecule (EON) if the systems contain an cthoxylated nonionic surfactant mixture. 

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