Phase behaviour quaternary system

Hirsch, E. Wittmann, J.C. Candan, F. Structure and viscometric behaviour of gel phases in quaternary systems containing anionic surfactants. J. Dispers. Sci. Technol. 1982, 5, 351-372. 

Hantzschel, D., Enders, S., Kahl, H., and Quitzsch, K. (1999), Phase behaviour of quaternary systems containing carbohydrate surf actants-water-oil-cosurf actant, Phys. Chem. Chem. Phys., 1,5703-5701. 

The crystallization behaviour of the glasses containing MgO is more difficult to describe. Unlike ternary systems, four component phase diagrams are properly represented by a regular tetrahedron with each apex representing 100% of each component. The crystallization path is therefore in three dimensions which is sometimes difficult to visualize. The method of representation chosen to describe the observed behaviour is as planes of constant MgO content in the regions of interest to this study. Figures 2, 3, and 4 are planes of the quaternary system at 5, 10 and 15 wt% levels respectively and have been compiled from various sources... 

In the preceding sections, the phase behaviour of rather simple ternary and quaternary non-ionic microemulsions have been discussed. However, the first microemulsion found by Schulman more than 50 years ago was made of water, benzene, hexanol and the ionic-surfactant potassium oleate [1, 3]. Winsor also used the ionic-surfactant sodium decylsulphate and the co-surfactant octanol to micro-emulsify water/sodium sulphate and petrol ether [2], In the last 30 years, in-depth studies on ionic microemulsions have been carried out [7, 8, 65, 66]. It toned out that nearly all ionic surfactants which contain one single hydrocarbon chain are too hydrophilic to build up microemulsions. Such systems can only be driven through the phase inversion if an electrolyte and a co-surfactant is added to the mixture (see below and Fig. 1.11). 

The variation of the phase behaviour as a function of the salinity is shown in Fig. 1.10(b) in the form of an (y)-section through the phase tetrahedron of the quaternary H20/NaCl-n-decane-A0T system at a = 0.50 and a constant temperature of T = 40° C. In order to compare the variation of the phase behaviour with temperature and salinity a rectangular representation is used also for the (y)-section through the phase tetrahedron. As can be seen, the phase boundaries also resemble the shape of a fish in this isothermal (y)-section. However, with increasing mass fraction of salt the phase sequence 2, 3, 2 is found which is inverse to the 2, 3, 2 sequence observed with increasing temperature. 

Ionic surfactants with only one alkyl chain are generally extremely hydrophilic so that strongly curved and thus almost empty micelles are formed in ternary water-oil-ionic surfactant mixtures. The addition of an electrolyte to these mixtures results in a decrease of the mean curvature of the amphiphilic film. However, this electrolyte addition does not suffice to drive the system through the phase inversion. Thus, a rather hydrophobic cosurfactant has to be added to invert the structure from oil-in-water to water-in-oil [7, 66]. In order to study these complex quinary mixtures of water/electrolyte (brine)-oil-ionic surfactant-non-ionic co-surfactant, brine is considered as one component. As was the case for the quaternary sugar surfactant microemulsions (see Fig. 1.9(a)) the phase behaviour of the pseudo-quaternary ionic system can now be represented in a phase tetrahedron if one keeps temperature and pressure constant. 

Dorfler et al [82] systematically studied the phase behaviour of quaternary systems, consisting of water, non-ionic surfactants, a co-surfactant and a hydrocarbon, with regard to possible applications in the textile-cleaning sector. As an example, Fig. 8.14 shows the... 

The set of the quaternary critical points comprises two asymptotic branches which meet at the cusp point - it defines the pentary critical point. These asymptotic branches are boundaries between systems with simple three-phase separation and systems with a more complex behaviour (two different three-phase regions, one of which may be unstable, and four-phase separation). 

Quaternary and higher systems have been investigated. In such cases, many phases may coexist. Indeed, since the phase behaviour is dependent on the molecular weight of the polymer, polydispersity itself results in a multicomponent system. 

Alany, R.G., Rades, T., Agatonovic-Kustin, S., Davies, N.M., and Tucker, LG. 2000 Effects of alcohols and diols on the phase behaviour of quaternary systems, Int. J. Pharm. 196 141-145. 

In order to illustrate the phase behaviour of microemulsions, it is most convenient to consider the systems with nonionic surfactants of the ethylene oxide type. These have been studied extensively by Shinoda and Kunieda and co-workers and by Kahlweit and Strey and co-workers (for more recent reviews, see, e.g. refs (9) and (10)). At low surfactant concentrations, there is a general sequence of phase equilibria, often referred to as Winsor equilibria (11). The equilibrium conditions for the microemulsion phase, L, changes from equilibrium with excess oil (Winsor I) to equilibrium with excess water (Winsor II), via a three-phase equilibrium with excess water and oil (Winsor III). For nonionics, this sequence occurs when increasing the temperature, while for quaternary or ternary systems, it can be observed with increasing salinity or cosurfactant-to-surfactant ratio. 

NaClO, or else in the two-phase system but with a quaternary ammonium (viz. AUquat) ion as a phase-transfer catalyst, overoxidation to the corresponding carboxylic acid is obtained (entry 4). Therefore, by proper choice of the experimental conditions, a synthetically useful distinction in products formation can be made for the oxidation of primary alcohols, even though we are far from a satisfactory understanding of the reason behind this different behaviour. In fact TEMPO, as a well-known inhibitor of free-radical processes is allegedly responsible for the lack of overoxidation of an aldehyde to carboxylic acid (entry 3) this notwithstanding, TEMPO is also present under those conditions where the overoxidation does occur (eutry 4). Moreover, a commou teuet is that the formation of the hydrated form of an aldehyde (in water solution) prevents further oxidation to the carboxylic acid however, both entries 3 and 4 refer to water-organic solutions, and their... 

These observations on the sulfuric acid catalyst arc full in line with the general thermodynamic behaviour of fused catalyst systems. The mctastablc solid in Figure 2 has to be replaced in this case by a cascade of the partly reduced vanadium ternary sulfates. The processes sketched above occur under thermodynamic control in a quaternary phase diagram, vanadium-oxygen-sulfur-alkali, as illustrated by the reversibility of the exsolution of the partly reduced vanadium compounds under suitable partial pressures of oxygen... 

The reverse situation is also true, for compositions on the 10% plane and in the primary phase field of spinel the secondary phase would be expected to comprise components of the base ternary systems. This behaviour was observed with the compositions studied in this investigation with the exceptions of those samples which crystallized anorthite only. The behaviour of these glasses can be explained in terms of the viscosity of the melt hindering further crystallization. This generalization of crystallization of quaternary systenns must be used with care especially when the precipitating phase may be a solid solution. 

The liquidus curve and the invariant temperatures are known to good accuracy. This result will be an aid for understanding the thermodynamic behaviour of the ternary and quaternary phases. It has been possible to calculate the temperature of the metastable melting point of CoSbj (1283K instead of 1210K for the peritectic decomposition of the 1 2 phase). One can observ e that these temperatures are not so far and it could explain the problems occuring in the fabrication of the materials as well as the lack of 1 3 compounds for iron and nickel systems. 

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