Sodium sulfate/water diagram

Real crystals are often not in the equilibrium state in aqueous surfactant mixtures. Sometimes, this is true simply because the equilibrium crystal is disordered. In other cases, a nonequilibrium situation exists because the crystal present is not the equilibrium coexisting phase [48]. If a crystal that is not the equilibrium phase is mixed with water, the solubility initially observed will typically be higher than the equilibrium solubility. An excellent illustration of this behavior is found in the sodium sulfate—water diagram (Fig. 5), where the equilibrium coexisting crystal below 32.4°C is the decahydrate (X Wio). A metastable heptahydrate crystal (X W,) also exists in this system, which can be seen from the diagram to be significantly more soluble and have a lower peritectic temperature (23.7 C) than the equilibrium decahydrate. 

Figure 16.3. Enthalpy-composition diagrams of some salt solutions. Several other diagrams are in the compilation of Landolt-Bomstein, IV 4b, 1972, pp. 188-224. (a) sodium sulfate/water (b) magnesium sulfate/water (after Chemical Engineers Handbook, 1963 edition, McGraw-Hill, New York) (c) sodium carbonate/water.

The phase diagram of sodium dodecyl sulfate-water is representative of many ionic systems (Figure 3.7) [5], In Figure 3.7 Liquid is the aqueous micellar phase Ha is the hexagonal lyotropic liquid crystal, sometimes called the middle phase and La is the lamellar lyotropic liquid crystal, sometimes called the neat phase. On the surfactant-rich side, several hydrated solid phases are present. 

Figure 11.2-4 shows typical solubility diagrams for solutions of various salts in water. The curve for salt (NaCI) is nearly vertical, which indicates little effect of temperature ou solubility. The sodium sulfate curve shows reverse solubility as temperature increases thus, sodium solfate has a tendency to coat heat-exchanger surfaces where heat is added to saturated solutions of this system. 

The process of making water-insoluble PVA fiber was reported in 1939 [9] and is explained here briefly. An aqueous solution of PVA is spun by a wet process using a concentrated aqueous solution of sodium sulfate as a coagulation bath. The spinning proceeds smoothly, but the fiber cannot be washed with water because it is water soluble. When PVA fiber is stretched, it is not soluble in water at room temperature. Its x-ray diagram shows clearly that the fiber is partially crystalline, similar to highly stretched dry rubber. When stretched PVA is relaxed, it is again water soluble. 

Fig. 6.6 Phase diagram of the sodium dodecyl sulfate-water system near the Krafft point Tk. (From Ref. 86. Reproduced by permission of Pergamon Press.)...

Phase diagrams of the sodium perfluorodecanoate-sodium decyl sulfate-water system have been constructed from the dependence of solubility and cmc on temperature [202]. Two kinds of micelles were found a fluorocarbon-rich mixed micelle and a hydrocarbon-rich mixed micelle. 

The Diels-Alder reaction of methyl methacrylate with cyclopentadiene was studied [72] with solutions from three different regions of the pseudophase diagram for toluene, water and 2-propanol, in the absence and in the presence of surfactant [sodium dodecyl sulfate (SDS) and hexadecyltrimethylammonium bromide (HTAB)]. The composition of the three solutions (Table 6.11) corresponds to a W/O-fiE (A), a solution of small aggregates (B) and a normal ternary solution (C). The diastereoselectivity was practically constant in the absence and in the presence of surfactant a slight increase of endo adduct was observed in the C medium in the presence of surfactant. This suggests that the reaction probably occurs in the interphase and that the transition state has a similar environment in all three media. 

Figure 8.7 shows the ternary phase diagram for water, hexanoic acid, and sodium dodecyl sulfate at 25 °C. Seven different areas are shown in the figure, which has been used to describe the solubilization of polar dirt by surfactant solutions in detergency applications. The following comments refer to these seven different regions and explain the labeling used in Figure 8.7 ...

FIG. 8.7 Ternary phase diagram for water (W), hexanoic acid (A), sodium dodecyl sulfate (S) at 25°C. See text for a description of the various regions. (Redrawn, with permission, from A. S. C. Lawrence, Chem. Ind., 44, 1764 (1961).)... 

Figure 16.2. Some phase diagrams, (a) The water end of the system potassium chloride and water, (b) The water end of the system sodium chloride and water, (c) The water end of the system magnesium sulfate and water the heptahydrate goes to the mono at 150°C, and to anhydrous at 200°C. (d) /3-methylnaphthalene and /S-chloronaphthalene form solid solutions, (e) Mixtures of formamide and pyridine form a simple eutectic, (f) These mixtures form binary eutectics at the indicated temperatures and a ternary eutectic at mol fractions 0.392 dibenzyl, 0.338 diphenyl, and 0.27 naphthalene.

The HDC flow system used is very similar to many of today s liquid chromatograph units. A schematic diagram of the HDC apparatus is shown in Figure 1. The eluant consists of a solution of sodium lauryl sulfate at concentrations ranging from 1 to lOmM (millimolar) in distilled deionized water. A trace of formaldehyde is added to the eluant to avoid bacterial growth in the column. Prior to use, the... 

The calculated results in the absence of electrolyte will be now compared with the experimental results obtained regarding a lamellar lyotropic liquid crystal SDS (sodium dodecyl sulfate)/pentanol/water/dodecane swollen in a mixture of dodecane and pentanol.24 The weight fraction water/surfactant was 1.552 from the dilution line in the phase diagram, we calculated that the initial concentration of pentanol in the oil-free system was 29 wt % and the concentration of pentanol in the dodecane-based diluant was 8 wt %. The experimental values for the repeat distance were obtained from the X-ray diffraction spectrum (Figure 2 in ref 24) for various dodecane concentrations. 

Follow this procedure Mix cup of water with 1 teaspoonful of sucrose. Mix cup of water with 1 teaspoonful of sodium chloride. Mix cup of warm water with 1 teaspoonful of copper sulfate crystals. Note the color of the third solution. Now pour all three solutions into the pyrex flask. Arrange the apparatus as the diagram shows. You will have to bend the glass tubing in two places. Put some ice cubes into the pot or bowl and add some water. This will keep the temperature at a more constant level. Then put the pint jar into the bowl. Place the alcohol burner under the flask, and bring the mixture to a slow boil. 

Figure 12.28 Orientation diagram of shear rate y versus lamellar layer thickness d, whieh is controlled by the surfactant concentration, for water and sodium dodecyl-sulfate in the mass ratio 1.55 to 1 mixed with a solution of dodecane and pentanol. At low shear rates (region 1) defect-ridden lamellae appear, predominantly oriented parallel to the shearing surfaces (orientation c ). At intermediate shear rates (region 2), onions form, while at high shear rates (region 3), lamellae in orientation c again form, but with few or no defects. (From Roux et al. 1993, with permission from EDP Sciences.)...

In Figure 4.2, the concentration-temperature diagram is shown for sodium dodecyl sulfate (SDS) in water. The solid line denotes the solnbility limit the dashed line is the solubility that is expected based on extrapolation of the behavior at low temperatures. The rate of solubility increases with temperatnre changes abruptly at about 10°C, which is known as the Krafft point. Below this temperatnre, no micelles are present and the solid surfactant, in which the hydrocarbon chains are rather rigid, is formed at the solubility limit. However, above the Krafft point, micelles whose hydrocarbon chains are much more fiexible form at con-centrahons above the dashed line, which represents the CMC. At much higher concentrahons (not shown), the solubility limit is ultimately reached and a liquid crystalline phase also having fiexible chains separates. Snch phases are discussed in Sechon 4. 

Interfacial tension has been deduced from the spectrum of the light scattered by the interface. The results are relative to water-toluene-sodium dodecyl sulfate (SDS)-butanol mixtures either in the two phase, or in the three phase region of the phase diagram. Values down to 10 dynes/cm have been measured. Measurements down to 10 - 10 6 dynes/cm are expected to be achievable with this technique. 

The samples were made using toluene as oil and a mixture of sodium dodecyl sulfate (SDS) and butanol as emulsifier. The phase diagram of this system was extensively studied by Lalanne et al. (8). The composition of samples is indicated in Table 1. Their densities, viscosities and refractive indices are reported in Table 2. The three-phase samples were obtained by adding salt into water (the limits of the three-phase domain for the samples of Table 1 were 5.8% - 7.8% of salt in water). 

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