Oil and water mixture

In the latter the surfactant monolayer (in oil and water mixture) or bilayer (in water only) forms a periodic surface. A periodic surface is one that repeats itself under a unit translation in one, two, or three coordinate directions similarly to the periodic arrangement of atoms in regular crystals. It is still not clear, however, whether the transition between the bicontinuous microemulsion and the ordered bicontinuous cubic phases occurs in nature. When the volume fractions of oil and water are equal, one finds the cubic phases in a narrow window of surfactant concentration around 0.5 weight fraction. However, it is not known whether these phases are bicontinuous. No experimental evidence has been published that there exist bicontinuous cubic phases with the ordered surfactant monolayer, rather than bilayer, forming the periodic surface. 

K. Barthold, R. Baur, S. Crema, K. Oppenlaender, and J. Lasowski. Method of demulsifying crude oil and water mixtures with copolymers of acrylates or methacrylates and hydrophilic comonomers. Patent US 5472617, 1995. 

Emulsions are stable dispersions of two immiscible liquids. In the aluminum forming category this is usually an oil and water mixture. 

Accordingly, on a surface with a medium hydrophobic property, the interface boundary of oil and water mixture, for instance, will contact the wall surface forming a point between the interface and the surface. The relation between the surface tension and the two liquids can be expressed by Young s equation where y0ii-Water is the interface tension between oil and water, while Yofl-surface/Ywater-surface is the surface tension between the channel walls and the two phases [202]... 

A surfactant molecule is an amphiphile, which means it has a hydrophilic (water-soluble) moiety and a hydrophobic (water-insoluble) moiety separable by a mathematical surface. The hydrophobic tails of the most common surfactants are hydrocarbons. Fluorocarbon and perfluorocarbon tails are, however, not unusual. Because of the hydrophobic tail, a surfactant resists forming a molecular solution in water. The molecules will tend to migrate to any water-vapor interface available or, at sufficiently high concentration, the surfactant molecules will spontaneously aggregate into association colloids, i.e., into micelles or liquid crystals. Because of the hydrophilic head, a surfactant (with a hydrocarbon tail) will behave similarly when placed in oil or when put in solution with oil and water mixtures. Some common surfactants are sodium or potassium salts of long-chained fatty acids (soaps), sodium ethyl sulfates and sulfonates (detergents), alkyl polyethoxy alcohols, alkyl ammonium halides, and lecithins or phospholipids. 

Crude oil and water mixtures also formed stable emulsions when treated with the switchable amidine carbonate surfactant, and the emulsion could be broken by exposure to argon to give two separate layers. This shows the great potential... 

Agitation Control. Measures that reduce or eliminate agitation of an oil-and-water mixture will reduce emulsion stability or prevent emulsion formation. 

Oil molecules are nonpolar, so polar water molecules are not attracted to them. If you pour vegetable oil into a glass of water, the oil and the water separate into layers instead of forming a solution, as shown in Figure 10. You ve probably noticed the same thing about the oil-and-water mixtures that make up some salad dressings. The oil stays on the top. Oils generally dissolve better in solvents that have nonpolar molecules. 

The oil and water mixture has a residence time of 45-60 min in the tank with gentle agitation. 

A standard measure of lipid solubility is a physio-chemical parameter called logP. The logP of a solute is determined experimentally by adding the substance to a mixture of water and octanol. Water represents an aqueous, polar environment such as that surrounding each side of the lipid bilayer. Octanol represents a highly nonpolar solvent environment such as that found within the lipid bilayer. These two liquids are immiscible liquids, so they form a stable two-phase system much like an oil and water mixture. The solute is allowed to equilibrate between the two solvents, and the concentrations of the solute in both the octanol (Cq) and water (G y) phases are measured. The logP is then given by the relationship ... 

Determine whether or not each mixture is a solution. (a) sand and water mixture (b) oil and water mixture (c) salt and water mixture (d) sterling silver cup 24. Determine whether or not each mixture is a solution. (a) air (b) carbon dioxide and water mixture (c) a blueberry muffin (d) a brass buckle... 

Table 4.1. Qualitative effects of increasing the variables listed upon the phase behaviour of ethoxylated alcohol, non-polar oil and water mixtures...

The work of Kahlweit and Strey and their coworkers (27) thoroughly describes the patterns of phase behaviour of model monodisperse ethoxylated alcohols in non-polar oil and water mixtures (19, 27). Most importantly, T measures the optimal hydrophilic-lipophilic temperature for a particular combination of surfactant and oil, while y measures the minimum amount of surfactant required to mix the particular oil with water into a single microemulsion phase. 

Microemulsion formulations are not limited to the range of ethoxylated alcohol, ionic surfactant, non-polar oil and water mixtures discussed above. Indeed, other classes of surfactants and oils form microemulsions. Even non-aqueous microemulsions form upon the substitution of protic solvents for water. 

As noted above, raising the pressure in mixtures of ethoxylated alcohol, liquid alkane oil and water mixtures induces a 2-to-3-to-2 pattern, and thus pressure has the opposite effect of increasing temperature (27). Indeed, a fish -shaped phase diagram is observed at a fixed... 

Dobreva-Veleva, A. N., Kaler, E. W., Schubert, K.-V., Feiring, A. E. and Farnham, W. B., Phase behaviour and microemulsion formation in compressible perfluorinated monomer oil and water mixtures, Langmuir, 15, 4480 (1999). 

Example 2.2.3 An oil and water mixture may be separated by a hydrocyclone (Figure 2.2.2), which is essentially a truncated hollow cone with a cylindrical section at the top. The feed mixture enters tangentially in the cylindrical section through the feed nozzle. A water-rich heavy fraction leaves the unit as an underflow at the bottom of the device. The oil-rich light fraction leaves the unit at the top center opening. 

An "emulsion" is an oil and water mixture that has been subjected to shearing resulting in the division of oil and water phases into small droplets. Most emulsions encountered in the oil field are water droplets in an oil continuous phase and are referred to as "normal emulsions." Oil droplets in a water continuous phase are referred to as "reverse emulsions." Emulsions are discussed further in Chapter 2. 

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