Surfactant sodium decyl sulphate

In reverse, the surfactant precipitates from solution as a hydrated crystal at temperatures below 7k, rather than forming micelles. For this reason, below about 20 °C, the micelles precipitate from solution and (being less dense than water) accumulate on the surface of the washing bowl. We say the water and micelle phases are immiscible. The oils re-enter solution when the water is re-heated above the Krafft point, causing the oily scum to peptize. The way the micelle s solubility depends on temperature is depicted in Figure 10.14, which shows a graph of [sodium decyl sulphate] in water (as y ) against temperature (as V). 

Figure 10.14 Graph of [surfactant] (as y ) against T (as V) for sodium decyl sulphate in water. The Krafft temperature is determined as the intersection between the solubility and CMC curves, yielding a /K of about 22 °C. At lower temperatures, the micelles convert to form hydrated crystals, which we might call scum (Reproduced by permission of Wiley Interscience, from The Colloidal Domain by D. Fennell Evans and Hakan Wennerstrom)...

The purpose of this paper is to give a brief summary of an Investigation which has been carried out into the aqueous-phase polymerisation of butadiene initiated by cobalt(III) acetylacetonate In the presence of surfactants such as sodium dodecylbenzene-sulphonate and sodium decyl sulphate. It is Intended that fuller details of the investigation will be published elsewhere in due course. 

In fact, experimental surface tensions of mixtures of sodium decyl sulphate SDeS (component 1) and sodium dodecyl sulphate SDS (component 2) are described satisfactorily by Eq. (2.48) whereas the application of Eq. (2.51) leads to large differences between theory and experiment [67]. The best agreement between experimental and theoretical values of n was received by using the Frumkin analogue of Eqs. (2.48)-(2.50) with ai=0.7, a2=0.85 and ai2=(ai+a2)/2=0.77. Similarly, mixtures of decyl ammonium chloride and dodecyl ammonium chloride were very well described by these equations with ai=1.2, a2=1.56 and ai2=(ai+a2)/2=1.38 [16]. The latter system also reveals a reverse salting-out effect as an excess of inorganic counterions in the solution increases the adsorption activity of an ionic surfactant, by the same token such an excess in the surface decreases the adsorption activity. As a result, the effect of a second ionic surfactant with a common counterion on the surface pressure is smaller than it would have been according to the additivity rule for non-ionic surfactants expressed in Eq. (2.51). 

At a particular temperature, the solubility becomes equal to the c.m.c., i.e. the solubility curve intersects the c.m.c. and this temperature is referred to as the KrafFt temperature of the surfactant, which for sodium decyl sulphate is 22 °C. At the KrafFt temperature an equilibrium exists between solid hydrated surfactant, micelles and monomers (i.e. the KrafFt point is a triple-point ). Since the KrafFt boundary represents the region below which crystals separate, the energy of the... 

Figure 9.4(a) Zeta potential as a function of the logarithm of the concentration of anionic surfactants adsorbed on to polystyrene latex sodium tetradecyl sulphate, NaDS, and O sodium decyl sulphate. The CMC for NaDS in water is shown by the arrow, (b) Shows... 

Surfactants Ionic, anionic (e.g., sodium dodecyl sulphate, Cj2H250S03 Na ), cationic (e.g., cetyl trimethyl ammonium chloride, Ci,H33-N+(CH3)3C1-), zwitterionic [e.g., 3-dimethyldodecylamine propane sulphonate (betaine CJ2H25-N" (CH3)2-CH2-CH2-CH2-S03)], nonionic, alcohol ethoxylates C H2 +i-0-(CH2-CH2-0) -H, alkyl phenol ethoxylates C H2 +i-CgH4-0-(CH2-CH2-0) -H, amine oxides (e.g., decyl dimethyl amine oxide, C10H21-N ( 113)2 0), and amine ethoxylates. 

Moreover, adsorption isotherms, or equations of state, represent the basis for the evaluation of adsorption kinetics and rheological properties of adsorption layers. Exact equilibrium values of surface or interfacial tensions are necessary to determine adsorption isotherms. For surfactants of low surface activity (for example, sodium octyl or decyl sulphate, hexanol or hexanoic acid) the adsorption reaches its equilibrium state in a time of the order of seconds to minutes. Higher surface activity results in greater times for establishing the equilibrium state of adsorption which sometimes cannot be realised by available experimental methods. To avoid long-time experiments, extrapolations were often carried out in order to get equilibrium values. Different extrapolation procedures as well as criteria of an equilibrium state of adsorption are discussed in the literature (cf Miller Lunkenheimer 1983). 

Several investigations were carried out to study the above transitions from common film to common black film and finally to Newton black film. For sodium do-decyl sulphate, the common black films have thicknesses ranging from 200 nm in very dilute systems to about 5.4 nm. The thickness depends strongly on electrolyte concentration and the stability may be considered to be caused by the secondary minimum in the energy distance curve (see Chapter 7). In cases where the film thins further and overcomes the primary energy maximum, it will fall into the primary minimum potential energy sink, where very thin Newton black films are produced. The transition from common black films to Newton black films occurs at a critical electrolyte concentration that depends on the type of surfactant. 

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