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The solubility of benzene and toluene in water, and 1, 2, 4 and 8 mol/l urea-water solutions was determined at 5-10 degrees intervals from the freezing point of each solution to 55 °C. The solubilities (N: mole-fraction) were fit to parabolic equations of the form 1 $$\log N = {\rm A}(1/T)^2 + B(1/T) + C.$$ . [1] By differentiating the equation [1] with regard to (1/T) the heat of solution was obtained as follows; $$\Delta {\rm H} = - R[2A(1/T) + B].$$ . The heat of solution consists of two terms, that is, −2A(1/T) R and −BR. The coefficients A and B decreased with increasing the urea concentration in its aqueous solution. From the results the mode of action of urea on the solubility of aromatic hydrocarbons in water was ascribed to its capacities for (1) disrupting iceberg, and (2) reducing the average density of hydrogen bonds and/or making favorable interactions with hydrocarbons. [ABSTRACT FROM AUTHOR]

Dye adsorption spectroscopy has been used as a tool to determine cmc of anionic and cationic surfactants in water. The effect of pH and sodium chloride was examined on cmc. The dye was found to interact with sodium dodecyl sulfate (SDS) micelles but did not interact with cetyltrimethyl ammonium bromide (CTAB). In phosphate buffer and NaCl, the cmc of SDS in presence of dye was greatly lowered. The mode of interaction and the decrease in cmc in presence of dye is discussed in terms of induced micellization. The results were confirmed by conductometric measurement. [ABSTRACT FROM AUTHOR]

The correction to be applied to the apparent particle size as determined microscopically, on account of diffraction of light, has been considered. Two distinct cases viz. amplitude (opaque) and phase (transparent) particles have been considered, the theoretical treatment for the diffraction of light for which cases was available from literature. The treatment has been applied for particle size correction in case of spherical water-suspended particles of silver iodide, nujol, castor oil, iodobenzene and dimethylaniline. [ABSTRACT FROM AUTHOR]

The relation between the partition coefficient (Kp), hydrophilic-lipophilic balance (HLB) and effective chain length (neff) were investigated on the basis of literature data for ionic and nonionic surfactants. The effect of various types of structural modifications on the Kp and HLB of certain surfactants was considered. Using the neff concept for the substituted species, our approach is expected to make possible choice of surfactants for specific purposes in a less arbitrary fashion than up to now. [ABSTRACT FROM AUTHOR]

The effects of initial emulsifier concentration and emulsification time upon the globule size distribution of new type of emulsions, called oil-in-oil emulsions (nonaqueous systems) have been studied. The time of emulsification to reach a steady state globule size increases linearly with increasing initial surfactant concentration, upto an optimum emulsifier concentration, thereafter it remains constant. The initial emulsifier concentration has little effect on the steady state globule size distribution of nonaqueous emulsions. The values of frequency function, geometric standard deviation, geometric mean diameter, mean volumesurface diameter, and globule diameter of most frequent occurrence, of emulsions have been determined. [ABSTRACT FROM AUTHOR]

Electrophoretic mobility measurements have been carried out using droplets of four different oil-in-water emulsions in presence of electrolytes having different valent counterions. For each electrolyte three different (low) concentrations were used; at each concentration mobilities were measured for particles of varying sizes. In this manner mobilities for different values of χa, though presumably at constant values of ζ, were obtained. The ζ potentials were calculated by using the Wiersema-Loeb-Overbeek (W.L.O.) computational method, or failing this, the Overbeek analytical approximation method. Assuming suitable constant values of ζ the particle mobilities were then calculated by W. L. O. method. Also, the particles being fluid in nature, the effect, if any, of the viscosity of the fluid of the particle (rather than of the second order electrical effects such as relaxation correction) on its electrophoretic mobility was also investigated. The Booth liquid drop electrophoresis equations were used to calculate the particle mobilities, assuming suitable constant values of (i) ℵ/ℵ′ and ζ, or (ii) ζ only. In every case, the measured electrophoretic mobilities have been found to increase with increasing particle size. The effect of electrolytes is, in general, to maintain the same trend. Again, the calculated ζ-potentials have been found not to remain constant in solutions of constant electrolyte concentration and composition, but show a steady increase with increasing particle size; this is true for both the distilled water as also the electrolyte solution systems. The calculation of electrophoretic mobility, using the w.L.O. relaxation correction method, on the assumption of a suitable average (constant) value of ζ for each system shows that the calculated mobility values agree generally well with the observed values. Also, among the two liquid drop electrophoresis equations used, the simpler equation based on the assumption of interfacial layer charge distribution is found to be definitely less successful in all cases; it predicts only very slight increase of mobility with particle size. The equation based on the model of a diffuse double layer type of charge distribution inside the liquid droplet is somewhat more successful. [ABSTRACT FROM AUTHOR]

The flocculation of negatively charged benzene-in-water emulsions was governed by various metal cations viz., Na1+, Pb2+, UO22+, Cr3+ and Th4+. The anionic detergents BSS, OSS and SAS were the emulsifying agents. The flocculation studies were made by determining the zeta potentials microelectrophoretically. All the electrolytes except NaNO3 reduced the zeta potential appreciably. However, the charge reversal was observed with Th(NO3)4 only. The flocculating powers of the salts were of the order Th4+>Cr+3>UO2+2>Pb+2>Na+1. The emulsifying powers of the detergents were of the order OSS>SAS>BSS. The results were interpreted in the light of D LVO theory and the flocculation was largely found to occur in secondary minima which is by nature reversible. [ABSTRACT FROM AUTHOR]

Stable oil-in-water emulsions were prepared by the use of aluminium resinate as emulgent. The stability was determined in terms of coagulation which was brought about by inorganic salts with different cations. Coagulation of the emulsion was studied hemocytometrically and electrophoretically. Kinetically coalescence was found to be the rate determining step. Electrophoretic data were recorded as a function of electrolyte concentration. The charge reversal was observed for Th4+, Cr3+, UO22+ and Pb2+ ions. Using particle size, zeta potential and van der Waals constant, as parameters to calculate interaction energies, it was found that the DLVO theory allows satisfactory quantitative interpretation of emulsion stability. Various parameters for cationic binding were calculated at the isoelectric point of the emulsion. [ABSTRACT FROM AUTHOR]

The effect of some cationic surfactants on the stability of the xylene-in-water emulsion stabilized by dodecyl benzene sulphonate has been studied. The globules size was determined microphotographically. The stability of the emulsion system has been assessed by the measurement of electrokinetic potentials in presence of surfactants. The interaction energies have also been calculated and plotted as a function of interparticle distance. Flocculation studies were carried out hemocytometrically and values were correlated with electrokinetic potential. The flocculation and coalescence rate constants were determined separately in order to study the kinetics of coagulation of the system. The nature of adsorption of these surfactants has also been explained by calculating adsorption constants, value of van der Waals constant, number of binding sites, charge density and free energy of adsorption. [ABSTRACT FROM AUTHOR]

Finely dispersed solids specially freshly precipitated hydroxides of polyvalent metals have got the property of promoting oil-in-water emulsions. A study of the hydroxides of 11 metals as emulsifiers reveals that they yield coarse, though very stable emulsions comparable to those stabilized by macromolecules. The emulsion behaviour has been interpreted by studying flocculation, coalescence and the electrokinetic potential. The latter has been studied as a function of electrolyte, complex salts and surfactants both cationic and non-ionic. The stability of the emulsions is attributed to the strength of the interfacial film of the adsorbed hydroxides which is presumably of colloidal dimensions. [ABSTRACT FROM AUTHOR]

The role of W, aryl polyglycol ester, and G 100P, an alkyl phenyl polyglycol ether, on the stability of dilute petroleum ether in water emulsion has been studied in the light of the DLVO theory. The zeta potential of the emulsions flocculated by varying concentrations of different electrolytes, viz., potassium nitrate, strontium nitrate and aluminium ammonium sulphate, has been calculated from the mobility data obtained by a microelectrophoretic technique. With the help of these data, the interaction energy profiles were calculated by summing up the attraction and repulsion energies. The high energy barriers so obtained manifested the stability of both systems. The theoretical degrees of aggregation were calculated for varying Van der Waals constant. The electrolyte flocculation was studied haemocytometrically by counting the number of associated and unassociated droplets, and the degrees of aggregation were calculated. By interpolating the observed degree of aggregation into the theoretical curves the operating Van der Waals constant of both systems was obtained, and found to be 1 × 10−13 erg and 3 × 10−13 erg for the W and G 100P systems respectively. Stabilization due to steric hindrance was also suggested to occur in these systems and was explained by the theory of entropy stabilization. The pH measurements were carried out, and it was found that emulsions stabilized by non-ionic surfactants are not pH sensitive. [ABSTRACT FROM AUTHOR]

The stability and properties of oil-in-water emulsions stabilised by a simple non-ionic surfactant, decyldimethylphosphine oxide (DDPo) and by mixtures of DDPo with poly(vinylalcohol) and electrolytes have been investigated. For emulsion stabilised by surfactant alone the results confirm the idea that it is the high interfacial elasticity arising from adsorbed surfactant that determines stability. The variation of stability with surfactant concentration appeared to arise from the accompanying variation of the interfacial dilational modulus. Unlike simple ionic surfactants it was found that DDPo did not associate with poly(vinylalcohol) and although its addition to pVA solutions greatly improved emulsification, emulsion stability was impaired. Interfacial tension data suggested that the surfactant displaced the polymer from the interface. [ABSTRACT FROM AUTHOR]

Microemulsion regions in the system water-potassium oleate-pentanol-benzene were determined by titration and equilibrium compositions in multiphase areas were analyzed. The results showed the W/O microemulsions be inverse micellar solutions in accordance with earlier results. O/W microemulsions are related to the aqueous micellar solutions but with a more complex structure. At high electrolyte content the inverse micellar solution was in equilibrium with a dilute aqueous solution. The water solubilizing capacity of W/O microemulsions passed through a maximum with increasing soap/alcohol ratio, and excess water gave a phase transition to a lamellar liquid crystal at low electrolyte content of the water. The lamellar liquid crystalline phase showed no extremum of properties at compositions in equilibrium with W/O microemulsion of maximum water solubility and the basis for optimum stability of the inverse micellar solutions at a certain alcohol soap ratio was referred to conditions within the solution. The reason for this maximum solubilization capacity was found not to be related to intermicellar interactions but was confined to intra-micellar conditions. Of these conditions of the electric double layer were decisive. [ABSTRACT FROM AUTHOR]

The temperature induced phase inversion of Groundnut oil-in-water emulsions stabilised by blends of Tween 80 and Dimodan LS is associated with the development of multiple phase emulsion drops (W/O/W emulsion). Drops become progressively more complex in structure as the temperature rises until eventually the emulsions invert to W/O. These changes are attributed to two effects which arise from the decrease in the hydrophilic character of the Tween 80 molecules adsorbed with Dimodan LS molecules around oil drops in the initially formed O/W emulsion. The Tween 80 molecules move into the oil drops where configurational changes release water originally entrapped in the polyoxyethylene coils. This results in modifications to the interfacial layer at higher temperatures so that aqueous phase can permeate through it and into the oil drops. [ABSTRACT FROM AUTHOR]

The stability of emulsions stabilized by ionic detergents and their binary mixtures was studied and the relative emulsifying powers of detergents determined. The validity of DLVO theory to the emulsion systems was tested. Emulsions with zeta potentials less than 30 mV were flocculated rapidly. For emulsions with high zeta values the flocculation could be seen in secondary minima. Emulsion with detergent mixtures (anionic + cationic) were less stable (than emulsions prepared by the use of single detergent as emulsifier), if both the surfactants were initially present in the same phase. Stable emulsions with detergent mixtures were obtained by dissolving them in different phases. [ABSTRACT FROM AUTHOR]

The new method of hydrophobicity index (HI) calculation is described. HI values of the standard series of surfactants and two members of the examined series are only needed. The mean absolute and relative errors of the method are equal to 0.00075 and 0.07 per cent, respectively. [ABSTRACT FROM AUTHOR]

The effects of dispersed phase volume and particle size distribution on the rheology of oil-in-oil emulsions (nonaqueous systems) prepared with monochlorobenzene and ethylene glycol as disperse and continuous phases and polyoxyethylene sorbitan monooleate as emulsifier, have been studied. Experimental viscosity data obtained for nonaqueous emulsions appeared to fit the general equation ηrel=exp (aφ/1−kφ). The values of constant a have been found to be below the value of 2.5 for solid spheres and the hydrodynamic interaction coefficient k decreases with an increase in mean particle size. [ABSTRACT FROM AUTHOR]

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Ionic detergents were used in flocculating various toluene-in-water emulsions. These were found even more capable than polyvalent ions in their flocculation effect and only a very small amount was needed to cause the complete flocculation. The flocculation of negatively charged emulsion was governed by cationic detergents whereas for positively charged emulsions, the anionic detergents were used as flocculating agents. [ABSTRACT FROM AUTHOR]

Cholesterol stabilized oil-in-water emulsions were flocculated by cationic surfactants. Very low concentrations of surfactants flocculated the system completely, the flocculating values being 8.41·10−7 M, 5.96·10−7 M, 5.62·10−7 M, and 4.46·10−7 M for LPC, CTAB, CPB and CDBAC respectively. Further addition of surfactant showed marked stability. The results were based on electrophoretic measurements and interpreted in the light of DLVO theory. The efficiency of surfactants in flocculating the systems depends on their chain length. [ABSTRACT FROM AUTHOR]