We have investigated the effects of different concentrations of a range of surfactants on the kinetics of swelling of squalane-in-water emulsion drops by the addition of decane-in-water emulsion drops. Using a model described in detail in an earlier paper (Langmuir 1998, 14, 5402), we use the kinetic measurements to determine the product of the decane solubility C∞ (expressed as a dimensionless volume fraction) and effective diffusion coefficient D for the transport of decane between drops across the aqueous continuous phase. We address the issue as to whether the decane transfer occurs by “molecular” transport or whether the surfactant micelles present in the continuous aqueous phase act as “carriers” for the decane. We have investigated swelling rates for different concentrations of two nonionic surfactants, dodecyl hexaoxyethylene glycol ether (C12E6) and dodecyl octaoxyethylene glycol ether (C12E8), the cationic surfactant tetradecyl trimethylammonium bromide (TTAB) and the anionic species sodium dode...

Kinetics of swelling of oil-in-water emulsions stabilized by different surfactants

We have investigated the kinetics of swelling of squalane-in-water emulsion drops by the addition of decane-in-water emulsion drops. Squalane is sufficiently insoluble in the aqueous continuous phase that it cannot transfer between oil drops. Decane is able to transfer between drops and swells the squalane drops. The mixed emulsions were stabilized by the nonionic surfactant n-dodecyl octaoxyethylene glycol ether (C12E8) and were stable with respect to drop coalescence. We have made a systematic series of experiments in which the swelling rates were determined as functions of the initial drop radii, volume fractions, and oil compositions of both types of emulsions. Using a theoretical model originally developed by Ugelstad et al., the entire data set was successfully fitted with a single adjustable parameter equal to the product of the solubility of decane (C∞) and its diffusion coefficient in the aqueous continuous phase (D). The measured value of C∞D was consistent with a mechanism of decane transport i...

Kinetics of swelling of oil-in-water emulsions

Excess enthalpies at 298.15 K of binary mixtures of benzene with n-alkanes

The use of gas-liquid chromatography for the determination of thermodynamic properties.

We have used a gravimetric technique to measure the rate of evaporation of a volatile liquid in mixtures
 with a second, involatile component under conditions of controlled gas flow. A range of non-structured and
 structured mixtures were investigated in order to examine whether the rate limiting step for evaporation may switch from vapour diffusion across the stagnant gas layer above the liquid to mass transfer within the
 liquid mixture. Evaporation rates of pentane and hexane from mixtures with squalane (involatile) show excellent
 agreement with rates calculated on the basis that vapour diffusion across a stagnant gas layer is rate limiting
 and that mass transfer within the liquid mixture is fast. Hexane gelled by the addition of silica particles is
 found to evaporate at a rate very similar to that for un-gelled hexane because the equilibrium vapour pressure
 of hexane is unaffected by silica particle addition. Water evaporation rates from mixtures with the
 non-ionic surfactant n-dodecyl hexaoxyethylene glycol ether (C12E6) were found to be up to 10 times slower than calculated vapour space diffusion controlled rates owing
 to the
 slow development of concentration gradients within these highly structured liquid mixtures.

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D. H. Everett

Papers

The solubility of low-molecular-weight hydrocarbons in non-volatile liquids