Partition of bromophenol blue in toluene/water/sodium bis(2-ethylhexyl)-sulfosuccinate water-in-oil microemulsions
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The partition of bromophenol blue between oil-water interfaces and water droplets in water-in-oil microemulsions of toluene/water/sodium bis(2-ethylhexyl)sulfosuccinate was studied by a spectroscopic method at different water fractions and pH. The partition equilibrium constant, K p , between the two domains decreased considerably with an increase in the water fraction and pH. The decrease in K p with an increase in the water fraction suggests the retention of more dye molecules in water. The decrease in K p with an increase in pH has been attributed to a lower tendency of the base form to associate with the anionic oil-water interface compared with that of the acid form and to an increase in the negative charge density at the oil-water interface at a higher pH.
Key WordsAerosol OT AOT bromophenol blue partition equilibrium sulfonephthalein dye toluene W/O microemulsion
aerosol OT or sodium bis(2-ethylhexyl)sulfosuccinate
critical aggregation concentration
oil in water
water in oil
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