Abstract
The influence of compn., and added salts and polyols on the stability of an oil-in-water microemulsion formulation and on the apparent pKA (apKA) of the used oleate surfactant is investigated. High temp. favors a decrease of the apKA and leads to the formation of more hydrated micelles. The apKA decreases also when the percentage of ethanol increases. Citronellol mols. do not significantly ...
Abstract
The influence of compn., and added salts and polyols on the stability of an oil-in-water microemulsion formulation and on the apparent pKA (apKA) of the used oleate surfactant is investigated. High temp. favors a decrease of the apKA and leads to the formation of more hydrated micelles. The apKA decreases also when the percentage of ethanol increases. Citronellol mols. do not significantly influence the apKA at concns. between 0% and 2% wt./wt. By contrast, with increasing limonene concn., the apKA increases.It was obsd. that anions of sodium salts destabilize the microemulsion and high temps. are needed to recover it. By increasing the concn. of NaCl, a slight increase of the apKA is obsd., which can be assocd. with a non-specific, electrostatic (Debye-Hueckel) effect. Cations of chloride salts have different effects depending on their ability to exchange with Na+ near the carboxylate group. Li+, Na+ and K+ have apparently a salting-out effect. Tetramethylammonium chloride and choline chloride have salting-in effects until resp. 0.6 and 0.4 mol kg-1. The assocns. of sorbitol or glycerol with ethanol lead to a salting-in effect and to a decrease of the apKA of Na-Oleate. [on SciFinder(R)]
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