ラウリル硫酸ナトリウム溶液におけるカリウムイオンの挙動
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概要
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It was found that KLS precipitates in NaLS-KCI mixtures in low NaLS concentrations, and precipitate decreases and finally disappeares as the NaLS concentration increases. As this phenomenon is important in biological systems, e.g. those involving the interaction of metal ions with micellar bile salts in solution, it was of interest to us to observe this phenomenon and to study its mechanism.<BR>The phenomenon was studied by measuring LS and potassium ion concentrations in filtrates of KCI-NaLS mixtures. As a result, the precipitation and dissolution zones were influenced by KCl concentration and temperature, and the precipitation zone was not observed above the Kraft point of KLS. It was further observed that as soon as the LS ion concentration reaches to the cmc, the KLS precipitate begins to decrease. Therefore, it was found that the dissolution zone was closely related to the micelle formation of LS ions.<BR>But it was suggested that the KLS precipitate was not solubilized in the hydrocarbon core of micelle in the dissolution zone, because KLS was hydrophobic but not oleophilic as revealed by the measurement of solubilities of NaLS and KLS in several solvents.<BR>Plot of Δκ (=the difference between the calculated conductivity of KCl+NaLS and the observed conductivity of mixtures of KCl-NaLS) against the NaLS concentration showed that Δκ increased until the maximum precipitate was reached and then decreased in the dissolution zone.<BR>The decrease in Δκ stopped at the point where the KLS precipitate disappeared and Δκ remained constant there after.<BR>Therefore, it was assumed from the above-mentioned results that the precipitate dissociates into potassium and LS ions in the dissolution zone, and LS ions take part in the micelle formation. Moreover, it was suggested that potassium ions are adsorbed on the surface of micelles because of their low hydration degree.
- 社団法人 日本油化学会の論文