非イオン界面活性剤とヨウ素との相互作用-1-

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The aqueous solutions of the nonionic surfactants consisting of polyethenoxy ether, when aqueous solution of iodine is dropped into them, become turbid. Authors named the volumes of 0.05% aqueous solution of iodine required to produce turbidness of 5ml of 0.5% surfactants solutions to be the "Iodine Number". The Iodine Number and the number of mols of ethylene-oxide added in the surfactant are in a linear relation (Fig. 1). When I and n represent the Iodine Number at 20°C and the number of mols of ethylene-oxide added in the surfactant respectively, the following relations are obtained : in octyl-phenyl series I=-0.10n+6.2 in nonyl-phenyl series I=-0.09n+6.8 in cetyl series I=-0.18n+11.2 Negative value of coefficient n means that the Iodine Number decreases with increase of the number of mols of ethylene-oxide added. The coefficients are equivalent to Iodine Number decrease caused by every one mole addition of ethylene-oxide for a homologous surfactant series. And the coefficients in octyl-phenyl and nonyl-phenyl series are nearly equal, but in cetyl series it is about double of them. The 2nd term of above equations is constant for each homologous series and corresponds to the Iodine Number of those whereby the number of mols of ethylene-oxide added is zero, and also it increases with the increase of lipophillic property of the hydrophobic radical in the surfactants series. Therefore, from these terms, it is considered that the lipophillic property decreases in the following order : Cetyl radical>Nonyl-phenyl radical>Octyl-phenyl radical Iodine Number increases rapidly with rise in temperature at titration (Fig. 2). Iodine Number increases slowly when the surfactant's concentration decreases from 0.5% to 0.25%, and increases rapidly below 0.25% (Fig. 3). When sodium chloride is added, Iodine Number increases at first, but decreases when the salt is added further beyond a maximum point (Fig. 4). In order to determine hydrophile-lipophile-balance (HLB), water number method, dimethyl-formamide method and phenol titration method are practically used at present. But in these method it is difficult to determine HLB of compounds to which higher number of mols of ethylene-oxide have been added, because these method will result to be almost the same constant for those compounds. This Iodine Number method, however, takes an advantage that it enables clear determination for HLB of higher mole adduct of ethylene-oxide by using the linear relaction between I and n. As different lipophillic radical shows different tendency, it can be utilized for the distinction of the structure of surfactants.
日本油化学会の論文

非イオン界面活性剤とヨウ素との相互作用-1-

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