The State of Metal Ion in Aqueous Solutions and its Surface Chemical Effects. III. Rheological Study for the Effect of Metal Ions on the Monolayer of Stearic Acid

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Abstract
The effect of metallic ions on the monolayer of stearic acid was studied by the rheologi-cal method. (1) It was shown that the development of visco-elastic property of the film is closely correlated with the formation of metal soap. Result obtained by the rheological measurement enables us to classify the metal ions into three groups; Li, Ca, Sr and Ba belong to the 1st, showing the formation of the condensed solid film and the rheological behavior of Voigt model; Th, Fe, Al, Co, Cu and Zn, the 2nd, exhibiting the formation of the expanded solid film and the rheological behavior of Maxwell model; Na, K, Rb and NH4, the 3rd, forming no solid film. These results were discussed in relation to the phenomena observed in the studies of the metal ion monolayer interaction, the adsorption of ion on the built-up film and the effect of ion on the wettability of a solid surface. These phenomena could be correlated with the formation of simple soap or complex metal ion-monolayer aggregate, the 1st and 3rd resulting in the former and the 2nd, in the latter. (2) It was frequently observed for the interacted film with the ions of the 2nd group that the area of solidification is larger than the limiting area estimated from the surface pressure-area curve, while in the case of the film with the ions of 1st group the values of both area coincide with each other. (3) It was shown that the monolayer of stearic acid, spread on the substrate containing ferric hydroxide sol, formed an expanded solid film. (4) It was shown for Co and Sr ions that the strength of interacted film is a measure of film-bound ion.

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