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The electrophoretic mobility of sols and suspensions of silver iodide has been investigated in the presence of a series of homogeneous non-ionic detergents of the alkyl polyoxyethylene glycol monoether type. Just before the critical micelle concentration of the non-ionic detergent was reached a pronounced decrease in the mobility of the particles was observed. Adsorption isotherms of the alkyl hexaoxyethylene glycol monoethers on silver iodide powder also showed a pronounced increase in adsorption in the same concentration region. The changes were consistent with the formation of a multilayer of non-ionic detergent on the surface which caused a displacement of the electro-kinetic plane of shear away from the surface. Adsorption of non-ionic detergent at the silver iodide/solution interface inhibited the adsorption of lanthanum, barium and sulphate ions.

The flocculation of positively-and negatively-charged silver iodide sols by divalent and trivalent ions has been examined in the presence of a series of alkyl polyoxyethylene glycol monoethers. As the concentration of non-ionic detergent was increased the concentration of inorganic salt required to produce flocculation also increased. The increase in stability of the sols produced by the adsorption of the non-ionic detergents could partly be accounted for by the reduction of the attractive forces between the particles due to the presence of the adsorbed layer. Steric hindrance between the adsorbed layers of the particles as they approached, however, also appeared to contribute to stabilization.

The reversible photochemical oxidation-reduction reaction in the thionine-ferrous iron system can be made irreveraible by the removal of the reduction products of thionine from the reaction mixture. One method is to distribute the products between immiscible solvents. The purple-colored thionine dye is insoluble in ether; but its reduction products are soluble. Since ferric ions also are insoluble in ether, the two products of the reaction can be separated by extraction with ether during the illumination; some stored light energy thus can be preserved. The ether extract containing the reduction products of thionine can be caused to form a homogeneous mixture with the mother liquor by adding methyl alcohol; the back reaction will then come to completion. A galvanic cell using stored light energy can be made by placing the ether extract (with some methyl alcohol added for increased conductivity) in one compartment and the aqueous mother liquor in the other, and connecting the two compartments with an agar bridge. Potential differences of 0.2434 to 0.3585 volt were measured in this cell, depending on the concentration of the reaction products. Another method of preventing the back reaction is to precipitate ferric ions, e.g., by acetate. However, in this case the reaction cannot be reversed, and thus no direct proof of energy storage can be given. The relevance of these observations to the problem of energy storage in photosynthesis is discussed.

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