The controlled formation of stable dispersions of solid powders in liquids is of both theoretical and practical interest. The suspendibility of a powder depends upon and aids in the understanding of the surface properties of the disperse phase, as these affect, cohesion between particles in various media and as they result, in selective adsorption of ions or molecules from solution. Moreox-er many commercial products, such as paints and printing inks, consist of finely clix idecl solids dispersed in liquids. It also seems likely that the relative effectiveness of detergents may be closely related to their ability to stabilize suspensions of removed dirt.In the present work the effectixre particle-size distribution of powdered manganese dioxide was determined in a number of media to aid in ascertaining the mechanism whereby relat.ix'ely stable dispersions may be produced in aqueous solutions. The amounts remaining in suspension after a 4-hr. settling period xvere also determined as a function of concentration in aqueous solutions of Aerosol OT, Oronite, Hyamine 1622, Triton X-100, sodium oleate, and p-t.oluenesulfonic acid. Characteristically, the curxres of amount suspended vs. concentration of dispersing agent pass through a maximum at low concentrations. It seems likely that the shapes of these cuives, as well as the differences between different, detergents, are explicable in terms of varying effectix'eness in disgregation of the aggregates xvhich normally form on introducing a powder of given ultimate particle size into a pure liquid. The mechanism by xvhich this is accomplished appears to be through change in the zeta potential effected by adsorption of ions from solution. MATERIALS Baker's c.p. manganese dioxide powder was used throughout this work without further purification.Aerosol OT was obtained from the American Cyanamid Company in the form of "100%" pellets and used directly. It is the sodium salt of dioctylsulfosuccinic acid.Oronite Actix'e, made by the California Research Company, was a sample receix'ed through the courtesy of the Lever Brothers Company, and described as 1 ITesentcd at the Twenty-second National Colloid Symposium, which was held under the auspices of the Division of Colloid Chemistry of the American Chemical Society at Cambridge. Massachusetts, .June 23-2.5, 1948.

saturated alcohol. Maximum solubility seems to be obtained with both the unsaturated and hydroxyl groups close to the center of a compact molecule. The solubility also decreases with increasing molecular weight and temperature. Greensboro, N. C.

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This paper is in the nature of a preliminary report on the phase rule behavior of sodium oleate and water, there being no previous study in the literature. The purpose of this investigation was to determine whether the sequence of phases intermediate between crystalline curd fiber phase and isotropic liquid, recently discovered (17,18) in the case of anhydrous sodium palmitate also exists for sodium oleate, and, if so, to determine the

Sodium stearate, although one of the most important constituents of commercial soap, has not previously been studied from a phase rule point of view. This paper presents the results of an exploratory survey. Although this soap has not yet been investigated as extensively as sodium oleate (8), it has nevertheless been possible to construct a considerable portion of the phase rule diagram.Recent work (6,7,8,11) has shown that all the saturated sodium soaps and likewise sodium oleate pass through a sequence of mesomorphic states between room temperature and the melting point, instead of having only the single liquid crystalline form formerly recognized. Since the number of phases in this sequence is not always the same for different soaps, the generalization (1) that phase rule diagrams for different soaps do not differ from each other qualitatively must break down to some extent in the regions of concentration involving these new phases. One purpose of this work was to investigate the extent of the differences thus caused in the soap-water diagram.