Saturation Capacity of Colloids Combinations

Spring, W. Archives des Sciences Physiques et Naturelles (1911), 30, 561-71; SciFinder (Chemical Abstracts Service: Columbus, OH); https://scifinder.cas.org (accessed July 8, 2010). cf. C. A., 4, 138, 969, 1911. This is a report of some suggestive expts. on the mutual adsorption relations of saponin, lampblack and filter paper. When varying amts. of saponin are added to a standard suspension of lampblack in water the solns. of high and of low conc. settle faster than do the intermediate ones. There is an optimum stability at a conc. of saponin between 2.0 and 3.5%. In an elec. field saponin moves toward the anode, lampblack toward the cathode. When saponin is added to a lampblack suspension and an elec. current is passed the lampblack moves toward the anode-a reversal of the direction which it exhibits when alone. When a suspension of lampblack is poured through a filter the paper retains a part of the lampblack and this retained portion cannot be removed by washing with water, even when the filter is reversed. But if a soln. of saponin be poured through the blacked filter a portion of the retained lampblack is given up and passes through with the soln. A crayon made by molding a mixture of wet clay with lampblack or finely ground graphite marks paper easily and leaves a mark which is erased with difficulty. If, however, a soln. of saponin be used to moisten the clay-lampblack mixture the crayon is harder, marks paper with difficulty and the mark is easily erased. Similar results are obtained when the paper, instead of the crayon, is impregnated with saponin. When filter paper pulp is mixed with a lampblack suspension and collected on a cloth filter, the pulp retains some of the lampblack and the amt. so retained is sensibly independent of the conc. of lampblack in the original suspension. The author makes certain applications to the action of soapy substances in the cleansing of fabrics and concludes that there exists a limiting "saturation capacity in the combinations between colloids" which is analogous to the saturation of one atom by chem. combination with another. [This conclusion is quite out of accord with the existing knowledge of the form of the absorption isotherm and is not supported by the evidence presented. Reprinted with the permission of the American Chemical Society. Copyright © 2010. American Chemical Society (ACS). All Rights Reserved