Observations on Detergent Action of Soap Solutions : Fourth and Final Communication : Soap Solutions and Silicic Acid, Clay and Cellulose

Spring, W. Luttich. Rec. trav. chim. (1910), 29(1), 8; SciFinder (Chemical Abstracts Service: Columbus, OH); https://scifinder.cas.org (accessed July 8, 2010). see also C. A., 4, 138, 969. Study of the action of hydrated iron oxide, 7Fe2O3.3H2O on soap soln. of varying conc. led to the conclusions that the optimum suspension conc. of the soap soln. is 0.5%, that the soap splits into a basic and acid part, the basic combining with the Fe2O3 and the acid part remaining in soln., and that a soap soln. will remove Fe2O3 from its adsorption compds. with cellulose. Substituting an Fe hydrosol for the Fe2O3 it was found that pptn. occurred between limiting ratios of the soap to hydrosol, i. e., between 1 of soap to 2.16 of Fe2O3 and 1 of soap to 3.47 Fe2O3. The pptn. of Al2O3, with soap soln. shows a periodicity, the ratios of soap to Al2O3 in those solns. which become clear being approx. 8.33, 4.16, 2.06. If the wt. of Al2O3. exceeds that of the soap no pptn. occurs. A large excess of soap, 20 times the wt. of Al2O3, gives a suspension optimum, whereas 80 times the wt. of Al2O3 gives pptn. The speed of the reaction depends primarily on the ratio of the reacting substances. 7SiO2.3H2O combines with a basic constituent of soap, leaving an acid constituent of low ash in soln. The % of ash in the soap in soln. increases when more dil. soap solns. are used, due to soln. of SiO2. The adsorption compd. of basic soap with SiO2 dissociates on shaking with H2O. A pptn. optimum occurs at 1/8% soap soln., and a suspension optimum at 1/16 and 1/2%. A hydrated clay gave approx. the same results, pptg. about 60% of the soap from a 1/2% soln. The soap has a solvent action on the clay, a 1/8% soap soln. giving the highest ratio of suspended clay to soap. A suspension optimum for the settling of clay in soap soln. is found at 1/32% soap soln. Cellulose forms an adsorption compd. with the basic constituents of soap, the cleavage of the soap being noticeable only in concs. above 1%. The cleansing action of soap is due to the formation of an adsorption compd. with the material to be removed, which thus loses its adhesive properties. Reprinted with the permission of the American Chemical Society. Copyright © 2010. American Chemical Society (ACS). All Rights Reserved