Observations on Detergent Action of Soap Solutions : First Communication

Spring, W. Recueil des Travaux Chimiques des Pays-Bas et de la Belgique (1909), 28, 120-35; SciFinder (Chemical Abstracts Service: Columbus, OH); https://scifinder.cas.org (accessed July 8, 2010). The action of soap is explained by the following facts: (1) Carbon hastens the decomp. of soap in water by causing the formation of an acid salt. This combination of C with the soap is not stoichiometric but a combination such as exists between colloidal substances. The combination of the C with the soap is formed because of the difference of the electrical polarity of its constituents from water. (2) C suspended in water forms a combination of absorption more or less stable with the solid substances, especially cellulose. This, the author says, is proved by the fact that a suspension of finely divided C in water will give up its C to filter paper when filtered, and if the paper is then inverted the C cannot be washed off by means of water. There exists a combination of colloidal C and paper. (3) A suspension of C in soap solution is characterized by its stability. When filtered all of the C passes through the filter paper. In his experiments the author employed a 2% soap solution and C from which all oily matter had been removed so that there was no chance for emulsions. It was found that there was an optimum % of concentration for which the C remained in suspension. In a 2% sol. the C deposited almost as rapidly as in pure water, but in solutions of less than 0.5% the deposition was slower. In a 1% sol. the C remained in suspension about 2 months. All of the soap solutions which had retained C in suspension nevertheless had a sediment. Acid and alkaline solutions of soap were tried with regard to their power of holding C in suspension. The acid solutions became clear rapidly while the alkaline held the C better than pure water does. MeOH and EtOH solutions of soap were also tried. The deposition of C from these took place more rapidly than in the case of water. Soap solutions which deposited C were examined to see whether any soap was dragged down with the C. It was found each time that the % of ash of the sol. which had been agitated with C and then filtered, was greater than the corresponding % of ash of the sol. not so treated, which was run as a comparison. The author concludes that the soap sol. was slightly decomposed by contact with the C into an acid portion which agglutinated with C and into a basic portion which remained in solution. The MeOH and EtOH sols. of soap when examined in the same manner as above showed less ash. This would mean that the solution underwent no change and that there was no agglutination with the C. This also explains why alc. solutions of soap give inferior detersive effects. The sediment of C deposited from soap solution is different in character from that deposited from pure water. It is oleaginous and viscous. A suspension of C in water was subjected to electrolysis. With a difference of potential of 8 volts cataphoresis is doubtful, but when the sol. is made slightly alkaline the C acts as if charged electropositive and is deposited around the cathode. A 0.2% soap solution when electrolyzed gave a white deposit around the anode after several hours. This, when separated from the solution and the ash determined and compared with that of the filtrate, indicates that the deposit at the anode is an acid soap while the soap left in the solution is basic. The author is carrying on experiments to show the action of silicic acid, iron oxide, Al2O3, etc., in soap solutions. Also in Arch. sci. phys. nat. g.acte.en., 27, 229. Reprinted with the permission of the American Chemical Society. Copyright © 2010. American Chemical Society (ACS). All Rights Reserved