Surface chemical behavior of polar compounds in nonaqueous liquids dispersing effect of the soap solution

Abstract A study has been made of the surface chemical behavior of fatty acid-hydrocarbon solutions in which a steel plate is dipped or iron powder immersed and which is heated to 100°C. The amount of iron soap formed in the solution gradually increased with the lapse of time. Even when the concentration of fatty acid was greatly changed, the formation of soap was not greatly affected. In the experiments using iron powder, the critical temperature for adsorption was still high, even when the concentration of stearic acid in the cetane solution decreased to as little as 4.45 · 10 −4 M . Rhodamine B was added to the liquid paraffin solution of Al stearate and Fe stearate or the solution in which the iron powder was immersed in order to measure their absorption and fluorescence spectra. It was then observed that the maximum absorption spectrum was 546 mμ, while the maximum fluorescence spectrum was 560 mμ, and further that micelles were formed in these soap solutions. The critical micelle concentration values for the liquid paraffin solution of Al stearate and Fe stearate measured by a fluorescence spectrum method were 1.05 · 10 −5 M and 4.0 · 10 −5 M respectively. Meanwhile, it was observed that the iron soap concentration of the solution in contact with the iron powder was more than the above concentration after 3 hours. The solution whose concentration had reached the above soap concentration showed a dispersing effect upon iron powder and carbon black. It can therefore be concluded that the metal soap formed in the lubricating oils will serve to disperse worn debris and other solid matter, and that an effective adsorption film can be formed by bringing about the formation of metal soap and so increasing the critical temperature.