Optimization of liquid soap formulation

Abstract

The quality of liquid soap for washing hands depends on its chemical composition, and it is evaluated by the physicochemical and functional characteristics of that product. The aim of the work is to optimize the formulation by varying the concentrations of anionic and amphoteric surfactants, as well as the concentration of the electrolyte-NaCl. As the concentrations of amphoteric and anionic surfactants in liquid soap increase, the values of density and viscosity increase. The value of the surface tension decreases with the increase in the concentration of the present surfactants, with the greater contribution to the decrease being shown by the anionic surfactant. Regardless of certain advantages that the anionic surfactant shows over the amphoteric one, the best characteristics of liquid soap are shown by the formulation that contains a combination of both used surfactants. The addition of NaCl to a liquid soap formulation has multiple significance, but also a different effect on the physicochemical characteristics at lower and higher concentrations. Functional and some physicochemical characteristics of liquid hand washing soap depend on the pH value of the formulation. As the pH value increases, the surface tension increases, so pH=5.5 is taken as the optimal pH value of liquid soap, as a compromise between the values of the measured characteristics and the pH value of human skin.