An improved method for determining the water number for surfactants.

Surfactants have a significant role in everyday life and various industries. Their amphipathic nature significantly influences their properties, functions, and applicability. The ratio of water and oil solubility is characterized by the HLB value (hydrophilic-lipophilic balance) or the closely related water number. A determination of the water number of surfactants represents the amount of water that a surfactant can incorporate into a microemulsion. The results of measuring the water number provide information about the hydrophilic properties of the surfactant in question. Understanding the water number helps determine the applicability of surfactants. From the water number of surfactants, conclusions can be drawn about the HLB value of the particular surfactant, providing further insights into its properties. Although a well-established method for determining water number has long been available, it has been revealed that many of the auxiliary substances and chemicals used in this process have severe health-damaging effects, leading to their discontinuation in routine laboratory use. Our goal was to find a solvent combination that would be suitable for the water number determination method. Additionally, we aimed to investigate solvents that are environmentally and human-biologically less harmful, easily and affordably obtainable.•The study presents a method for determining the water number of surfactants.•The method is straightforward to execute and free from harmful solvents.•By improving the method, we enhanced the reliability of the examination.