Undergraduate student frequently ask for laboratories having some relation to industry and practical applicatiopns whereas professors want to introduce the students to fundamental theory by laboratories carried out with common inexpensive apperatus and inexpensive innocuous chemicals. At the Departement of Chemical Engineering at the Compl egrave qne Technology University in France the researches developed the experiment described here. The researches used conductivity and pH measurements on a commercial soap to determine some of its properties and to relate the properties to surfactant theory. The experiment was used after lectures on the nature properties and technical application of surfactants.