ETUDE COMPARATIVE DES PARAMETRES PHYSICOCHIMIQUES ET DES CONCENTRATIONS MICELLAIRES CRITIQUES (CMC) DE QUELQUES SAVONS COMMERCIALISES A KIKWIT EN REPUBLIQUE DEMOCRATIQUE DU CONGO

Soap is a daily-use product for both laundry and bathing. It is obtained by the saponification reaction of an oil with a strong base (KOH, NaOH...). In the Democratic Republic of the Congo, quality control of solid soaps is often limited to determining moisture content and total free alkali. However, the effectiveness and cleaning properties of a soap depend on several other physicochemical parameters in addition to these two. Nine laundry soaps and one toilet soap sold on the KIKWIT market were analyzed to determine not only water content and total free alkali, but also pH, alcohol- and water-insoluble matter, fat content and critical micellar concentration in accordance with documented analytical methods. pH values ranged from 10.07 to 11.60; water content from 2.65 to 28.58%; alcohol-insoluble matter from 3.57 to 24.06%; water-insoluble matter from 3.12 to 17.13%; fat from 68.35 to 80.05%; total free alkali from 2.32 to 5.56%; the critical micellar concentration (CMC) of all soaps analyzed was below 3.1g/L. This study showed that the total free alkalinity of all the soap samples analyzed was high, which in the long term can lead to adverse effects on skin or linen. CMC<3g/L values show that all soaps are soluble and effective.