Abstract The determination is carried out by adding, at 30 degree Celsius, of distilled water to a propanol solution to the surface active agent until the appearance of cloudiness. The determination of the cloud point index provided a way of characterizing weakly alkoxylated derivates and their hydrocarbon hydrophobic groups. This simple and rapid measurement is a valuable means for checking the level of alkoxylation of non-ionic derivatives intended, for example, for sulphonation