The sample is hydrolyzed by nascent hydroiodic acid. The iodine liberated is titrated with a standard volumetric sodium thiosulfate solution. The method is applicable to the analysis of polyethoxylated derivatives of primary saturated fatty alcohols, oleyl alcohol, satureted fatty acids, straight and branched chain alkylphenols. It is not applicable in the present of compounds containing sulfur or nitrogen, compounds containing oxypropylene group, aldehydes or acetals, sterols and derivatives.