This method is applicable to the determination of the hydroxyl functions of polyoxyalkylenated condensates of aliphatic and alicyclic compounds (in particular, ethoxylated, propoxylated or mixed derivatives of primary and secondary fatty alcohols, alkylphenols and fatty acids), and allows the determination of hydroxyl incidences having values ranging from 10 to 1000. However, certain substances present in these compounds can react with phthalic anhydride or with the standard solution of sodium hydroxide used, and, therefore, dis ort the results. Possible interferences are detailed below:
——Primary and secondary amines, amides, tertiary alcohols, thiols and epoxides undergo secondary reactions, which affect the precis on of the method. — Long-chain fatty acids and esters can interfere by forming anhydrides that are more stable than phthalic anhydride, and they are not completely broken down at the end of the method.
NBN T 63-143-1980 history
1980NBN T 63-143-1980 Non-ionic surface active agents - Polyalkoxylated derivatives - Determination of hydroxyl value - Phthalic anhydride method