GB/T 7383-2020 English PDF (GBT7383-2020)

This Standard specifies the determination of hydroxyl value in non-ionic surface active agents. This Standard is applicable to the determination of hydroxyl value (the hydroxyl value of adducts of ethylene oxide and propylene oxide of primary fatty alcohols, alkylphenols and fatty acids, and their mixtures) of aliphatic and cycloaliphatic poly alkoxy compounds, which is suitable for the determination of hydroxyl value in 10 ~ 1,000. The phthalic anhydride method is suitable for the determination of the hydroxyl value of adducts of ethylene oxide and propylene oxide of primary and secondary fatty alcohols, alkylphenols and fatty acids, and their mixtures. The acetic anhydride method is suitable for the determination of the hydroxyl value of adducts of ethylene oxide of primary and secondary fatty alcohols, alkylphenols and fatty acids, but not for the determination of the hydroxyl value of propoxylated products. The near-infrared method is suitable for non-ionic surface active agents whose hydroxyl value can be determined by the phthalic anhydride method or the acetic anhydride method. Interfering substances are as follows: ---Primary and secondary amines, amides, tertiary alcohols, thiols and epoxides generate side reactions that affect the accuracy of the method. ---Long-chain aliphatic acids and esters generate more stable anhydrides than phthalic anhydride acetic anhydride, which cannot be completely decomposed at the end of the determination. ---Other free acids cause interference due to the reaction with the sodium hydroxide standard solution, and alkalis, including certain tertiary amines, cause interference due to the reaction with the generated phthalic acid and acetic acid. The presence of epoxides interferes with the determination. If they can be removed by the low-temperature vacuum distillation method without changing the hydroxyl value, this method is still applicable. The above-mentioned treatment can eliminate free ethylene oxide that causes interfere...