基于用酸滴定法滴定与亚硫酸钠在水溶液中反应所生成的氢氧化钠,提出了测定环氧值的方法.以环氧氯丙烷(ECH)为试验对象,令一定量的ECH与亚硫酸钠在一定体积的水溶液中反应1~2 h后,分取部分经定容至一定体积的反应溶液,用标准盐酸溶液滴定.按文中给出的公式计算其环氧值,对反应时间、反应温度和溶液的pH值对测定的影响作了试验.方法的检出限为4.5×10-5mol·L-1,还对方法的精密度和回收率进行了试验,测得相对标准偏差和回收率依次在1.3%~1.8%之间和95.9%~98.6%之间.

A new method of determination of epoxy value in aqueous solution was proposed based on the acidimetric titration of sodium hydroxide produced by the reaction with sodium sulfite.A definite amount of epichlorohydrin,used as object in the research,was taken and reacted with 1 mol·L-1 Na2SO3 solution in an aqueous medium of definite volume.After a period of 1-2 h,an aliquot of the reaction solution was taken and titrated with standard hydrochloric acid solution.Epoxy value was calculated stoichiometrically according to the formula given in the paper.Effects of time and temperature of the reaction,as well as the pH value of the reaction solution on the determination of epoxy value were studied.Detection limit of the method was found to be 4.5×10-5mol·L-1.Precision and recovery were tested,and values of RSD′s (n=7) and recovery obtained were in the ranges of 1.3%-1.8% and 95.9%-98.6% respectively.