Titrimetric determination of cis-3,6-endomethylene-1,2,3,6-tetrahydrophthalic (endic) anhydride and the impurity of the corresponding acid

A titrimetric procedure is proposed for the determination of endic anhydride by its reaction with piperidine (anhydride and acid groups) and triethylamine (acid groups) in acetonitrile. The procedure makes it possible to eliminate time-consuming stages of the hydrolysis of anhydride in the presence of pyridine and the dissolution of anhydride in aniline. It is demonstrated that the results of visual titration in the presence of indicators should be normalized with the inclusion of the indicator error in the determination of the total of anhydride and acid groups. © 1998 MAEe cyrillic signK Hayκa/Interperiodica Publishing.